EXPECTATIONS FOR THE LABORATORY COMPONENT OF BSC1005C
The lab is a very important part of this course. The lab grade is a combined with the lecture grade
and contributes 30% to the final grade. You are advised to take the lab very seriously.
1. Attend lab every week. Attendance is important to your success. Nothing can replace
the experience acquired by actually doing the lab. If you miss a lab, you miss the quiz or
assignment for that lab as well as the information needed for the next week’s quiz or lab
report. A new lab is scheduled each week so that missed labs cannot be made up.
2. Answer the pre-lab questions. Usually we would have completed some of the topic in
lecture before the lab so you should be able to answer the questions or at least know
where to find the answers.
3. Since labs are only once per week it is easy to forget to do assignments and prepare for
lab quizzes. The best way to avoid this is to do the lab report as soon as possible after the
lab so that you can ask for help if you need it.
4. You will be assigned to a group for lab. Working in groups is an effective way of
learning because it allows students to share knowledge and learn from each other.
However, the lab report or lab quiz is an individual exercise. Do not allow any one to
copy your assignments and do not copy from any one. This is not ‘working together’.
Usually, in this case, one person comes up with an explanation and others copy it. It is
cheating, and very easy to detect when several students have the same grammatical and
factual errors! Any work that is copied will not receive a grade. This applies to both the
persons copying and those allowing their work to be copied.
5. Some time during the semester there will be a peer evaluation of the lab groups. That is,
you and each of your group members will have an opportunity to evaluate yourself and
each other on criteria such as cooperation, preparedness for lab etc.
I have read the above laboratory expectations and understand what is required of me.
Signature: ________________________________________
1
Date: ____________
Laboratory Safety: General Guidelines
1.
THE USE OF CELL PHONES IS STRITCLY PROHIBITED FOR THE DURATION OF THE
LAB PERIOD. STUDENTS USING CELL PHONES ARE CONSIDERD TO BE ABSENT!
2.
Upon entering the laboratory, place all, books, coats, purses. Backpacks, etc in designated areas, not on
bench tops.
3.
Locate and when appropriate, learn to use exits, fire extinguisher, fire blanket, chemical shower, eyewash,
first aid kit, broken glass container, and cleanup materials for spills.
4.
In case of fire, evacuate the room and assemble outside the building.
5.
Do not eat (includes gum), drink (not even water), or apply cosmetics in the laboratory.
6.
Confine long hair, loose clothing, and dangling jewelry.
7.
Wear shoes at all times in the laboratory.
8.
Cover cuts and scrapes with a sterile, water-proof bandage before attending lab.
9.
Wear eye protection when working with chemicals.
10.
Do not taste anything or place anything into your mouth during the lab.
11.
Wash skin immediately and thoroughly if contaminated by chemicals.
12.
Do not perform unauthorized experiments.
13.
Do not use equipment without instruction.
14.
Do not remove anything from the lab.
15.
Report all spills and accidents to your instructor immediately.
16.
Never leave heat sources unattended.
2
17.
When using hot plates, note that there is not always visible sign that they are hot (such as a red glow).
Always assume that hot plates are hot.
18.
Use an appropriate apparatus when handling hot glassware.
19.
Do not allow liquid to come into contact with electrical cords. Handle electrical connectors with dry hand.
Do not attempt to disconnect equipment that crackles, snaps or smokes.
20.
Upon completion of laboratory exercises replace all materials in the areas designated by your instructor.
21.
Do not pick up broken glassware with your hands. Use a broom and dustpan and discard the glass in
designated glass waste containers; never discard with paper waste.
22.
Leave the laboratory clean and organized for the next student.
I have read the above laboratory safety rules and regulations and agree to abide by them.
Signature: _________________________________________
3
Date: ____________
EXERCISE 1
Metric Measurement & Scientific Notation
LEARNING OBJECTIVES
 Writing numbers in scientific notation.
 Use of the metric system to measure length, mass, volume and temperature.
 Conversion of metric units.
 Use of basic lab apparatus used for measurement
INTRODUCTION
Science is the process of knowing and scientists are constantly making observation and making
measures to gain knowledge and describe various features of the world around us. Measurements
allow us to understand the relative size of structures. The metric system is the universal
measurement system used in all fields of science and is used to measure length, mass, volume
and temperature. Before we go on to the metric system let us first look at scientific notation.
SCIENTIFIC NOTATION
Scientific notation is a clear and concise way of writing very large or very small, cumbersome
numbers that have many zeros. For example the distance from the earth to the sun is 149,600,000
kilometers and the size of a bacterial cell such as E. coli is 0.000000002 kilometers. Scientific
notation allows us to write these numbers in a much neater form. It is made up of one non-zero
number before the decimal point and multiplied by 10 (called the base), raised to a certain power
(called the exponent). An example of a number written in scientific notation is 1.25 x 104.
To write 149,600,000 km in scientific notation, we must first move the decimal point 8 places to
the left to obtain 1.496. (Note that where there is no decimal point, it is understood that it is after
the last digit of the number). Every time the decimal point is moved one place to the left, we are
dividing by 10, so moving it 8 places means we have divided by 100,000,000 or 108. Therefore
in order to preserve the original value of the number it must be multiplied by 108 and will be
written in scientific notation as 1.496 x 108. The exponent is the number of places moved. To
write 0.000000002 the same principle applies but this time the decimal point has to be moved 9
places to the right. Moving the point to the right means we are multiplying by 109. Therefore in
order to preserve the original value of the number it must be divided by 109, hence it will be
written as 2.0 x 10-9 in scientific notation.
General Rule: Move the decimal point enough places so that one non-zero number is in front
of the decimal point. The exponent is the number of places moved. The exponent is positive
when moved to the left and negative when moved to the right.
4
Write the following numbers in scientific notation.
1) 800,000 ___________
2) 123,000,000 ___________ 3) 0.00067 ___________
4) 0.00000000592___________ 5) 45,9000 ___________
6) 0.0000732 ___________
Write the number represented by scientific notation.
7) 2.98 x 105 ___________
8) 5.71 x 10-4 ___________
9) 6.7 x 10-8 ___________
10) 3.9 x 103 ___________
11) 2.56 x 102 ___________
6) 8.24 x 104 ___________
METRIC SYSTEM CONVERSIONS
One of the greatest advantages of the metric system is the ease of conversion. It is a decimal
system of measurements and so it is easy to convert from one unit to the next either by
multiplying or diving by 10 or multiples of 10. This means that converting between units
requires only the movement of decimal places. The metric units for length, mass, and volume
are meters, grams, and liters, respectively. The same prefixes are used for all units. For
example, the prefix kilo denotes 1,000; 1 kilometer = 1000 meters, 1 kilogram = 1000 grams,
and 1 kiloliter = 1000 liters. Table 1 lists some common metric prefixes and their values.
Table 1 – Metric System Conversions.
Prefix
Symbol
Value
Giga
Mega
Kilo
Hepta
Deka
Meter, liter, gram
Deci
Centi
Milli
Micro
Nano
G
M
K
H
D
m, l, g
d
c
m
µ
n
1,000,000,000
1,000,000
1,000
100
10
1
0.1
0.01
0.001
0.000001
0.000000001
Exponential equivalent
(scientific notation)
109
106
103
102
101
100
10-1
10-2
10-3
10-6
10-9
To convert from one metric unit to another subtract the exponents, i.e.(the from exponent minus the to
exponent) . For example to convert from Kg to mg:
Kg =103 mg = 10-3
3- -3
( )=6
5
The difference between the exponents determines how many places the decimal will be moved. If you are
converting from a larger metric unit to a smaller metric unit the difference between the exponents will be
positive. Therefore the decimal point is moved to the right. So to convert from 65 kg to mg, the decimal
point is moved six places to the right. The result will be 65, 000, 000 mg.
If you are converting from a smaller metric unit to a larger metric unit the difference between the
exponents will be negative. Therefore the decimal point is moved to the left.
For example, to convert from 97 Kg to Mg: Kg = 103
Mg = 106
3- 6
( ) = -3
The point is moved three places to the left. The result is 0.097Mg
Another example: To convert from 853 μg to cg:
ug =10-6
cg = 10-2
-6- -2
( ) = -4
The point is moved four decimal places to the left. The result will be 0.0853 cg.
Complete the following metric conversions.
13) 28nm = ___________ mm
14) 462g = ___________ kg
15) 51ml = ___________ kl
16) 8dm = ___________ m
17) 9837 kg = ___________ mg 18) 36 mm = ___________ dm
19) 6Gm = ___________ m
20) 1763nm = ___________ cm
METRIC MEASUREMENTS (LENGTH)
The metric unit for measuring length is the meter. In this exercise, you will measure the length
of various objects.
Procedure
1. Measure the length of the following objects in the units indicated:
Your index finger (cm)
Diameter of a penny (mm)
Height of your lab partner (m)
2. Area is calculated by multiplying the length x width. Measure the length and width of
your driver’s license in centimeters and the lab table in meters and find their areas.
Always record the units when you make a measurement.
Length
Width
Driver’s license
Lab table
6
Area
3. Select three small wooden blocks. Measure the length, width, and height of each block in cm
and record those values below. Volume is calculated by multiplying length x width x height.
Calculate the volumes of the 3 blocks.
Block #
Length
Width
Height
Volume
1
___________ x
___________ x
___________ =
___________
2
___________ x
___________ x
___________ =
___________
3
___________ x
___________ x
___________ =
___________
METRIC MEASUREMENTS (VOLUME)
Volume is typically measured in units termed liters. However it can be measured in cubic
centimeters (cm3 or cc). One cubic cm equals 1 milliliter. (1cm3 or cc = 1ml.)
Procedure
1.
Using the data collected in the previous section, calculate the volume of each of the three
blocks in ml and record the data below.
Volume of block 1___________ ml
block 2 ___________ ml
block 3 ___________ ml
Graduated cylinders are used in the laboratory to measure small amounts of liquid.
Obtain 3 graduated cylinders, a beaker, a test tube and a cuvette.
Note: When water is placed into a graduated cylinder or other container, it begins to climb the
sides of the container by cohesion and adhesion. Cohesion is the tendency of water molecules to
stick to each other and adhesion is the way they cling to the side of the glass container. The water
level inside the container is uneven. This is termed the meniscus. The correct volume should be
read at the lowest margin of the water level.
7
2.
Fill the beaker up to the 200ml mark and pour the water into the graduated cylinder.
What is the volume? ___________ . This discrepancy tells us that the beaker can be used
to give approximate amounts of a liquid. For accuracy and precision in the
measurement of liquid, the graduated cylinder must be used.
3.
Use the graduated cylinders to find the volume of the test tube, the cuvette and the
completely full beaker.
Test tube
Cuvette
Beaker
Volume of cube-shaped object can be determined by measuring length, width, and height and
multiplying these together. The volume of irregularly shaped objects, like a screw, can not be
measured in this way. Another technique, known as water displacement, permits volumes of all
objects to be calculated.
4.
Measure the volume the three irregularly shaped objects using water displacement.
Place some water into the graduated cylinder. Note the amount. This is your initial volume.
Gently place the object into the graduated cylinder so that there is no splashing or loss of water.
The level of the water will rise. Note the new level. This is your final volume. Subtract the
initial volume from the final to get the volume of your object in ml.
Initial volume
Final volume
Object 1
Object 2
Object 3
8
Volume of object
METRIC MEASUREMENTS (MASS)
Mass is a measure of the amount of matter that an object has. Mass differs from weight in that
weight is the force gravity exerts on an object. Therefore, the mass of an object stays constant,
but weight can change if gravity changes. For example, the moon’s gravity is roughly 1/6 that of
the earth’s. A person weight 180 lbs. on earth would weigh 30 lbs. on the moon. Since mass is
constant, a person with a mass of 82 kg would have that mass on earth or on the moon.
The Density of a material is calculated by the dividing the mass by the volume. (D=M/V)
The mass is always measured in grams and the volume in ml (cc).
Procedure
1.
Using a triple-beam balance, calculate the mass of the three objects indicated.
Mass (g)
Volume (ml)
Density (g/ml)
METRIC MEASUREMENTS (TEMPERATURE)
Scientists measure temperature using the Celsius or centigrade scale, which is based upon the
freezing and boiling points of water. The Fahrenheit scale is not used in science. Water freezes
at 0°C (32°F) and boils at 100°C (212°F).
9
Converting from Fahrenheit to Celsius requires using the following equation:
°C = 5/9 x (°F – 32)
°C = 0.56 x (°F – 32)
or
Converting from Celsius to Fahrenheit requires using the following equation:
°F = (9/5 x °C) + 32
or
°F = (1.8 x °C) + 32
Procedure
Using the Celsius thermometer provided, measure the temperature of the following and then use
the equation above to convert each into Fahrenheit.
Temp. in Celsius
______________
______________
______________
______________
______________
_______________
Room temperature
Surface of skin
Ice water in beaker
Boiling water
Tap water
Today’s temperature
Temp. in Fahrenheit
______________
______________
______________
______________
______________
______________
PRACTICE PROBLEMS
Complete the following problems.
Write the following numbers in scientific notation.
1) 7000 ___________
2) 51,800___________
4) 8,000,000 ___________ 5) 234,000 ___________
7) 0.0089 ___________
3) 465,000,000 ___________
6) 0.000003 ___________
8) 0.00000239 ___________ 9) 0.0045 ___________
10) 567,000,000 ___________
Write out the numbers represented by scientific notation.
11) 8.0 x 103 ___________ 12) 4.23 x 108 ___________
13) 9.21 x 10-4 ___________
14) 9.27 x 10-9 ___________
15) 1.5 x 104___________
10
Complete the following metric conversions.
16) 4.5 cm ___________ mm
17) 63 kg ___________g
18) 28.6 l ___________ml
19) 1.45 mm ___________ cm
20) 98.2 nm ___________mm
21) 7.8 g ___________ mg
22) 89.2 ml ___________ l
23) 34.8 nm ___________ cm
24) 28.5 cm ___________km
25) 78.9 km ___________ m
26) 30.6 cm ___________ mm
27) 45.0 nm ___________mm
28) 23.8 kg ___________mg
29) 76 ml ___________ l
30) 58.5 g ___________mg
Metric Conversions
Metric to American
Standard
American Standard
to Metric
Length
1 mm = 0.039 inches
1 inch = 2.54 cm
1 cm = 0.394 inches
1 foot = 0.305 m
1 m = 3.28 feet
1 yard = 0.914 m
1 m = 1.09 yards
1 mile = 1.61 km
Volume
1 ml = 0.0338 fluid ounces
1 fluid ounce = 29.6 ml
1 L = 4.23 cups
1 cup = 237 ml
1L = 2.11 pints
l pint = 0.474 L
1L = 1.06 quarts
1 quart = 0.947 L
1L = 0.264 gallons
1 gallon = 3.79 L
Mass
1 mg = 0.0000353 ounces
1 ounce = 28.3 g
1 g = 0.0353 ounces
1 pound = 0.454 kg
1 kg = 2.21 pounds
11
Temperature
To convert temperature:
9
°F = 5 C +32
5
°C = 9 (F – 32)
12
EXERCISE 2
pH AND BUFFERS
LEARNING OBJECTIVES:
 Become familiar with the pH scale.
 Determine the pH of different substances using a pH indicator.
 Learn to use the pH meter.
 Determine experimentally which antacid works best at neutralizing excess stomach
acid.
Introduction
pH (potential of hydrogen) is a measure of the free hydrogen ions (H+) in a solution. Pure
water is called a neutral solution because it has equal numbers of the positively charged H+
ions and the negatively charged hydroxide ions (OH-). An acid has more H+ ions than OHions while a base (also called an alkali) has fewer H+ ions than OH- ions. Although most of
the areas of our body tend to be in the neutral range e.g. the pH of blood is between 7.3 and
7.5. pH buffers present in our cells keep the pH within the neutral range. However, the pH
of the stomach is very low, between pH 1.0 and 3.0. The pH scale is used to measure pH of
a solution and ranges from 1 to 14, with a pH of 1 being the most acidic and a pH of 14 the
most basic. Refer to the pH scale below.
Figure 1 pH scale.
13
PART A: MEASURING PH
pH Indicators
pH indicators are chemicals, which display characteristic color changes in response to the
pH of standard buffer solutions. Some pH indicators used in the lab are: litmus,
phenolphthalein, methyl red, and phenol red, to name a few. These are available in liquid
form as well as paper strips. Hydrion (a type of so-called universal indicator) is one such
paper indicator that will allow you to read from pH 1 to 14. To read the pH, compare the
color change to the color chart provided.
Procedure
Using only the pipette in the beaker containing the substance to be tested, place a few
milliliters of the solution into a watch glass. (DO NOT SWAP PIPETTES). Dip a small
strip of the pH indicator into it and observe the color change. Match the color of the
indicator paper with the color chart and record the pH.
Record your results in the table below.
Table 1: pH of some common substances
Substance
pH
Acidic or Basic?
Ammonia solution
Aspirin solution
Baking soda
Banana
Bleach
Coffee
Detergent
Distilled water
Milk
Milk of magnesia
Lemon juice
Orange juice
Soda pop
Vinegar
14
pH meters
pH indicator s give us a general idea of the pH of the solution. To get a more accurate
reading of the pH, an instrument called a pH meter can be used. It makes use of an
electrode, which is immersed into the solution to be measured, and the pH is registered on a
monitor.
Use the pH meter to measure the pH of solutions X and Y.
pH indicator paper
pH meter
Acidic or basic?
pH of X
pH of Y
PART B: EVALUATING SOME ANTACIDS
Introduction
The very acidic condition in the stomach aids in the digestion of food. Sometimes the
stomach produces too much acid, which can cause discomfort. A common remedy is to
chew an antacid tablet. Antacids work by neutralizing excess hydrogen ions and are thus,
considered buffers. A buffer is any substance that can remove or accept hydrogen ions in
order to stabilize the pH of a solution.
In this experiment you are going to evaluate 4 different antacids is to determine which one
works best at neutralizing excess stomach acid. We will use an acid solution of the same
pH as stomach acid.
Procedure
1.
Use a mortar and pestle and grind up about 3 tablets of antacid.
2.
Weigh out 4 grams of antacid powder.
3.
Use a measuring cylinder, measure out 200ml of acid solution and pour the acid
into a 400ml beaker.
4.
Take the beaker containing the acid to the pH meter. Start the magnetic stirrer. You
will need a timing device.
5.
Immerse the electrode into your acid solution, making sure that it is in the solution
and not in the vortex created by the stirrer.
15
6.
Allow the pH meter to read ‘stable’ then record the pH of the acid solution. This is
your initial or starting pH.
7.
Pour the antacid powder into the acid solution. Start timing as soon as you begin
to add the powder.
8.
Record the final pH (when the pH meter reads ‘stable’ again) and the time taken to
get to that pH.
9.
Rinse the electrode of the pH meter thoroughly with distilled water. (Handle with
care!). Leave the electrode immersed in the storage solution.
10.
Wash the mortar and pestle and dry well.
11.
Repeat the experiment for the other antacids.
12.
Record your results in the table below.
Antacid
Initial pH Final pH
Difference in pH units Time elapsed
(minutes)
Lab Report
16
pH AND BUFFERS
1.
From your results, what is the difference in the H+ content between lemon juice and
household ammonia?
___________________
From your results in Table 1, rank the following in order of their H+ content (from
the one with the most H+ ions to the one with the least).
Lemon juice, orange juice, milk, distilled water, coffee, baking soda, ammonia.
Most H+ ions
Least H+ ions
2.
Use your results from the antacid experiment to answer the following questions.
Antacid
Difference in
Initial pH Final pH pH units
Time
elapsed
Rate of acid
neutralization/
pH units per
minute
a.
Calculate the rate of acid reduction by each of the antacids and record your
results in the table above.
b.
At the end of the experiment which antacid solution still had the highest
number of H+ ions? ________________
c.
At the end of the experiment which antacid solution had the lowest number
of H+ ions? ___________________
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3.
d.
Which antacid neutralized the acid slowest? (rate!) ____________________
e.
Which antacid neutralization the acid fastest? (rate!) ___________________
Suggest one reason why this method may not be ideal for comparing all antacids.
___________________________________________________________________
___________________________________________________________________
4.
State five variables that must be kept constant (the same) in this experiment.
_______________________________________
_______________________________________
_______________________________________
_______________________________________
_______________________________________
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EXERCISE 3
Carbon Compounds
LEARNING OBJECTIVES


Perform diagnostic tests to detect the presence of reducing sugars (Benedict’s),
starch (Lugol’s), protein (Biuret), lipid (SudanIV) and sodium chloride (silver
nitrate).
Identify which substances are present in an unknown mixture using these
diagnostic tests.
INTRODUCTION
The organic molecules of life are carbohydrates, lipids, proteins and nucleic acids. Each
of these groups of molecules is responsible for specific important roles in living cells.
Give 2 functions of each of these compounds in living cells:
Carbohydrates
________________________________________________________________________
________________________________________________________________________
Lipids
________________________________________________________________________
________________________________________________________________________
Proteins
________________________________________________________________________
________________________________________________________________________
Nucleic acids
In this exercise some simple chemical tests will be used to identify the presence of
members of these groups of organic compounds. (There are no simple tests for nucleic
acids that we can perform in this lab).
19
CARBOHYDRATES
Three types of carbohydrates are commonly founding living cells: monosaccharides,
disaccharides and polysaccharides.
Give an example of each type:
Monosaccharide__________________________
Disaccharide_____________________________
Polysaccharide____________________________
Some monosaccharides are called reducing sugars. They react with a blue reagent called
Benedict’s solution to form a colored precipitate (a solid that settles out of the solution)
Sugars that do not react with Benedict’s are called non-reducing sugars. Polysaccharides
do not react with Benedict’s, but will react with another reagent called Lugol’s iodine.
TESTS FOR CARBOHYDRATES
1.
Benedict's Test for Reducing Sugars
In the Benedict's test, the sample is heated with the Benedict's reagent. If
reducing sugar the precipitate forms. The color of the precipitate can range from
green, to yellow, orange, red or brown. The color depends on the amount of
reducing sugar present in the sample, with brown being the most concentrated.
Procedure
1.
Mark a clean test tube to identify the sample being tested.
2.
Add 2 ml of the sample and 2 ml of Benedict’s reagent in the tube.
Record the color of the solution in the tube. This is your initial color.
3.
Heat the tubes in a hot bath. Remove the tubes in which the color
changes. If there is no immediate color change, allow the tube to
heat for 5 minutes.
4.
Record results in Table 1 below.
Table 1 – Results of Benedict’s for reducing sugars.
1
Water
2
Starch
3
Glucose
4
NutraSweet
5
Sucrose
6
Onion
juice
Initial
color
Final
color
20
7
Potato
slice
8
Milk
9
10
Fructose Apple
solution juice
11
Honey
Explain in your own words why some of the colors changed after heating the solutions and
why others did not.
_________________________________________________________________________
_________________________________________________________________________
Why is it important to have a tube with just water in it?
_________________________________________________________________________
Sucrose is a sugar. Why did it not form a precipitate with Benedict’s?
_________________________________________________________________________
2.
Lugol’s Iodine Test for Starch
Starch reacts with Lugol's Iodine solution (iodine-potassium iodide, I-KI) to
produce a complex of starch and iodine with an intense blue or black color.
Procedure
1.
Obtain a clean white spot plate.
2.
Place one drop of the sample solution in a depression in the spot plate.
Use a small piece if it is a solid. Your initial color is the color before you
add the Lugol’s.
3.
Add one drop of Lugol's I-KI solution to the drop of sample.
4.
Note any color change.
5.
Record results on Table 2 below.
Table 2 – Results of Lugol’s test for starch
1
Water
2
Starch
3
4
Glucose Rice
5
Sucrose
6
Onion
juice
Initial
color
Final
color
21
7
Potato
slice
8
Milk
9
10
Pasta
Bread
11
Yuca
Why did some of these chemicals react with the Lugol’s iodine and others did not?
_________________________________________________________________________
_________________________________________________________________________
Which substance is your positive control? Negative control?
_________________________________________________________________________
LIPIDS
Lipids e.g. fats, are compounds that are non-soluble in water (non-polar). They also tend
to be less dense that water and so will float on it. Triglycerides are the most common
form of fats found in nature and are made up of glycerol and three fatty acids.
What does the term hydrophobic mean?________________________________________
How do saturated lipids differ from unsaturated lipids?
_______________________________________________________________________
_______________________________________________________________________
Sudan IV Test for Lipids
Sudan IV is a dye that will dissolve only in non-polar solvents, such as oily
hydrocarbons or lipids. If a liquid is mixed with Sudan IV dye and the solution turns
red then it can be assumed that the liquid was a lipid or hydrocarbon. Typically this
would be an oil, but Sudan IV will also dissolve in non-oily hydrocarbons such as
acetone and alcohol. The Sudan IV reagent that you will use has been dissolved in
alcohol to make it easy for you to handle. If fat is present in any of the substances you
test, the Sudan IV will dye it red and it will be seen floating as a red layer.
Procedure
1.
Mark a clean test tube to identify the sample being tested.
2.
Add 2 ml of the following substances to each tube.
Water
Vegetable oil
Hamburger juice
Salad dressing
22
3.
Add 2 ml of water to each tube.
4.
Add five drops of the Sudan IV solution.
5.
Mix each tube by agitating from side to side.
6.
Record results in Table 3 below.
Table 3 – Results of Sudan IV test for fats.
Water
Vegetable Oil
Hamburger juice
Salad dressing
Positive
red layer?
What do your results tell you about each of the samples you have tested?
_________________________________________________________________________
_________________________________________________________________________
PROTEINS
Proteins are the most abundant of all the organic molecules found in the cell. They are
made up of amino acids which are bonded together by peptide bonds to form chains
called polypeptides.
Biuret Test for Proteins
The Biuret reagent reacts with peptide bonds and so is an indication of the presence
of proteins. Biuret is sensitive to even a few peptide bonds. Consequently, when
Biuret reagent is mixed with a solution containing proteins (with many peptide
bonds) a strong reaction occurs that produces a violet color. Because the Biuret
reagent is blue, it is sometime necessary to look carefully to make sure that the
reaction mixture is actually violet or purple and not just an intense blue. Holding the
solution against a white background may be helpful.
Procedure
1.
Mark a clean test tube to identify the sample being tested.
2.
Add 1 ml of the sample to the tube followed by 2 ml of Biuret reagent.
23
3.
Place a piece of parafilm over the mouth of the test tube with your
thumb over it and shake vigorously.
4.
Allow the tube to sit at room temperature for 3 minutes.
5.
Note any color change.
6.
Record results in Table 4 below.
Table 4 – Results of Biuret test for protein.
Distilled
water
Egg
albumin
Milk
Hamburger
juice
Amino
acid
Gelatin
Color
present
Protein
present
Which sample do you think contained the most protein? Why?
_________________________________________________________________________
What was the final color of the amino acid sample? Explain why.
________________________________________________________________________
_________________________________________________________________________
SODIUM CHLORIDE
Sodium chloride is an inorganic substance and is very important in living cells.
Silver Nitrate Test for Salts
The silver nitrate reagent is a mixture of silver nitrate with dilute nitric acid. Handle
this solution with care! If any gets on your skin wash immediately with lots of water.
The skin areas contacted by silver nitrate solution will darken but will return to
normal in about a day. Minor exposure of this type is not harmful.
Silver test detects the presence of certain chloride ions. As chloride ions are most
commonly encountered in water solutions (e.g. sodium chloride is sea salt/table
salt), we will be looking manly for chloride ions as an indication of salt.
The addition of a few drops of silver nitrate reagent to a water solution will
immediately produce a milky-white precipitate which will be intense and persistent
if the solution has a significant concentration of chloride ions. If no precipitate
whatsoever is seen, the solution must have a solute free of chloride ions.
24
Procedure
1.
Mark a clean test tube to identify the sample being tested.
2.
Place l ml of the sample into the test tube.
3.
While carefully observing the tube, add 2 drops of the silver nitrate
reagent to the sample. (Note the possible formation of a white
precipitate. The precipitate may or may not form and may or may
not persist, depending on the concentration of ions. If chloride ions
are abundant, the white precipitate will persist and make the sample
cloudy).
4.
Record results in Table 5 below.
Table 5 – Results of test silver nitrate test for chloride ions.
Water
Salt
solution
Salad
dressing
Meat
juice
Starch
Albumin
Apple
juice
White
precipitate?
Lab Report
CARBON COMPOUNDS LAB DATA SHEET
1.
Use this sheet to summarize the results of all your tests. Use the symbols shown. (If
you did not perform the test on a substance leave the box blank).
Positive: +
Negative: –
Sample
Distilled water
Albumin
Amino acid
Apple juice
Bread
Fructose solution
Gelatin
Glucose solution
Honey
Meat juice
Benedict’s
test
Biuret test
Lugol’s
Iodine test
25
Silver Nitrate
Sudan IV test test
Milk
NutraSweet
Onion juice
Pasta
Potato
Rice
Salad dressing
Sodium chloride
Starch solution
Sucrose solution
Vegetable oil
Yuca
Unknown # A
Unknown # B
Unknown # C
26
2.
Summarize the tests you performed in the table below:
Test
Reducing sugar
Reagent used
Description of positive result
Starch
Lipid
Protein
3.
Why was a water sample included with each test?
___________________________________________________________________
27
EXERCISE 4
Microscopy & Cells
LEARNING OBJECTIVES
 Learn to use a compound microscope
 Make basic slide preparations (wet mounts).
 Distinguish between plant and animal cells based on microscopic observations of their
structures.
 Microscopic observation of bacterial cells
 Observation of some other eukaryotic cells: microscopic algae and protists.
Answer these questions before you come to lab:
1.
What are the three components of the cell doctrine?
___________________________________________________________________________
__________________________________________________________________________
__________________________________________________________________________
2.
Name the two types of cells found in the living world.
__________________________
__________________________
3.
State three differences between these types of cells
_________________________________________________________________
_________________________________________________________________
_________________________________________________________________
4.
State the four structures that are common to all cells.
_______________________
_______________________
_______________________
_______________________
28
5.
State three differences between plant and animal cells.
______________________________
________________________________
______________________________
PART 1: THE COMPOUND MICROSCOPE
Care and maintenance of a microscope

Always treat your microscope with care. When moving the microscope, use two hands.
Grasp the arm of the microscope with one hand and support the base with the other
hand. Do not swing it!

The lens surfaces must be treated with great care, as they can easily be scratched or
chipped. Use ONLY lens paper to remove dust if needed. NEVER use paper towels,
handkerchiefs, shirt tails, Kleenex, alcohol, or blow moist air onto any lens as a way
of cleaning it.

At the higher magnifications, always refocus with the fine adjustment only. Never use
the coarse adjustment at high power. If you do, you run the risk of smashing the
objective into the slide and causing irreparable damage to both! Course adjustment
should only be used during initial focusing with the low power objective.

Do not force anything-lenses, knobs, levers- ask for help.

Before storing the microscope, turn the objectives to the lowest power. Clean all
lenses with lens paper. Remove all slides from the stage. Secure the power cord, and
replace the microscope in the cabinet with the eyepieces facing inwards.
29
A.
Identifying the Parts of the Microscope
This type of microscope is called a compound light microscope. Compound, because it uses
two lenses to magnify and show details of specimens that are too small to observe with the
naked eye. The purpose of a microscope is mainly magnification. One of the lenses is in
the eyepiece and the other is the objective lens. The microscope uses light as the
source of illumination of the specimen.
Locate all the parts of the microscope as your instructor describes them:
Eyepieces: The eyepiece contains the ocular lens system and is one of the two lenses used
for magnification. Engraved on the side of the ocular lens you will see its
magnification. What is the magnification of your ocular lens system? _____
Nosepiece: This is a revolving circular mechanism that holds the different objective lenses.
Rotating the nosepiece changes the objective lens. The objective lens is in place when it is directly
over the stage and you will hear a click when it is in place.
Objective lenses: T h e s e a r e i n d i v i d u a l l e n s e s a t t a c h e d t o t h e n o s e p i e c e . A
magnification number is indicated on each objective lens. Your objective magnification values
are ________________, ______________, _______________, and______________.
Total Magnification: To obtain the total magnification produced by both the objective and
ocular lenses, you simply multiply the two values.
Eyepiece
Magnification
X
X
X
X
Objective Lens
Magnification
Scanning
Low power
High power
Oil immersion
X
X
X
X
Total
Magnification
X
X
X
X
Note: The oil immersion lens is not used in an introductory biology lab. DO NOT ATTEMPT
TO USE IT AND DO NOT PUT IT IN PLACE.
Stage: Also called the mechanical stage. This is the surface that supports and secures the slide
with the help of the stage clips.
Stage Controls: these are usually located on the side of the stage. Front/back controls move the
slide front to back and vice versa. Side/side controls move the slide from side to side.
Condenser: This is located under the stage and focuses the light form the lamp through a hole in
the stage and onto the specimen. It can be used to adjust the quality and amount of light passing
through the specimen. There is a condenser adjustment knob that may be used to raise or lower
the condenser.
30
Iris diaphragm: Located under the condenser, this is used to adjust the intensity of light passing
through the specimen. It is opened or closed using the iris diaphragm lever.
Coarse-Adjustment Knob: This large knob, located on the arm, adjusts the distance between
the stage and the objective lens in large increments. It is used initially to bring the specimen into
focus. It is dangerous to use this knob when the objective lens is already near the slide. It should
be turned very slowly to avoid breaking the slide.
Fine-Adjustment Knob: This is the small knob attached to the coarse-adjustment knob. It
adjusts the distance between the stage and the objective in small increments. It is typically used
after the objective lens is already near the slide and the specimen is almost in focus. It should be
turned very slowly to avoid breaking the slide.
Lamp: Light source located under the condenser. There is a switch to turn it on and off.
Rheostat: Regulates the intensity of the light (‘light dimmer’).
B. Label the parts of the microscope:
31
C. Learning to focus the microscope
1. Plug in the microscope, turn on the light, open the iris diaphragm and raise the condenser.
Rotate the nosepiece so that the scanning objective (4X) is in place over the stage.
2. Obtain a prepared slide of the letter e.
3. Place the slide on the stage so that the label is on your left. What is the orientation of the
e? Is it upside down or the right way it? (Look at it on the stage on, we are not looking
down the microscope yet).
4. Using the stage controls, move the slide so that the e is directly in the center of the circle
of light.
5. Using the coarse adjustment, while looking down the microscope through the eyepiece
(use both eyes), bring the stage up towards the objective until you can see the e. Bring it
into as sharp a focus as you can with the coarse adjustment knob and then fine tune with
the fine adjustment knob.
6. What is the orientation of the e now? Move the slide to the right. Which way does it
appear to move? This is called inversion and refers to the fact that the image you see
under the microscope is not only inverted but also reversed.
Sketch the e in the space below: Magnification?
7. Increasing magnification: The system of objectives is constructed so that they
are parfocal. Parfocal means that an object remains relatively in focus when you
change objectives. The area of the microscope slide that can be viewed through the
microscope is the field of view. When you switch from a lower magnification
objective to a higher magnification objective, the size of your field of view under the
microscope is greatly reduced. Therefore, always center the object under observation in
your microscope field of view before changing objectives. This will reduce the
chances that you "lose" your specimen somewhere outside the field of view. Note:
The greater the magnification, the smaller the field of view.
32
8. Move your e until it is centered in the field of view and in focus, with the 4X
objective in place. Next, carefully rotate the nosepiece until the l o w p o w e r ( 10X)
objective is in place. Focus.
Sketch its appearance in the space provided: Magnification?
9. Center the e again and move the nosepiece so that the high power (40X) is in place.
Focus. What is the magnification of your specimen? Describe what you see and explain
why this is all that you can see at this magnification.
_________________________________________________________________________________
_________________________________________________________________________________
10. Depth of focus: Obtain a slide o colored threads. Find a point with the low power
where the threads intersect. Slowly focus up and down. Notice that when one thread is in
focus, the others seem blurred. The vertical distance that remains in focus at one time is
called the depth of focus. Switch to high power and notice that the depth of focus is more
shallow (decreases) with high power than with low power. Determine the order to the
threads and complete the chart below.
Order of threads
Depth
Top
Middle
bottom
Thread color
PART 2: OBSERVATION OF CELL STRUCTURE
Now that we know how to use the microscope we will use it to observe some different types of
cells. Many of the organelles in cells are much too small to be seen with the magnifications
33
available on these microscopes. Observe and record all of the structures that you can see in each
of the cells. Also note any differences between the cells that you observe. To view the cells
under the microscope we first have to place the specimen on a slide by making a temporary wet
mount.
Exercise 1: Plant Cells
Making a Temporary Wet Mount of Elodea (water plant)
1.
Place a drop of water in the center of a microscope slide.
2.
Using tweezers pick up a leaf of Elodea and place it in the drop of water.
3.
Hold a cover slip between your thumb and index finger to one side of the specimen
at about a 45° angle. Slide the cover slip toward the drop of water and specimen
until it contacts the drop of water.
4.
Gently lower the cover slip onto the specimen and the drop of water, trying to avoid
large air bubbles. Air bubbles appear as black rings under the microscope and are
often mistaken for something more exciting! More water may be added at the edge of
the cover slip if needed to fill in any air spaces.
5.
The specimen is now ready to place on stage for observation with the microscope.
6.
View under all magnifications, starting with 4X.
7.
Sketch what you observe under 100X or 400 X total magnifications in the space below.
You only need to draw four or five cells accurately.
Label the cell wall, chloroplasts, and the cytoplasm.
34
100X
400X
Onion cells
1. Make a temporary wet mount of s m a l l p i e c e o f onion skin. U s e s k i n o n l y d o
n o t i n c l u d e a n y o f t h e t i s s u e f r o m t h e o n i o n . T he thinner your specimen,
the better the cells will be seen. Use a drop of iodine to make the mount.
2. Sketch what you observe under 100X or 400 X total magnifications in the space below.
You only need to draw four or five cells accurately.
Label the cell wall, cytoplasm, and the nucleus.
100X
400X
How are these two kinds of plant cells different?
________________________________________________________________________
________________________________________________________________________
How are they the same?
35
________________________________________________________________________
________________________________________________________________________
Why are chloroplasts absent in the red onion cells?
__________________________________________________________________________
Exercise 2: Human cheek cells
1.
Gently scrape the inside of your mouth with a toothpick to obtain epithelial
cells.
2.
Swirl the toothpick in a drop of drop of methylene blue on a clean slide.
3.
(Dispose of toothpick and cheek cell slide in the disinfectant solution.)
4.
Carefully add a cover slip as described above and examine the mount at all levels
of
magnification.
5.
Draw four or five cells at highest magnification, labeling the cell membrane,
cytoplasm, and nucleus.
400X
How are these cells similar to and different from the onion cells and the Elodea cells?
______________________________________________________________________
______________________________________________________________________
______________________________________________________________________
36
Exercise 3: Prokaryotic Cells-Bacteria
Prokaryotic cells, for example, bacteria are extremely small ranging in size from lµ to
20µ.
(How many micrometers (µ) are there in 1 millimeter? ______________)
Like, plants most bacteria possess a rigid cell wall that surrounds the cell membrane and
helps the cell maintain its shape and prevents it from bursting. Inside the cell membrane, the
cytoplasm contains ribosomes, DNA region, and storage granules. However, they have no
membrane-bound organelles like eukaryotic cells.
Bacteria are often classified according to their shape:
1. Coccus (spherical cells): Streptococci, which consist of chains of spherical cells, are
associated with strep throat. (plural, cocci)
2. Bacillus (rod-shaped): Escherichia coli, found in the intestines of humans.
3. Spirillum (spiral-shaped): Borrelia burgdorferi, cause of lyme disease.
Since bacteria are so small in order to view them we have to magnify them 1000x. Observe
the demonstration microscopes and draw the shapes of the bacterial cells below.
Coccus 1000x
Bacillus1000x
Spirillum 1000x
Exercise 4: Survey mixture
Place a drop of the mixture o f m i c r o s c o p i c a l g a e on a slide with a cover slip and
observe. Sketch the appearance of three different types of cells and identify them using the
chart provided.
37
REVIEW QUESTIONS
1.
What happens to the field of view and depth of field when you increase
magnification?
____________________________________________________________
2.
If the ocular had a magnifying power of 10X and the objective had a magnifying
power of l0X, what would be the total magnification of an object viewed through
these lenses be?
________________________
3.
Why is it necessary to center the specimen in the field of view before switching to a
higher power objective lens?
__________________________________________________________________
4.
Which adjustment knob is never used with the high power objective in place (fine or
coarse)? _______________________
Why not? ____________________________________________________________
5.
List four things you should do before putting away your m i cros cope away.
_____________________________________________________________
_____________________________________________________________
_____________________________________________________________
_____________________________________________________________
6.
Which organelles d i d y o u s e e with the magnification available?
_______________________________________________________________
7.
You are trying to view a specimen under the microscope and have the following
problems. Describe specifically how you would adjust the microscope to get a better
view of the specimen in each case:
There is not enough light
___________________________________________________________________
The specimen is blurred
38
____________________________________________________________________
The specimen is not in the center of the field of view
_____________________________________________________________________
8.
From your observations, give 3 differences between a cell of Elodea and an onion
cell.
Use comparable features!
Elodea cell
Onion cell
i.
ii.
iii.
9.
Give 3 differences (observed) between the Elodea cell and the cheek cell.
Elodea cell
Cheek cell
i.
ii.
iii.
39
10.
Why did we have to use the 100X objective to view the bacterial cells but not
the others?
EXERCISE 5
Enzymes
LEARNING OBJECTIVES
 Demonstrate enzyme activity by the hydrolysis of starch by amylase.
 Determine the effect of different temperatures on the rate of starch hydrolysis.
 Determine the effect of different pHs on starch hydrolysis.
 Demonstrate the presence of the enzyme catalase in living tissues
 Compare the relative amounts of catalase in different tissues.
 Demonstrate that oxygen is produced when hydrogen peroxide is decomposed by
catalase.
Answer these questions before you come to lab:
1.
Define each of the following terms:
Catalyst
Activation energy
Enzyme
Substrate
Product
Denaturation
Hydrolysis
Metabolism
40
2.
Why do living cells need enzymes?
_____________________________________________________________________
_____________________________________________________________________
INTRODUCTION
Enzymes are proteins folded into their tertiary structure which give them a particular 3dimensional shape. This highly specific folding creates a groove in the enzyme molecule, called
the active site. The active site has a very specific shape which only one substrate (with a
complementary shape) can bind. Any condition that causes the enzyme to unfold and lose its
shape will result in its inability to function.
An example of an enzyme is amylase, found in human saliva and also in germinating seeds. Its
substrate is the polysaccharide starch. Amylase catalyzes hydrolysis of starch to the disaccharide,
maltose.
H 2 0 + amylase + starch → + amylase-starch complex→ maltose+ amylase.
In this lab we will investigate how two conditions, temperature and pH affect the ability of
amylase to hydrolyze (digest) starch.
Lugol’s iodine is used to detect starch which stains dark-blue/black in its presence. If starch is
digested by amylase to maltose, this color will disappear since maltose does not react in this way
with iodine. The color that remains will be that of iodine.
Exercise 1: Starch hydrolysis by the enzyme amylase
Procedure
41
1.
Obtain a spot plate that has many small depressions on its surface.
2.
Place a drop of iodine into each of the depressions. Each well will be used to detect
the presence of starch.
3.
Obtain a test tube and fill it with 10 ml of starch. This is the reaction tube.
4.
Add 1 ml of 1% amylase. Mix carefully by inversion, after covering the tubes with a
small piece of Parafilm®. Immediately remove 1 drop from the reaction tube and
place into one of the wells on the spot plate. A positive test for starch should be
observed.
5.
Remove a small sample from the reaction tube and test for starch at 2 minute
intervals. Continue this for a 10-minute period, and record the time at which no
starch is detected (the time at which all the starch is converted to maltose).
6.
Tabulate your observations making a note of the time interval and what you
observed.
Time (min)
0
2
4
6
8
10
Starch present? ( + or - )
If starch is still present even after 10 minutes of reaction time, can you detect a lighter color
when you add the sample to the drop of iodine? If so, why?
_______________________________________________________________________________
_______________________________________________________________________________
Exercise2: Effect of Temperature on Starch Hydrolysis
What effect do you predict temperature will have on the reaction of amylase with starch?
_______________________________________________________________________________
42
_______________________________________________________________________________
At which temperature do you think the reaction will proceed best? Why? (Hint: Where is
amylase found?)
_______________________________________________________________________________
_______________________________________________________________________________
Procedure
1.
Get 4 test tubes and label one each: ice; RT (room temperature); 40°C; boiling.
2.
Into each tube, pipette 10 ml of starch solution, and place each tube in a water bath
of appropriate temperature. Incubate the tubes for 5 minutes to allow the starch to
come to that temperature (to equilibrate).
3.
During the 5-minute incubation, prepare your spot plate by adding a drop of iodine
to each well.
4.
After the 5-minute incubation, add 1 ml of the 1% amylase solution. Mix carefully
by inversion, after covering the tubes with a small piece of Parafilm®. Remove the
Parafilm® and return the tubes to the water baths. (Do not mix the tube in the boiling
water bath!)
5.
At 2-minute intervals, remove 1 drop from each tube and test for the presence of
starch by dropping the solution into a well containing iodine.
6.
Continue testing for the presence of starch at 2-minute intervals, as described above,
until no starch is detected, that is, until the hydrolysis is complete, in each of the 4
reaction tubes. Use the following table to keep track of the results for each test by
placing a + or - to indicate the presence or absence of starch.
Temp. (°C)
2 min.
4 min.
6 min.
10 min.
12 min.
14 min.
16 min.
18 min.
4 (ice)
25 (RT)
40 (warm)
100 (boiling)
7.
From the above table, note the time needed for complete hydrolysis, and write the
43
times for each corresponding temperature in the table below.
Temp. (°C)
Time to complete
hydrolysis (min.)
4 (ice)
25 (RT)
40 (warm)
100 (boiling)
44
Exercise 3: Effect of pH on Starch Hydrolysis
What effect do you predict pH will have on the hydrolysis of starch by amylase?
_______________________________________________________________________________
_______________________________________________________________________________
At what pH do you think the reaction will proceed best? (Hint: What is the pH where
amylase is found?)
_______________________________________________________________________________
Procedure
1.
Get 3 test tubes and label one each: pH 4, pH 7, and pH 10.
2.
Pipette 5 ml of the appropriate pH buffer into each tube. Add 5 ml of the starch
solution to each tube, and mix by swirling.
3.
Add 0.5 ml of the amylase solution to each tube; mix by inversion. Take 1drop
from each tube and test for the presence of starch, as described above.
4.
Continue to test for starch every 2 minutes until the reaction is complete in each
tube, that is, until the iodine solution no longer changes color to darkblue/black. Use the following table to keep track of the results for each test by
placing a + or - to indicate the presence or absence of starch.
pH of Buffer
2 min.
4 min.
6 min.
10 min.
12 min.
14 min.
16 min.
18 min.
4
7
10
5.
Note the time it takes for the hydrolysis to reach completion at each pH from the
table above and fill in the table below.
pH of Buffer Time to complete
hydrolysis (min.)
4
7
45
10
Were your results what you had predicted before starting the experiment? Why or why not?
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
Exercise 4: To demonstrate that different cell types produce varying amounts of the
enzyme CATALASE.
During cellular metabolism, cells produce a by-product, hydrogen peroxide (H2O2) which
is toxic to cells. To get rid of the hydrogen peroxide, cells produce an enzyme called catalase
which breaks down the harmful hydrogen peroxide into the harmless water and oxygen.
Hydrogen peroxide =
H2 O2
=
water
H2 O
oxygen
O2
+
+
When hydrogen peroxide is added to living cells, this reaction takes place and the oxygen
released can be observed as bubbles leaving the tissue.
In this experiment you will investigate the varying amounts of catalase in different cell types.
Procedure
1.
Weigh out 1g of each of the tissues provided.
2.
Cut up the tissues and place each of the chopped tissues into a test tube. Use a spatula
or a glass rod to push all of the tissue to the bottom of the test tube. You need to use
all identical test tubes for this experiment.
3.
Place 1g of chopped potato into a test tube with about 10 ml of water and boil for
five minutes. Drain off the water.
What is the purpose of this test tube?
________________________________________________________________________
46
4.
Add 5 ml of hydrogen peroxide to each tube and mark the level of the hydrogen
peroxide immediately. Do one tube at a time so that you can mark the level of the
hydrogen peroxide as soon as you add it.
5.
Allow the tubes to stand for 5-7 minutes and then mark the height to which the foam
rises.
6.
While you are waiting you can confirm that the gas being produced is oxygen by doing
the test for oxygen gas. Place a glowing splint into the test tube. Describe what happens.
________________________________________________________________________
7.
Measure the height of the foam in mm and record your results in the table below.
Cell type
Height of foam (mm)
Boiled potato
47
Review Questions
1.
Consider the chemical reaction:
starch + water = maltose
a.
Specifically what type of chemical compound is starch? maltose?
starch _____________________
b.
maltose_____________________
What type of chemical reaction is represented by the equation above?
__________________________________________________________________
c.
In this reaction what is the substrate? Product?
substrate _____________________ product _____________________
2.
(a) At what temperature did the reaction proceed best? Why do you think this is
the ideal temperature for this enzyme?
____________________________________________________________________
____________________________________________________________________
(b) Explain why was there no breakdown of starch in the tubes placed at
(i) 100°C
____________________________________________________________________
____________________________________________________________________
48
(ii) 4°C?
____________________________________________________________________
____________________________________________________________________
3.
(a) At what pH did this enzyme work best?
_______________________________________________________________________
(b) Amylase is an enzyme produced in the human body. State 2 areas of the human
body where amylase is found.
_______________________________________________________________________
_______________________________________________________________________
(c) Name an enzyme in the human body that works best at acid pH.
_______________________________________________________________________
4.
What is the active site of an enzyme?
_______________________________________________________________________
_______________________________________________________________________
5.
From your results, which tissue type produced the most
catalase?_________________________
Which produce the least? _____________________
Explain why there was no bubbling in the tube with the boiled potato.
_______________________________________________________________________
_______________________________________________________________________
In which organelle of the cell would you expect to find the enzyme catalase?
____________________________________________
49
50
EXERCISE 6
Osmosis and Diffusion
LEARNING OBJECTIVES




Investigate the processes of diffusion and osmosis and understand their
importance to living cells.
Determine experimentally how temperature and concentration affect the rate
of diffusion.
Determine experimentally the tonicity of unknown solutions;
Demonstrate the role of selectively permeable membranes in diffusion.
Answer these questions before you come to lab:
1. Define the following terms:
Passive transport
Active transport
Selectively permeable
Osmosis
Simple diffusion
Equilibrium
2. If a solution outside of a cell contains a higher concentration of a solute (e.g.
glucose or sodium chloride) than the cytoplasm inside the cell, the solutions is
said to be ____________________. Water will ____________ the cell.
3. If a solution outside of a cell contains a lower concentration of a solute (e.g.
glucose or sodium chloride) than the cytoplasm inside the cell, the solution is said
to be __________________. Water will ____________ the cell.
4. If a solution outside of a cell contains the same concentration of a solute (e.g.
glucose or sodium chloride) than the cytoplasm inside the cell, the solution is said
to be _________________. Water will ___________________________ the cell.
51
INTRODUCTION
Water is an essential requirement of all cells. For example, a plant that is not
watered enough starts to wilt. In terms of osmosis and diffusion, there is not
enough water within the cells for them to retain their shape and strength, so the
plant starts to die. This is just one example of the importance of water and how
water movement is necessary for the maintenance of cell structure and function.
All cells have membranes that surround them. These membranes are said to be
selectively permeable, which means that the membrane allows molecules
through only if they are small enough to pass through the membrane.
This exercise demonstrates the process of osmosis in which water molecules
move from a high concentration of water to lower concentration of water and the
effect of temperature on this process.
Exercise 1: Effect if temperature on osmos i s
Procedure
1.
Prepare an artificial cell by taking a small piece of the pre-wetted dialysis
tubing and tying one end to make a tube. Dialysis tubing is a selectively
permeable membrane, much like that of the cell. It will allow small molecules
such as water through pores in its structure.
2.
Place 5 ml of 60% molasses in the tube.
3.
Carefully tie the other end of the tube to seal it.
4.
Rinse the cell briefly under tap water to clean it and gently dry.
5.
Use the electronic balance to weigh your cell (Cell 1). Record your results in
the table below to 3 decimal places. (Initial weight).
6.
Repeat steps 1-5 to make another cell with 60% molasses (Cell 2).
7.
Get two 600ml beakers. Half fill one of them with tap water, leave one on
your table and place Cell 1 in it.
8.
Half fill the other beaker with water taken from the 40°C water bath. Place
this beaker into the water bath with Cell 2 in it.
Note the time you put the cells in the water and record the temperature of
the water in each case. You will leave them for 1 hour.
52
What do you think will happen to your cells? Will they shrink, swell or stay the
same? Explain your answer.
____________________________________________________________________
__________________________________________________________________
This is your hypothesis.
Table 1.
After 1 hour, remove the cells and gently blot them dry with paper
towels and weigh them again. (Final weight).
Table 1.
Cell 1 (60% molasses)
(22°C room temp)
Cell 2 (60% molasses)
(40°C water bath)
Initial weight (g)
Final weight (g)
Weight change (g)
(Final-Initial weight)
What has happened to the weights of your cells?
________________________________________________________________________
Why do you think this has occurred?
________________________________________________________________________
To check whether your hypothesis was correct, compare your results with those of the
other lab groups.
Exercise 2: Effect of concentration on osmosis
What would be the result using different concentrations of molasses solution in the cells?
________________________________________________________________________
Check your hypothesis by making another cell.
1.
Place 5ml of 80% molasses into the cell, rinse, pat dry and weigh. (Initial
weight).
2.
Place the cell in a 600ml beaker half filled with tap water on your table.
53
3.
After 1 hour remove the cell pat dry and weigh again. (Final weight).
Table 2.
Cell 1 (60% molasses)
Cell 3 (80% molasses)
Initial weight (g)
Final weight (g)
Weight change (g)
(Final-Initial weight)
What is the difference in weight change between cell 1 and 3? ___________ g
If there were differences, what would account for those differences?
____________________________________________________________________
____________________________________________________________________
Why was it important to leave the cells in the water for exactly the same amount of time?
____________________________________________________________________
____________________________________________________________________
54
Exercise 3: Plant Cell Experiment
In this experiment you will investigate the effect of different concentrations of
sucrose solution on potato cells. The solutions are 0. 1M, 0.2M, 0.4M, 0.8M and
distilled water. (M means molar and is one way of expressing the concentration
of a solution. 1M is the molecular weight of sucrose in 1 liter of water. The concentration
increases from 0.IM to 0.8M). The solutions are labeled V, W, X, Y, and Z. We
will first weigh the potato tissue, place them in the solution for some time and then weigh
them again. From your results you should be able to identify each of the solutions
based what happens to your potato cylinders when they are left in the solutions.
The solutions may be hypotonic, hypertonic or isotonic compared to your potato
cells.
What would you expect to happen to the size of the cells (and hence the weight of
the cylinder) if the solution is
hypertonic
___________________________________________________________________
hypotonic
___________________________________________________________________
isotonic
_____________________________________________________________________
Procedure
1.
Make a potato cylinder by pushing a cork borer all the way through the
potato. DO NOT PUT THE BORER THROUGH A SPOT THAT
ALREADY HAS A HOLE. Release the cylinder from the cork borer by
pushing a pencil or similar object through the hole in the borer.
2.
Using a razor blade, cut both ends of the potato cylinder so that no potato peel
is present.
3.
Make 4 more cylinders in the same way.
4.
Use the electronic balance to weigh each cylinder (label them V-Z) and record
the weight in the table below. This is the initial (or starting) weight of the
cylinders.
Record your potato cylinder results here.
55
56
Table 3.
Cylinder in Cylinder in Cylinder in Cylinder in Cylinder in
(solution V) (solution W) (solution X) (solution Y) (solution Z)
Initial weight (g)
Final weight (g)
Final-initial
weight (g) + or -
5.
Place each cylinder in a different test tube and pour in enough of each of
the solutions provided to ensure the cylinders are fully covered. Match the
cylinders with the solutions V, W, X, Y, and Z as shown in the table below.
6.
Let the cylinder sit undisturbed for at least 90 minutes.
7.
After 90 minutes, blot the potato cylinders GENTLY on a paper towel and
record the weights in the table above.
8.
Calculate the weight change of your cylinders, indicating if the weight
increased (+) or decreased (-).
9.
Now compare your results with the class results by writing the weight change
for each cylinder on the board.
10.
Record the average of the class results in the table below.
Record the Class Results here.
Table 4.
V
W
X
Y
Z
Average weight
change (g) (+ or -)
Exercise 4: To demonstrate selective permeability.
A selectively permeable membrane will allow some molecules to pass through and not
others. This may be based on the size of the molecules. Dialysis tubing is a selectively
permeable membrane.
Glucose and starch are both carbohydrates. What type of carbohydrate is
Glucose? _______________________________
Starch? _________________________________
57
Procedure
1.
Prepare an artificial cell as you did before in Exercise 1.
2.
Fill the cell to about 5ml with the glucose /starch mixture.
3.
Rinse the cell well and place in a beaker of distilled water and leave for 45
minutes.
4.
After 45 minutes, get a clean test tube and measure out 2 ml of the water in
which the cell was sitting and place into the tube.
5.
Add 2 ml of Benedict's solution.
Benedict’s solution is used to test for
____________________________________
6.
7.
Place the tube in the boiling water bath for about 5 minutes and observe
any color change.
Place a drop of iodine in a well of the depression plate. Add a drop of the
taken from around the cell.
Iodine tests for ___________________________
8.
Record your results in the table below.
Table 5.
Liquid from beaker tested
with
Benedict’s solution
Iodine solution
Color
Substance present
Which substance was present in the water?
58
water
__________________________________
Which substance was not present in the water?
_______________________________
Explain why this substance was present while the other was absent from the water.
____________________________________________________________________
____________________________________________________________________
59
Exercise 5: Observing Plasmolysis.
Procedure
1.
Take a leaf of Elodea and place it on a slide with a drop of water and put on
a cover slip.
2.
Using the 40X objective, observe the cells under the microscope and draw 4
of the cells that you see.
3.
Make a new slide with a fresh leaf but use a drop of solution A.
4.
Draw 4 cells from this slide.
60
What difference do you observe between the cells in the 2 slides?
____________________________________________________________________
____________________________________________________________________
Describe what you observe happening in the cells in solution A.
____________________________________________________________________
____________________________________________________________________
____________________________________________________________________
What kind of solution is solution A compared to the cytoplasm of the cells? Explain
your answer.
____________________________________________________________________
____________________________________________________________________
61
Review Questions
1.
Explain fully why all the cells placed in water gained weight.
____________________________________________________________________
____________________________________________________________________
____________________________________________________________________
2.
Copy your results for cells 1 and 2 (Table 1) in the table below.
Cell 1 (60% molasses)
(22°C room temp)
Cell 2 (60% molasses)
(40°C water bath)
Initial weight (g)
Final weight (g)
Weight change (g)
(Final-Initial weight)
Explain why the cell placed in 40°C gained more weight in the time.
____________________________________________________________________
____________________________________________________________________
____________________________________________________________________
3.
Copy your results for cells 1 and 3 (Table 2) in the table below.
Cell 1 (60% molasses)
Cell 3 (80% molasses)
Initial weight (g)
Final weight (g)
Weight change (g)
(Final-Initial weight)
a.
What is meant by the term 'concentration gradient'?
____________________________________________________________________
b.
Explain why the cell with 80% molasses gained more weight in the
time.
____________________________________________________________________
62
4.
In the table below, copy the weight change in your potato cylinders (Table 3).
Cylinder 1 Cylinder 2
Cylinder 3 Cylinder 4 Cylinder 5
(solution V) (solution W) (solution X) (solution Y) (solution Z)
Initial weight (g)
Final weight (g)
Final-initial
weight (g) (+ or -)
Keeping in mind that the solutions may be either, hypotonic, isotonic or hypertonic to
the potato cells, explain the weight change in each of your cylinders.
In which of the solutions did the potato cylinders gain weight?
____________________________________________________________________
Explain why they gained weight.
____________________________________________________________________
____________________________________________________________________
In which of the solutions did they lose weight?
____________________________________________________________________
Explain why they lost weight.
____________________________________________________________________
____________________________________________________________________
What would you say about a solution in which the cylinder neither gained nor lost
weight?
Explain your answer.
____________________________________________________________________
____________________________________________________________________
5.
Record the results of the average weight change in potato cylinders placed in
the 5 different sucrose solutions, in the table below. (Class results Table 4).
63
The concentrations of the five solutions used were: 0.1M, 0.2M, 0.4M, 0.8M,
distilled water.
V
W
X
Y
Z
Average weight
change (g) (+ or -)
Which solution was water? Explain why you think so.
____________________________________________________________________
____________________________________________________________________
Which solution is 0.8M sucrose? Explain why you think so.
____________________________________________________________________
____________________________________________________________________
64
EXERCISE 7
Cellular Respiration
Learning objectives
 Observe the process of cellular respiration in yeasts
 Determine the effect of different variables on cellular respiration in yeast
 Illustrate how different organisms can affect the level of carbon dioxide in the
atmosphere
 Deduce that oxygen is used by germinating seeds
 Measure heat released as a by- product of cellular respiration
INTRODUCTION
Energy is required by all living organisms for metabolism. Where does that energy come from?
The process of cellular respiration involves the breakdown of complex organic molecules. By
breaking bonds in these molecules, energy is released in the form of adenosine triphosphate
(ATP). The ATP can be used to drive a number of cellular metabolic reactions in an organism.
The following chemical reaction illustrates the overall reaction that occurs in respiration.
C6H12O6 + 6O2
glucose
oxygen
6CO2 + 6H2O + ATP + Heat
carbon water
dioxide
The equation above summarizes the very complex process of cellular respiration which involves
a series of many biochemical reactions in a metabolic pathway. These reactions have been
organized into three stages: glycolysis, the Krebs Cycles (citric acid cycle), and the electron
transport chain. Some organisms can also generate ATP by the process of fermentation. The
processes of cellular respiration and fermentation are illustrated in the diagram below;
65
Answer the following questions before you come to lab:
1.
What is the initial substrate for cellular respiration? ---------------------------2.
How may ATP molecules are produced during glycolysis? Krebs’ cycle? Electron
transport chain?
Glycolysis
Krebs’ cycle
Electron transport chain
Total
3.
What is the final electron acceptor in aerobic respiration?
4.
Why is heat released during cellular respiration when it cannot be used by cells?
5.
If oxygen is not available this type of respiration is called
6.
Name 2 molecules that are used as the final electron acceptor if oxygen is not
available. State the products formed in each case.
66
Final electron acceptors in
fermentation
Products
7.
How may ATP molecules are produced from fermentation? _________________
8.
Name the three different molecules that make up a molecule of ATP.
In the following exercises, you will measure both examine and fermentation.
FERMENTATION
Exercise 1: Fermentation in Yeast
One type of anaerobic respiration most common to us involves the use of yeast in the production
of bread and alcoholic beverages e.g. beer and wine. The yeasts use sugar present in the extract
(e.g. grape juice) as a substrate and produce CO2 and alcohol as byproducts. This process is
known as fermentation. It is anaerobic since no oxygen is involved. We can measure the amount
of CO2 produced by the yeasts as an indication of how efficiently they are able to carry out
fermentation.
1.
Obtain 4 fermentation tubes and fill them according to the table below. Your instructor
will demonstrate the proper way to fill the tubes so that no air bubbles are present in the
neck of the tubes.
Table 1 – Solution amounts of fermentation experiment.
Tube #
1
2
3
4
2.
3.
3M sodium
pyruvate
0.1 M NaF
(poison)
5.0 ml
5.0 ml
5% glucose
water
2.5 ml
2.5 ml
2.5 ml
5.0 ml
7.5 ml
Finish filling the tubes with 25 ml of the yeast solution provided.
Incubate the tubes at 40°C for 45 minutes.
67
4.
After 45 minutes, use a ruler to measure the height of the bubble (CO2) in each tube, and
write your results in Table 2.
Which tube would you expect to produce the most CO2? The least? Explain your answers.
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
Table 2 – Size of CO2 bubble.
Tube #
Height of CO2
bubble (mm)
1
2
3
4
Exercise 2: Effect of Temperature on Fermentation
1.
2.
3.
Obtain 2 more fermentation tubes (tubes 5 and 6).
Prepare them exactly as Tube 1. Place 2.5 ml glucose and 5.0 ml water into each tube,
and fill with yeast solution.
Put tube 5 at room temperature (20°C) and tube 6 in the refrigerator (4°C)
Tube 1 (40°C) from the previous exercise is included in this experiment
Measure the size of the bubble after 40 minutes and record your results in Table 3.
68
Table 3 – Size of CO2 bubble.
Tube #
Temperature
Height of CO2
bubble (mm)
1
5
6
Which tube would you expect to produce the most CO2? The least? Explain your answers.
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
Exercise 3: Release of carbon dioxide during anaerobic respiration
In this experiment you are going to use a yeast mixture. The yeast mixture was prepared by first
boiling a sugar solution (to remove all dissolved air) and then adding the yeast after it was
cooled.
Procedure
1.
2.
3.
Use the apparatus provided to setup the experiment as shown in the diagram below.
Half fill the large test tube with the yeast mixture.
Pour in oil just to cover the surface of the mixture.
69
What is the purpose of the oil layer?
________________________________________________________________________
4.
Half fill the other tube with phenol red.
What is the reason for using phenol red?
________________________________________________________________________
5.
Place the stopper with the delivery tube tightly (BE CRAEFUL!) on the tube with the
yeast.
6.
Arrange both tubes on the test tube rack so that the end of the delivery tube is submerged
in the phenol red.
7.
Set up an identical experiment but use killed yeast instead.
What is the purpose of this duplicate experiment? _______________________________
Why was oil added to the surface of the yeast?
________________________________________________________________________
________________________________________________________________________
70
What is the color of phenol red in a neutral solution?
________________________________________________________________________
________________________________________________________________________
Explain why the color changed.
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
Exercise 4: How organisms affect the amount of carbon dioxide in the atmosphere.
Procedure
1.
Label four large test tubes 1-4.
2.
Place 5 ml phenol red into each tube.
3.
Place the following into the tubes and stopper tightly (see diagram).
Tube
1
2
3
4
Organism(s)
a green leaf
some small animals in a piece of gauze
a green leaf and animals in a piece of gauze
no organisms
4.
Place the tubes in a rack on the bench and observe periodically for about an hour.
5.
Gently shake the tubes every 10 minutes and observe the time taken for any color change.
Record your results in the table below.
Time
(mins)
Start
10
20
30
40
50
60
Color
Tube 1
Tube 2
71
Tube 3
Tube 4
Which tube changed first? Explain why this tube changed first.
__________________________________________________________________
__________________________________________________________________
What color change took place in tube 1? Explain.
__________________________________________________________________
__________________________________________________________________
Describe what was happening in tube 3.
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
72
Exercise 5: Use of oxygen during respiration by germinating seeds.
Soda lime is a chemical substance that absorbs carbon dioxide. Any carbon dioxide produced by
the organisms is removed by the soda lime.
Observe the experiment, which has been set up.
When the organisms use up oxygen, what will happen to the pressure in the flask?
________________________________________________________________________
Describe what you observe taking place in each of the glass tubing.
________________________________________________________________________
________________________________________________________________________
What is the function of the potassium hydroxide (soda lime) pellets?
________________________________________________________________________
Explain why the level of the colored water rose in one glass tubing and not in the other.
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
73
Exercise 6: Release of heat by germinating seeds.
The experiment was set up as follows:
1.
Moist cotton wool was placed at the bottom of a thermos flask and the flask was filled
with germinating seeds.
2.
A thermometer was inserted and the flask and cotton wool used as a stopper.
3.
A second flask was set up in the same way with non-germinating seeds.
4.
Note the temperature in each flask:
Flask with live seeds _______________________
Flask with dead seeds ______________________
Why were thermos flasks used?
________________________________________________________________________
Why was the flask with non-germinating seeds included in the experiment?
_______________________________________________________________________
Since respiration releases heat energy, what type of biochemical process is it?
___________________________________
74
Review Questions
Exercise 1: Anaerobic Respiration
Tube #
Contents of Tube
Height of CO2
bubble (mm)
1
2
3
4
1.
What was the function of Tube 1 and Tube 4?
________________________________________________________________________
2.
Although Tube 4 contained no glucose a bubble was still produced by the yeast. Where
did they get the sugar for respiration?
________________________________________________________________________
________________________________________________________________________
3.
NaF is a poison. Which substances, essential for metabolic processes could be inhibited
by the NaF? Explain.
________________________________________________________________________
________________________________________________________________________
4.
(a)
Yeast carry out alcohol fermentation. How is alcohol fermentation different from
lactic acid fermentation?
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
75
(b)
What effect did the addition of pyruvate have on the reaction in tube 3? Explain.
__________________________________________________________________
Exercise 2: Effect of temperature on respiration
Tube #
Temperature
Height of CO2
bubble (mm)
1
5
6
5.
Which of the fermentation tubes (1, 5, or 6) produced the greatest amount of CO2?
Explain your results fully.
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
76
EXERCISE 8
Photosynthesis
LEARNING OBJECTIVES:
 Understand the components of the equation for photosynthesis.
 Observe evidence of plants taking up carbon dioxide.
 Observe the relationship between the presence of pigments for
photosynthesis and the presence of carbohydrate product (starch).
 Observe evidence of plants producing oxygen.
 Demonstrate that light is necessary for photosynthesis.
 Observe the presence of stomata in the epidermis of plant leaves.
Answer these questions before you come to lab:
1. Define:
autotrophic_____________________________________________
Heterotrophic___________________________________________
2. During photosynthesis plants convert ___________ energy to _____________
energy in the form of ______________.
3. List the factors necessary for photosynthesis.
_______________________________________________________________
4. Which of these factor(s) are used in the light reactions?
_______________________________________________________________
5. Which are used in the light-independent reactions (Calvin cycle)?
_______________________________________________________________
6. What are the products of the light reactions?
____________________________________________________________
7. What are they used for in the Calvin cycle?
_____________________________________________________________
_______________________________________________________________
77
8. What are the products of the Calvin cycle?
_______________________________________________________________
9. Write the general equation for the process of photosynthesis.
_____________________________________________________________
EXERCISE 1: To show that carbon dioxide is taken up during
photosynthesis.
Introduction
Plants require CO2 to produce glucose during the light-independent reactions (also
called the ____________________) of photosynthesis. Therefore if CO 2 disappears,
there is evidence that photosynthesis is occurring. A pH indicator solution can be
used to detect the uptake of CO2 by a plant. An indicator is a molecule that changes
color depending on pH. Today you will be using phenol red solution. Phenol red
solution turns yellow in acidic solutions (pH <7.0) and is red to neutral to basic
solutions (pH >7.0).
In order to see this color change take place, you will breathe CO2 from your lungs
into a solution of phenol red. The phenol red solution will begin basic (red) and
become acidic (yellow) as you add CO2. This is due to the following chemical
reaction between water and carbon dioxide.
H2 O +
water
CO2
H2CO3
carbon
dioxide
carbonic
acid
If a plant is added to an acidic solution it can “fix” (or take up) the carbon dioxide.
Removing CO2 from the solution raises the pH (becomes more basic). This causes a
yellow solution to turn red.
Procedure
1.
In a beaker, mix 50 ml of water with 10 drops of phenol red indicator.
2.
Mark two test tubes with your initials. Fill one tube half-full with the phenol
red-water mixture. You will have phenol red-water mixture remaining in the
beaker.
78
3.
Using a straw, gently blow into the beaker, being careful to avoid splashing.
Stop blowing as soon as your solution turns yellow. Otherwise, the experiment
will take longer because of the additional carbonic acid formed.
4.
Fill the second labeled test tube half-full with this yellow solution (phenol redwater rich in C02 ).
5.
Add t wo pi eces ( about 3 cm each) of Elodea stem (with leaves) to each test
tube.
6.
Pour off any excess phenol red-water solution so that the solution just covers
the Elodea.
7.
Place both test tubes under the bright light for 30-60 minutes (this will
insure that the plant has adequate supplies of ATP and NADPH necessary
for the light-dependent reactions).
8.
Observe the solutions every 10 minutes and record the time and color
changes you observe in Table 1.
Table 1. Record of time and solution color
Time
Color
Has the color in either test tube changed? If so, why?
____________________________________________________________________
____________________________________________________________________
____________________________________________________________________
79
EXERCISE 2: To demonstrate that chlorophyll is required for
photosynthesis.
Explain what chlorophyll is used for during photosynthesis.
____________________________________________________________________
____________________________________________________________________
Procedure
A variegated leaf is one is which pigments are not evenly distributed.
1.
Sketch this leaf in the "before" section of Figure 1, making sure to indicate
the location of the pigments (the parts that are white and those that are green)
Before
After
Figure 1. Student sketch of leaf before and after staining
2.
Bring half a beaker of water to boil.
3.
Boil the leaf in water for 1 minute. This kills the leaf.
4.
Carefully remove the leaf from the water.
80
5.
Half fill a test tube with 95% ethanol, and place the killed leaf in it.
6.
Place the test tube in the beaker of boiling water and boil for about or until all
of the pigment is removed.
7.
Place the leaf into cool tap water for 30 seconds or until it becomes soft. The
alcohol make it hard)
8.
Carefully spread the leaf out on a Petri dish and stain it with iodine. Wait 5
minutes and then make a sketch of the stained leaf in the ‘ aft e r’ section of
Figure 1. Indicate the areas that are black.
How is the presence of starch related to the process of photosynthesis?
____________________________________________________________________
____________________________________________________________________
____________________________________________________________________
Why would dark brown/black staining be absent if the portion of the leaf was
originally white?
____________________________________________________________________
____________________________________________________________________
____________________________________________________________________
Describe how carbon dioxide is used in photosynthesis.
____________________________________________________________________
____________________________________________________________________
____________________________________________________________________
____________________________________________________________________
81
EXERCISE 3. To show that light is necessary for photosynthesis.
Procedure
1.
Obtain a leaf from a plant kept in the light and one kept in the dark.
2.
Using two separate test tubes and the method described in Exercise 2, test
both leaves for starch.
What does boiling the leaf in water do? In alcohol?
____________________________________________________________________
____________________________________________________________________
____________________________________________________________________
Was there starch formation in the leaf from the plant kept in the dark? If so, was
this what you expected?
____________________________________________________________________
____________________________________________________________________
____________________________________________________________________
Why do plants store starch?
____________________________________________________________________
____________________________________________________________________
82
EXERCISE 4. To demonstrate that oxygen is produced during
photoysnthesis.
During the light-dependent reaction of photosynthesis, water is split to produce the
hydrogen needed for the reduction of carbon dioxide during the light-independent
reaction (or Calvin cycle). This splitting of water also produces oxygen, which is
released as a gas (O2), a by-product. The production of oxygen can be observed using
the aquatic plant, Elodea.
This demonstration has been set up so that molecules of oxygen produced during
photosynthesis are trapped in a test tube attached to the narrow end of a funnel.
Several fresh sprouts of aquatic plant are placed under the funnel and the entire
system is submerged in w a t e r t a k i n g c a r e t o e n s u r e t h a t the oxygen produced
will be trapped in the test tube rather than escaping into the air. Since tap water does
not contain much carbon dioxide, sodium bicarbonate is added to release carbon dioxide
into the water.
Observe the demonstration periodically during your lab period to observe formation
of oxygen as the level of water in the test tube is displaced. You may also see that
oxygen is being produced by observing the bubbles as they travel from the aquatic
plant to the test tube.
83
What would happen if this system was only allowed green light? Explain your answer.
____________________________________________________________________
____________________________________________________________________
Why is the system submerged in a solution of sodium bicarbonate rather than pure
water?
____________________________________________________________________
____________________________________________________________________
Exercise 5: Observing stomata on the epidermis of the leaf
Procedure
1. Paint a small area about the size of a dime with clear nail polish on the
underside of the leaf.
2. Allow the nail polish to dry completely.
3. Tape a piece of clear tape onto the dried nail polish.
4. Peel the nail polish (BE GENTLE!) by pulling on the tape.
5. Gently press the tape with your leaf impression onto a clean slide.
6. Examine under the microscope 40X.
7. Draw a few of the stomata you observe in the space below.
84
Lab Report
Exercise 1
1.
What is phenol red?
____________________________________________________________________
2.
What was the purpose of blowing into the water solution of phenol red?
____________________________________________________________________
3.
What caused the color to change to yellow?
____________________________________________________________________
4.
Explain why the color changed from yellow back to pink after leaving the
Elodea in it for an hour.
____________________________________________________________________
5.
What was the purpose of the other tube (without the plant)?
____________________________________________________________________
____________________________________________________________________
Exercises 2 and 3
6.
What does boiling the leaf in water do?
____________________________________________________________________
7.
Why is the leaf then boiled in alcohol?
____________________________________________________________________
8.
Which area of the variegated leaf contained chlorophyll?
____________________________________________________________________
85
9.
What does a blue-black color with iodine indicate?
___________________________________________________________________
10.
Which areas of the leaf stained blue-black?
____________________________________________________________________
11.
Explain why only those areas stained blue-black?
____________________________________________________________________
____________________________________________________________________
12.
Was there any starch in the leaf that had been left in the dark? Explain your
answer.
____________________________________________________________________
____________________________________________________________________
Exercise 4
13.
Why was the plant submerged in a solution of sodium bicarbonate instead of
pure water?
____________________________________________________________________
14.
What would have happened if green light were used instead? Explain your
answer.
____________________________________________________________________
____________________________________________________________________
____________________________________________________________________
86
EXERCISE 9
Cell Division
LEARNING OBJECTIVES





Describe the stages of interphase
Model and draw the stages of mitosis and meiosis
Compare and contrast mitosis and meiosis
Identify the stages of mitosis in plant and animal cells
Explain the importance of synapsis and crossing over
INTRODUCTION
Cell division is important to living organisms for reproduction, growth, repair of injured tissue,
and replacement of dead cells. Prokaryotic organisms, such as bacteria, have a single
chromosome and simply replicate that chromosome and split into two by the process of binary
fission. Eukaryotic organisms, on the other hand, have multiple paired chromosomes. Their cells
divide by a process known as the cell cycle, during which the nucleus divides. This division of
the nucleus is called mitosis when they divide asexually and meiosis when the cell division
produces gametes. Because they have multiple chromosomes, eukaryotic cells employ the use of
the spindle to organize the chromosomes and ensure that they are distributed correctly to the
daughter cells.
Answer the following questions before you come to lab:
The diagram below is of the cell cycle. Label each part of the cycle and describe (next to the
label) what happens during that stage.
87
In which stage of the cell cycle does the cell spend most of its time?_______________________
What is the spindle made of?______________________________________
What do the following terms mean?
Cytokinesis________________________________________________________________
Centromere________________________________________________________________
Chromatid_________________________________________________________________
Homologous chromosomes___________________________________________________
A duplicated chromosome is shown below. Label it.
Figure 2
Exercise 1: Mitosis/Meiosis Video
Pay close attention to the information in the video, since it will be followed by a video quiz.
Exercise 2: Modeling the stages of Mitosis
1.
Use the playdoh to model two pairs of homologous chromosomes, each consisting of two
chromatids. Make one long pair (about 6 cm long) of one color e.g. blue and then make
its homologous pair of a different color e.g. red. Since they are homologous they must be
of the same length.
Also make one short pair (about 3 cm), also using different colors for each
homologue.
2.
Model the stages of mitosis using the chromosomes you have made and record the stages
using colored pencils in the spaces provided on the next page.
88
Exercise 2: Modeling stages of Mitosis
Interphase
Prophase
Metaphase
Anaphase
Telophase/Cytokinesis
89
Exercise 3: Mitosis in animal cells (whitefish blastula) mitosis.
A blastula is the ball of cells produced as an embryo divides. After an egg (haploid) and sperm
(haploid) fuse during fertilization, the resulting cell is called the zygote (diploid). This cell
divides by mitosis and the resulting cells continue dividing repeatedly to produce the ball of cells
called the blastula.
In this exercise, you will examine slides of the whitefish blastula to observe the cell cycle of
animal cells.
1.
Obtain a slide labeled “whitefish blastula.” Examine the slide under scanning power
(4X). You will note round circles. Each circle contains numerous sections of blastula.
Each blastula section has many cells, which maybe in various stages of mitosis or in
interphase.
2.
Select a section and switch to low power and then high power for detailed observation.
(Follow the appropriate rules for using the microscope that you microscopy learned in
previously).
3.
Work in groups and find the following stages of the animal cell’s life cycle. You may
refer to your text book and the diagram on the below.
Identify all the stages of the cell cycle in cells of the prepared slide of whitefish blastula and
draw them in the spaces provided on the next page.





Interphase
Prophase
Metaphase
Anaphase
Telophase/cytokinesis
Figure 3 Mitosis in whitefish blastula
Exercise 3: Mitosis in animal cells (whitefish blastula) mitosis.
90
Interphase
Prophase
Metaphase
Anaphase
Telophase/Cytokinesis
Exercise 4: Mitosis in plant cells (onion root tip).
91
Mitotic divisions in plant cells take place only in specialized regions called meristems.
Meristems are present in the root tips and shoot tips of the plant and are regions of active growth
that result in the elongation of tips in stems and roots. There is also a meristem in the trunk of the
plant and mitotic division of cells in this region result in expansion of girth of plants. Cell
division continuously occurs in these meristem regions of plants; there are no comparable
regions in animals. In this exercise, you will examine prepared slides of the root tip meristem of
Allium (onion).
1.
Obtain a prepared slide of a longitudinal section of Allium (onion) root tip.
2.
Focus first with scanning power to get an overall view of the root tip (see diagram
below). Examine the region behind the root cap, which is the apical meristem of the root
tip.
3.
Switch to high power and observe the stained chromosomes within the nuclei of
the cells in this region, and the cells undergoing mitosis (where no nucleus in present).
4.
Work in groups and find the following stages of the animal cell’s life cycle. You may
refer to your text book and the diagram on the below.
Identify all the stages of the cell cycle in cells of the prepared slide of onion root tip and
draw them in the spaces provided on the next page. Also note any similarities and
differences between plant and animal cell mitosis.
Exercise 4: Mitosis in plant cells (onion root tip).
92
Interphase
Prophase
Metaphase
Anaphase
Telophase/Cytokinesis
INTRODUCTION TO MEIOSIS
93
Answer these questions before you come to lab:
What do the following terms mean?
Tetrad__________________________________________________________________
Synapsis________________________________________________________________
Gonads _________________________________________________________________
Crossing over____________________________________________________________
Gamete_________________________________________________________________
How are the daughter cells produced from meiosis different from those produced from mitosis?
___________________________________________________________________________
___________________________________________________________________________
Meiosis is a form of cell division that occurs in the gonads, the ovaries and testes, of animals.
The purpose of meiosis is production of gametes which are haploid do that fertilization will
restore the diploid number of chromosomes. This process is called gametogenesis. Meiosis also
occurs in plants. In flowering plants this takes place in the anther and ovary of the flower.
Meiosis occurs in two cycles. Meiosis I consists of prophase I, metaphase I, anaphase I, and
telophase I, accompanied by cytokinesis. The second cycle consists of prophase II, metaphase II,
anaphase II, and telophase II, also accompanied by cytokinesis.
The chromosomes in diploid somatic (body) cells of eukaryotes exist in pairs called homologous
chromosomes. One chromosome of each pair comes from the father, and the other comes from
the mother. Homologous pairs contain similar, but not always identical, generic material for a
series of traits. They carry the same genes at specific loci, but they are often in alternate forms
called alleles. Somatic cells are diploid (2n), containing two sets of homologs in the same
nucleus. Following meiosis, all four daughter cells contain only one of each of the paired
homologs and are haploid (n).
Prophase I is unique in that homologous chromosomes pair with each other and intertwine as a
tetrad (see your textbook as a reference). This pairing of homologous chromosomes is called
synapsis. At this time, genetic material may be exchanged between non-sister chromatids during
a process called crossing over, in a form of genetic recombination. This process does not occur
during mitosis. Generally, each pair of homologues has at least one cross over.
94
Exercise 5: Modeling the stages of meiosis
1.
Use the playdoh to model two pairs of homologous chromosomes, each consisting of two
chromatids, as you did in Exercise 2.
2.
Model the stages of meiosis using the chromosomes you have made. Simulate one cross
over event between the long pair and one cross over event between the short pair.
3.
Record the stages using colored pencils in the spaces provided on the next page.
You may refer to the diagram on the following page.
95
Figure 4. Meiosis
96
Exercise 5: Modeling the stages of meiosis 1
Interphase
Prophase 1
Metaphase 1
Anaphase 1
Telophase 1
Cytokinesis 1
97
Exercise 5: Modeling the stages of meiosis II
Prophase II
Prophase II
Metaphase II
Metaphase II
Anaphase II
Anaphase II
Telophase II/Cytokinesis
Telophase II/Cytokinesis
98
EXERCISE 10
Genetics
LEARNING OBJECTIVES






Explain the genetic concepts of dominance and recessiveness.
Efficiently use of the Punnett square
Determine the outcome of monohybrid and dihybrid crosses.
Calculate expected phenotypic and genotypic ratios given the genotype of two parents.
Recognize that some human characteristics are inherited in a simple Mendelian fashion
and others are not.
Determine the outcome of genetic crosses involving the following principles: incomplete
dominance/co-dominance, multiple alleles, sex linkage
INTRODUCTION
Genetics is the science of heredity, which explains how characteristics are passed from parents to
their offspring. Much of our early understanding of genetics was due to the experiments of
Gregor Mendel done in the late 19th century. Mendel was able to discover some of basic
generalizations of the laws of inheritance from experiments on pea plants. These principles can
be applied to may sexually reproducing organisms. However, genetics is a very complex science
and while some of these generalizations apply to the inheritance of some human characteristics,
many human characteristics are passed on using genetic mechanisms that were not evident to
Mendel. In this lab, we will look at Mendelian genetics and also some ways in which a few
human characteristics are inherited.
Before you come to lab, make sure you know the definitions of the following terms.
Homologous
chromosomes
Gene
Allele
Homozygous
Heterozygous
Dominant
99
Recessive
Genotype
Phenotype
Monohybrid
Dihybrid
Incomplete
dominance
Codominance
Multiple alleles
Sex linkage
The Punnett Square
In order to understand how alleles are passed on from parent to offspring, a Punnett square is
often used. A Punnett square shows the possible combination of alleles that can result when male
and female gametes are crossed. The first part of this lab will give you practice with both
monohybrid and dihybird crosses.
In order to complete a Punnett square, the alleles from one parent are listed on the top of the
Punnett square, and the alleles from the other parent are listed along the side.
It does not matter which parent is listed along the top, and which is listed along the side.
SIMPLE DOMINANCE
Monohybrid Crosses
Exercise 1
With simple dominance, alleles that completely mask the alternate form of the gene are said to
be dominant. In other words, dominant alleles are fully expressed whenever they are present.
Dominant individuals could have either an AA genotype (homozygous dominant) or an
Aa(heterozygous). The recessive allele “a” would be hidden whenever it was combined with
100
“A”. Thus, recessive phenotypes will only show up when individuals are homozygous recessive
(aa).
In onion sweet taste is dominant over bitter taste. Using the letter T, t, for taste, complete the
following crosses, and fill in the phenotype ratios of the offspring.
1.
Homozygous Dominant X Homozygous Recessive
Phenotype Ratio of Offspring
______________________
2.
Heterozygous X Homozygous Recessive
Phenotype Ratio of Offspring
______________________
3.
Homozygous Recessive X Homozygous Recessive
Phenotype Ratio of Offspring
______________________
4.
Heterozygous X Heterozygous
Phenotype Ratio of Offspring
______________________
Questions:
1.
In which of the above crosses will all of the offspring express the dominant phenotype
and be heterozygous? ___________
2.
In which of the above crosses will all of the offspring express the recessive phenotype
and be homozygous? ____________
101
3.
In pea plants purple (P) is dominant to white (p). If you see a purple-flowered plant, what
are its possible genotypes? ________________________
4.
Describe the experiment you would do to determine the correct genotype of the purple
plants.
Exercise 2
Note: The kernels on this ear of corn are either dark or light in color. Both parents of this
ear of corn only possessed dark-colored kernels.
1.
What are the phenotypes of the kernels on your ear of corn?
Phenotype #1 ______________________
Phenotype #2 ______________________
2.
Observe five rows of kernels. Record the number of each phenotype.
Phenotype #1 ______________________
Phenotype #2 ______________________
3.
What is the approximate phenotypic ratio of this ear of corn? _____ : _____
4.
Which allele is dominant? ____________________
5.
Which allele is recessive? ____________________
6.
What are the most probable genotypes and phenotypes of the parent kernels?
7.
Phenotype
Genotype
Parent #1
__________
__________
Parent #2
__________
__________
How many alleles influence this phenotype? __________
Exercise 3
102
Repeat the previous exercise using the new ears of corn that you are given.
1.
Observe five rows of kernels. Record the number of each phenotype.
Phenotype #1 ______________________
Phenotype #2 ______________________
2.
What is the approximate phenotypic ratio of this ear of corn? _____ : _____
3.
What are the most probable genotypes and phenotypes of the parent kernels?
Phenotype
Genotype
Parent #1
__________
__________
Parent #2
__________
__________
Exercise 4: Dihybrid cross
A dihybrid cross involves two characteristics located on different chromosomes. Recall
Mendel’s law of independent assortment which states that alleles of any pair of genes segregate
from each other independently of members of any other gene pair.
In guinea pigs, the allele for black coat color is dominant over the allele for brown and short hair
is dominant over long. If coat color is represented by B, b and hair length by H, h, the genotype
of a double heterozygous pig will the BbHh. Either of the pair of alleles B and b can end up in a
gamete with either of the pair H and h, so the possible combinations of theses alleles in the
gametes will be: BH, Bh, bH, and bh.
What is the genotype of the following guinea pigs:
True breeding black short-haired pig __________________________________________
True breeding brown long-haired pig _________________________________________
Heterozygous black pig with long hair ________________________________________
Heterozygous short-haired pig with brown fur __________________________________
103
(a) A double heterozygous black short-haired pig was mated with a heterozygous black pig
with long hair.
Genotype of heterozygous
black short-haired pig
Genotype of Heterozygous
black pig with long hair
Possible Gametes
Possible Gametes
Use the Punnett square below to work out the genotypes of the offspring of the above cross.
(b)
State the phenotypes of the offspring and give the ratio.
__________________________________________________________________
__________________________________________________________________
Exercise 5: Dihybrid cross (Corn)
104
Observe the kernels on this ear of corn carefully. Each kernel displays two different phenotypic
characteristics and there are four different phenotypic combinations.
1.
What are the two phenotypic characteristics that the kernels display?
Phenotype 1 ____________________ and _____________________
Phenotype 2 ____________________ and _____________________
Phenotype 3 ____________________ and _____________________
Phenotype 4 ____________________ and _____________________
2.
Observe five rows of kernels. Record the number of each phenotype. Record your
results on the board and pool the class results.
Phenotype 1 ____________________
Phenotype 2 ____________________
Phenotype 3 ____________________
Phenotype 4 ____________________
3.
What is the approximate phenotypic ratio of this ear of corn? ____________________
4.
Which alleles are dominant? _____________________ and ______________________
5.
Which alleles are recessive? _____________________ and ______________________
6.
What are the most probable genotypes and phenotypes of the parent kernels?
Genotype
Phenotype
Parent 1 _____________/_____________
________________________
Parent 2 _____________/_____________
________________________
105
Exercise 6: Human Genetics
Most human phenotypes like height, hair color, and stature are complex and influenced by
several genes. A few characteristics, however, are controlled by only a single pair of genes and
follow the rules of Mendelian inheritance. In this exercise, you will attempt to determine your
genotype for a number of these traits. If you demonstrate the dominant form of the gene, you
could be homozygous dominant or heterozygous for that trait. Determining your actual genotype
could involve developing family history or pedigree for that trait. Note that a phenotype that is
dominant will not necessarily be the most abundant one in a population.
1.
Tongue Rolling: The ability to roll your tongue into a U-shape is dominant to the
inability to roll the tongue.
2.
Widow’s Peak: A widow’s peak is a distinct V-shaped point in the frontal hairline. The
presence of a widow’s peak is dominant to a straight hairline.
3.
Earlobe Attachment: Ear lobes may either be free hanging or attached to the side of the
head. To have free-hanging earlobes is dominant to having attached earlobes.
4.
Hitchhiker’s Thumb: The ability to hyperextend or bend the end digit of the thumb
backward past a 45° angle. The presence of a hitchhiker’s thumb is recessive to the
inability to hyperextend the end of the thumb.
5.
Mid-digital hair: The presence of hair (any amount) on the second (middle) digit of the
fingers is dominant to the absence of hair.
6.
Freckles: The presence of freckles is dominant to their absence.
7.
Dimples: The presence of dimples is dominant to their absence.
8.
Thumb Overlap: When folding your hands together, to fold the left thumb over the right
is dominant to folding the right thumb over the left.
9.
PTC Tasting: The ability to taste PTC (phenylthiocarbaminde) is dominant to the
inability to taste. Tasters will detect a bitter flavor.
106
Trait
Tongue
Rolling
2nd finger shorter than
4th
Widow’s
Peak
Earlobe
Attachment
Hitchhiker’s
Thumb
(Last segment can be
bent back 60°)
Mid-digital
Hair
Freckles (face)
Dimples
Thumb
Overlap
My Phenotype
My Possible
Genotype
Roller
or
Nonroller
TT Tt
or
tt
Present
or
Absent
MM or Mm
or
mm
Peak Present
or
Straight
WW Ww
or
ww
Free
or
Attached
FF Ff
or
ff
Present
or
Absent
HH Hh
or
hh
Present
or
Absent
HH Hh
or
hh
Present
or
Absent
FF Ff
or
ff
Present
or
Absent
DD Dd
or
dd
Left
or
Right
TT Tt
or
tt
Right-handedness
LL orLl
or
ll
Present
PTC
Tasting
Taster
or
Nontaster
TT Tt
or
tt
107
CLASS TOTALS
Dominant:
Recessive:
Dominant
Recessive
Dominant:
Recessive:
Dominant:
Recessive:
Dominant:
Recessive:
Dominant:
Recessive:
Dominant:
Recessive:
Dominant:
Recessive:
Dominant:
Recessive:
Dominant
Recessive
Dominant:
Recessive:
Exercise 7: Incomplete Dominance
In simple dominance that we have been investigating so far, the dominant allele is always
expressed when it is present where homozygous or heterozygous. In incomplete dominance,
there are two alleles for a trait, and neither one is truly dominant over the other. With incomplete
dominance, the phenotype of the heterozygote is unlike either of the homozygotes and expresses
an intermediate of both alleles a sort of blending of both phenotypes. A common example of this
is flower color in petunias. Petunias with red flowers have the genotype R1R1. Petunias with
white flowers have a genotype R2R2. A flower that is heterozygous (R1R2) is pink.
If a red-flowered plant is crossed with a white-flowered plant, what is the phenotype and
genotype ratios of the F1 offspring?
If two of the F1 generation were crossed, what would be the genotype and phenotype
ratios of the F2?
108
Exercise 8: Co-dominance
In other cases, when neither allele is dominant, there is not really a blending to give an
intermediate phonotype but both alleles are fully expressed. This is known as co-dominance.
One of the best examples of co-dominance is demonstrated in the coat color of short-horned
cattle. Those individuals with reddish-grey (roan) coats are heterozygous R1R2, and are the
result from a mating between a red (R1R1) shorthorn and a white (R2R2) shorthorn. Roan cattle
do not have roan-colored hairs. Instead, they have both red- and white-colored hairs mixed
together, which at a distance appears to be roan.
What if a roan short-horn cow is mated with a white bull. What will be the genotypic and
phenotypic ratios in the F1 generation?
List the parental genotypes of crosses that would produce at least some…
White offspring: _______________, _______________, _______________
Road offspring: _______________, _______________,
_______________, _______________
109
Exercise 9: Sex Linked
The sex (gender) of humans and other primates is determined by a special pair of “sex
chromosomes,” the X and Y chromosomes. An individual with two X chromosomes if female,
while one X and one Y is male. The genes occurring on the sex chromosomes are called sexlinked genes. Most sex-linked traits are X-linked. That is, they occur on the X chromosome.
The Y chromosome is much smaller than its homologue, the X chromosome. Consequently,
some genes present on the X are absent on the Y chromosome. This allows for sex-linked traits
to be more common in males. Males have only a single copy of the X chromosome. Having
only a single copy of the X chromosome allows for the alleles on that X chromosome to be fully
expressed. Females, with two X chromosomes, can be carriers (heterozygous) for a recessive
trait, but not exhibit the condition.
Color-blindness is a recessive X-linked human trait. If a color-blind man (XrY) fathers
children of a woman with the genotype XRXR, what percentage of the sons would be
color-blind?
A man has a sex-linked form of pattern baldness. From which parent did he receive this
condition? Explain your answer.
a.
mom
b.
dad
c.
no way to tell
d.
both
A girl is color-blind. From which parent did she receive this condition? Explain your
answer.
a.
mom
b.
dad
c.
no way to tell
d.
both parents
110
Exercise 10: Multiple Alleles and co-dominance
Many human traits are controlled by two alleles (i.e., the ability to roll the tongue (T) or the
inability to roll the tongue (t). Some characteristics are controlled by more than two versions of a
gene. These are called multiple alleles. The most well-known of these characteristics is blood
type in humans. The protein “I” on a red blood cell comes in two different forms, type A and
type B. The alleles that code for A and B proteins are co-dominant. Some individuals have cells
that lack this protein altogether. They have type O blood, which is a recessive condition. Thus,
from three alleles, IA, IB, and i, we have a four possible phenotypes of blood: Type A, Type B,
Type O, and Type AB.
Phenotype
Type A
Type B
Type O
Type AB
Possible Genotype
AA or AO
BB or BO
OO
AB
Is it possible for parents both with type AB blood to have a child that is type O? Why or why
not?
In a case of disputed paternity, a child is type O, the mother is type A. Could an individual of
the following blood types be the father?
AB
_________________________
B
_________________________
A
_________________________
O
_________________________
111
Genetics Review Questions
You must indicate what the letter symbols you use mean and you must include the Punnett
square in all answers where appropriate.
1.
2.
3.
In Labrador retrievers (a breed of dog) black coat color is dominant to brown.
(a)
What would be the genotype of a heterozygous black dog?
(b)
If a homozygous black dog is crossed with a brown dog, what will be the
phenotypic ratio of the offspring?
(c)
If two black dogs from (b) above were crossed, what phenotypic ratio would
you expect in the offspring?
(d)
If a heterozygous black dog is crossed with a brown dog, what phenotypic
ratio would result?
In humans normal skin pigmentation is dominant to albinism (lack of the pigment
melanin in the skin). Explain how two normal pigmented parents can produce an
albino child.
In pea plants round seed shape is dominant to wrinkled and yellow seed color is
dominant to green. Give the genotypes of the following:
(a)
True breeding round yellow seed plants
112
(b)
Plants with green wrinkled seeds
(c)
Plants whose seeds are wrinkled and which are heterozygous for yellow seed
color.
(d)
Plants whose seeds are green and which are heterozygous for round seed color
(e)
Suppose a plant with green wrinkled seeds is crossed a double heterozygous
plant with round yellow seeds.
(i) State the gametes a green wrinkled plant would produce.
(ii) State the genotype and gametes the double heterozygous would produce.
(iii)What phenotypes would this cross produce and in what ratios?
4.
In cattle, red coat is incompletely dominant over white coat color. The intermediate
type is called roan, which is a mixture of red and white hair. Give the genotypes and
phenotypes (and their proportions) of a cross between two roan animals.
5.
If a child is blood type O, and the mother is B, could an individual of the following
blood types be the father? Explain your answer.
(a)
AB
(b)
B
113
6.
Red-green color blindness is a recessive X-linked trait. A woman with normal vision
whose father was color blind, married a color blind man.
(a)
What are the phenotypes of their sons and daughters?
(b)
Explain why the sons of a man with normal vision will not all necessarily
have normal vision.
114
EXERCISE 11
PROTIST, FUNGAL AND PLANT DIVERISTY
LEARNING OBJECTIVES





Describe the diversity that exists among the protists.
Identify the characteristics of fungi.
Explain the alteration of generations in plants.
Outline the divers features of plant structure and reproduction.
Explain the features that allow land plants to successfully inhabit the terrestrial
environment
PROTISTA
This group includes a number of quite different organisms, which have been placed together
because a few basic similarities they share: they are all eukaryotic with more than one
chromosome and with a clearly defined nucleus and organelles, and divide by mitosis and
meiosis. Most are single celled but there are also many multi-cellular species. These organisms
have been placed together (for convenience?) in a group between prokaryotes and more complex
eukaryotes and in many cases there is no true genetic relationship between many of the species.
Hence the differences between them abound.
Differences between protists:
1.
Method of feeding: autotrophs, predators, parasites and decomposers are all members of
this group.
2.
Method of locomotion: Members utilize, flagella, cilia and pseudopods.
3.
Size: Both microscopic and macroscopic species exist.
4.
Cell wall: Some species have cell wall (made of cellulose) and others are wall-less.
5.
Habitat: Habitats include fresh water, the marine environment and parasitic associations.
Exercise 1: Macroscopic protists
115
Observe the brown, red and green marine algae and make drawings of at least two types, to show
their body form.
Exercise 2: Microscopic protists
Use your microscope (x 40 objective) to make drawings of the following protists: Euglena,
Paramecium, Amoeba, and Spirogyra. Note the presence of the following structures wherever
they occur and label them on your drawing: cell wall, plasma membrane, nucleus, chloroplast,
pseudopod, cilia, food vacuole.
Euglena
Paramecium
Amoeba
Spirogyra
FUNGI
116
The fungi are spore-bearing, heterotrophic with absorptive nutrition, which reproduce both
sexually and asexually. Most of them are saprobes but many parasitic species also exist. The
group includes both microscopic types and macroscopic types. In terms of body form, most are
made up of thread-like filaments called hyphae. The mass of hyphae is called mycelium. Yeasts
are unicellular fungi (microscopic). They include species that are used in the making of bread
and alcoholic beverages as well as parasitic ones that cause yeast infections.
Exercise 3: Filamentous fungi
Use your microscope to draw portions of the slides of Rhizopus (the bread mold) and
Penicillium. Note the following structures and label them on your drawing; hyphae, spornagia,
spores.
Rhizopus
Penicillium
Exercise 4: Unicellular fungi: yeasts
117
Make drawings of some yeast cells from the slides provided.
Exercise 5: Macroscopic fungi
Observe the specimens of macroscopic fungi on display: mushrooms, puff balls, shelf fungi, etc.
PLANT DIVERSITY
118
Plants are photosynthetic organisms which all contain chlorophyll. Apart from those unifying
features, plants display a number of differences:
1.
Some plants have a body plan in which roots, stems and leaves are present. Less
complex plant do not have this differentiation.
2.
Some plants are vascular which means that they have transport tissues. Phloem
transports manufactured carbohydrate and xylem transports water. Other plants are
non-vascular.
3.
Some plants need water for the fertilization of the female gamete by the male, others use
agents such as wind or insects to transport the male gamete.
4.
Some plants produce seeds and others do not.
5.
Some seed-bearing plants, produce flowers and fruit and so the seed development takes
place inside the fruit. Other seed-bearing plants produce naked seed.
6.
Plants display a life cycle which alternates between two phases known as generations.
The gametophyte generation produce gametes and the sporophyte generation produces
spores. In some plants the gametophyte generation is dominant and in others the
sporophyte generation is dominant. Dominant means that this is the part of the life cycle
which is physically larger and the stage in which the plant spends most of its life.
Exercise 6: Bryophytes e.g. mosses
Make a drawing of the plant body of the moss. Label the following structures on your diagram:
rhizoid, stem-like structure, leaf-like structure, gametophyte, sporophyte, capsule.
Drawing of moss
119
Which generation is dominant? ____________________________________________________
Is the dominant haploid or diploid? _________________________________________________
What is the function of the rhizoids? ________________________________________________
Why are these plants found only in moist shady areas?
______________________________________________________________________________
______________________________________________________________________________
Exercise 7: Ferns
120
(a)
Draw a part of the underside of a fern frond.
What are the brown structures called? _______________________________________________
(b)
Use a needle and tease out one of the brown structures onto a microscope slide and
observe under the dissecting microscope.
What are these individual structures you teased out called? ________________________
What do they produce? ____________________________________________________
Which generation does the fern frond represent? Gametophyte or sporophyte?
________________________________________________________________________
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Gently remove one of the fern prothalli (gametophyte) from the jar. Place it on a microscope
slide in a drop of water from the jar and cover with a cover slip. Observe using the low power of
your microscope and draw.
Which generation of the fern plant is this? ___________________________________________
Is it haploid or diploid? __________________________________________________________
Describe what happens on the prothallus (gametophyte).
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
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Exercise 8: Gymnosperms e.g. pine
Make a drawing of a male and female pine cone.
What is the function of the male cone? ______________________________________________
What happens on the ‘leaves’ on the female cone?
______________________________________________________________________________
______________________________________________________________________________
Explain why these plants are called ‘gymnosperms’?
______________________________________________________________________________
______________________________________________________________________________
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Exercise 8: Angiosperms: Flowering plants
(a)
Make a drawing of the half flower and label all the parts. Give the function of each of
the parts you have labeled.
What part of the flower becomes the seed? _____________
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The fruit? _____________
Exercise 9: Summary of Plant Characteristics
Indicate whether a plant group has a particular characteristic by putting a check mark in the
relevant column.
Characteristic
Water needed for fertilization
Plant body has distinct roots,
stems, leaves
Rhizoids present
Sporophyte generation
dominant
Vascular
Seeds: naked
Seeds: enclosed
Flowers
Fruit
Moss
Fern
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Gymnosperm
Angiosperm
EXERCISE 12
Animal Diversity
LEARNING OBJECTIVES
 Compare and contrast the body plan of different animal groups.
 Assign animals to their correct phylum based on their characteristics.
 Identify those characteristic that are important for successful terrestrial life.
INTRODUCTION
Animal bodies display a number of features that can be used in the identification of the different
animal groups.
Cephalization: a concentration of nerve and sensory cells in one area (anterior or head region).
This is the area of the animal that first encounters the stimuli in the environment.
Symmetry: Animals display radial or bilateral symmetry. In radial symmetry, the body
parts of the animal are arranged around a central point e.g. star fish. There are several axes that
can divide the body into mirror images of each other. Animals with bilateral symmetry have
only one axis that can produce mirror images. They are usually cephalized, with a definite head
region at the anterior of the body, a posterior region and dorsal (back) and ventral (underside or
belly) regions e.g. earthworms.
Segmentation: Many animal bodies are divided into interconnecting sections that are repeated
one after the other along the body. This is very obvious in earthworms.
Type of gut: The gut or digestive system may be incomplete or sac-like with only one opening
fo feeding and getting rid of waste. A complete or tubular gut, has two openings, a mouth at
one end and an anus at the other.
Coelom: A coelom is a cavity or space between the body wall and the digestive system. The
coelom protects and cushions the internal organs of the animal.
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Exercise 1: Identify examples of different animal groups.
Fig. 1 is a chart which shows a simplified classification of the major animal groups. Use the
specimen display to locate examples of each of the groups listed on the chart. Write in at least
one example of each group.
Sponges
Cnidarians
Flatworms
Annelids
Invertebrates
Mollusks
Roundworms
Echinodrems
Arthropods
Crustaceans
Arachnids
Insects
Myriapods
All animals
Fish
Amphibia
Reptiles
Vertebrates
Birds
Mammals
Figure 1: Classification of Animals
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Draw one animal belonging to each of the invertebrate groups.
Sponge
Cnidarian
Flatworm
Roundworm
Annelid
Mollusk
Arthropod
Echinoderm
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INVERTEBRATES
Exercise 2: Characteristics of Invertebrates
Some of the characteristics listed in the Table 1 are visible when viewing an animal externally
and others are not. Observe the specimen display and check off the features characteristic of
each group. (Use your textbook to get information about features that can only be seen visible
internally).
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Characteristic
Cells organized into
tissues
Organ systems
Coelom
Cephalization
Segmentation
Appendages
Symmetry: bilateral
Symmetry: radial
Type of gut: sac
Type of gut: tubular
Sponges
Cnidarians
Flatworms
Annelids
Mollusks
Roundworms Echinoderms Arthropods
Table 1: Characteristics of Invertebrates
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VERTEBRATES
All vertebrates have the following features in common: a coelom, a circulatory system and an
internal skeleton. The skeleton consists of a backbone or vertebral column which encloses the
spinal cord and a skull or cranium which houses the brain. Apart from these unifying features,
vertebrate groups display some marked differences in their other characteristics.
Exercise 3: Characteristics of Vertebrates
Observe the vertebrate specimens on display and compare Table 2 with their characteristics (for
those features that are not visible externally, use your textbook to get the information).
Characteristic
Type of body covering
Breathing organs
Habitat
Type of appendages
Amniote egg?
Internal or external
fertilization?
Fish
Amphibia
Reptiles
Table 2: Characteristics of Vertebrates
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Birds
Mammals
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