BCLN BIOLOGY 12 – Rev July 2014
Complete the following notes and questions as you work through the related lessons.
You are required to have this package completed BEFORE you write your unit test. Do your best and ask questions about anything that you don't understand BEFORE you write the unit test.
Homeostasis:
Examples:
1. Blood Glucose Concentration remains about 0.01%
2. PH of blood is always near 7.4 (slightly basic)
3. Blood pressure in the brachial artery averages near 120/80
4. Blood temperature averages ~ 37 ° C
5. Pancreatic Juice (pH 8.5) neutralizes stomach acids so that food entering the small intestine is basic.
6. CO
2 concentration in our blood stimulates our breathing.
Negative Feedback:
Control centers in the
_that cause specific body reactions.
Once normalcy is reached, the
(This is why the process is called
_). release
is NO LONGER stimulated.
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1
2
3
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BCLN BIOLOGY 12 – Rev July 2014

Positive Feedback:
Instead of achieving normalcy,
BCLN BIOLOGY 12 – Rev July 2014
Negative Feedback tends to
Positive Feedback leads to
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.

BCLN BIOLOGY 12 – Rev July 2014
1. A woman is being tested for diabetes mellitus. Her blood glucose levels are measured and recorded over a period of time (data given below). Please graph the data and answer the associated questions.
Graphing Tips:
 the independent variable is always placed on the x-axis (in this case, time)
 the dependent variable is always placed on the y-axis (in this case, blood glucose levels as they are dependent on the time)
 each axis needs an informative title that includes units of measurement such as hours and mg/dL
 the graph needs an informative title
 each square on the graph must represent a consistent value such as 1 hour (x-axis) or 20 mg/dL (y-axis)
Table 1. Blood Glucose Levels in Patient X over Time.
Time (h)
Blood Glucose
Levels (mg/dL)
0
1
2
3
4
5
100
110
100
80
90
100
Figure 1. Blood Glucose Levels in Patient X over Time
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BCLN BIOLOGY 12 – Rev July 2014 a. The normal range for blood glucose levels is 70-110 mg/dl. Does Patient X always remain within the normal range? b. Does Patient X have any apparent problems with glucose regulation? W hy or why not? c. Which type of feedback mechanism (positive or negative) is used to regulate blood glucose levels? Explain your reasoning.
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BCLN BIOLOGY 12 – Rev July 2014
Water
– The Universal Solvent
Because water is the substance that makes life possible as we know it on Earth, astronomers hope to find evidence of water on newly discovered plants orbiting distant stars.
Life on Earth began in the water and evolved there for 3 billion years before spreading onto land.
Terrestrial organisms are still tied to water. In fact, most cells are surrounded by water and cells themselves are about 70-95% water.
Background Information
Life as we know it, is based on the
. To be "organic" a molecule must have a carbon atom in it. For example, vinegar (CH
3
CH
2
OH) is organic, whereas is not.
The organic molecules in living things are easily grouped into four types. Understanding these four biochemicals is the focus of Unit 2.
If Not Organic, Why is Water so Incredibly Important?
What happens to the quality of life if the chemical conditions of living things change?
In the formation of , atoms must bond together to form . In order to do this, the around the various nuclei in the compound must also be stable. This stability can be achieved through some degree of
between the atoms.
If the atoms share the electrons reasonably equally, their association is termed bond.
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BCLN BIOLOGY 12 – Rev July 2014
Ionic Bonds
The alternative is a very unequal sharing of electrons. This is called an
where it seems as though one atom actually gives
. Neutral atoms become when they lose electrons and
when they gain electrons.
In between these two extremes is what is termed
. Polar covalent molecules have (regions with slight positive and negative natures). A water molecule is an example of this kind of molecule.
Structure of Water
In a covalent bond atoms to become stable. If the electrons in a covalent bond are not shared equally by the two atoms, the molecule is then called a .
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BCLN BIOLOGY 12 – Rev July 2014
Polar Molecules
Any molecule that ends with a different charge is called a .
Hence it would be a . One end being the negative dipole and the other being the positive dipole.
Therefore, water molecules behave as with one another. causes water to have some degree of structure that extends beyond the individual molecules and cause a community water effect. The overall property is called , i.e. the attraction of the
.
This means that water molecules are to one another. The negative charge on the oxygen attracts the positively charged hydrogen some distance away to produce a weak bond called a
.
YOU SHOULD WATCH THE STRUCTURE OF WATER VIDEO
BEFORE PROCEEDING ANY FURTHER!
Hydrogen Bonding
Although hydrogen bonds are weak, the vast number of these bonds gives water its unique properties. Each water molecule can form hydrogen bonds with up to neighbors.
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BCLN BIOLOGY 12 – Rev July 2014
Water is the Solvent of Life
A is a mixture of one or more soluble substances, called
, dissolved in a liquid called the .
A sugar cube in a glass of water will eventually dissolve to form a uniform mixture of sugar and water. The dissolving agent is the and the substance that is dissolved is the . In our example, water is the solvent and sugar the solute.
Can you identify the solvent and solute in each of the following solutions?
Example 1: 15 g baking soda and 100 ml of water?
Solvent:
Solute:
Example 2: Nail polish removed by acetone?
Solvent:
Solute:
Example 3: 1.00L ethylene glycol and 875 mL water?
Solvent:
Solute:
Example 4: Chromium dissolved in hydrochloric acid?
Solvent:
Solute:
Some Key Properties of Water Include:
1. Water acts as a Solvent
Water substances
and is able to dissolve many chemical especially other
. Since blood is mainly water, the ability of water to dissolve and transport substances greatly aids in bringing about necessary .
2. Water acts as a Temperature Moderator
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BCLN BIOLOGY 12 – Rev July 2014
Water moderates temperature and climate (both internal and external climates).
Water can absorb a great deal of releases heat slowly. This property is referred to as a
.
. Water also
As a liquid evaporates the most energetic molecules are carried away leaving the lower kinetic energy molecules behind which cools the surface of the liquid that remains - .
Internal example -
External example - Oceans keep surrounding land masses cool in summer and warmer in winter.
3. Water has a "weird" Density
Liquid water is than ice (very rare for compounds). Most materials contract as they solidify, but water expands. Therefore, ice forms on top of water
levels. This oddity has important consequences for life. If ice sank, eventually all ponds, lakes, and even oceans would freeze solid. During the summer, only the upper few inches of the ocean would thaw. Instead, the surface layer of ice insulates liquid water below, preventing it from freezing and allowing life to exist under the frozen surface.
4. Water is Transparent
Light organisms below. of water to the
5. Water is Cohesive/Adhesive
Water molecules
This keeps surfaces
.
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BCLN BIOLOGY 12 – Rev July 2014
. Diffusion of gases occurs much more efficiently
moist surfaces. (sticking to each other) among water molecules plays a key role in the transport of water against gravity in plants. , is a measure of the force necessary to stretch or break the surface of a liquid and is related to cohesion.
Water has a than most other liquids because hydrogen bonds among surface water molecules
the surface. Water behaves as if covered by an invisible film. Some animals can
on water without breaking the surface.
(clinging of one substance to another) contributes too, as water adheres to the walls of the blood vessels.
**** Note: Focus on the properties of water that apply to the human body.****
YOU SHOULD WATCH THE FUNCTION OF WATER VIDEO
BEFORE PROCEEDING ANY FURTHER!
What are four important functions of water in the human body?
Example 1:
Example 2:
Example 3:
Example 4:
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BCLN BIOLOGY 12 – Rev July 2014
2. What type of bonds are found between hydrogen and oxygen atoms within a single water molecule? (1 mark)
3. What type of bonds form between two or more water molecules? (1 mark)
5. List 3 everyday examples of the cohesive and/or adhesive properties of water. (3 marks)
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BCLN BIOLOGY 12 – Rev July 2014
6 Use several examples each to explain how water is essential to life on Earth as we know it with respect to the following properties: a. Water acts as a Solvent (3 marks) b. Water acts as a Temperature Moderator (3 marks) c. Water acts as a Lubricant and Transportation Facilitator (3 marks)
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BCLN BIOLOGY 12 – Rev July 2014
7 Please indicate whether the statements below are true or false. Please correct any false statements.
T / F a. Water molecules can attract other water molecules by hydrogen bonding.
T / F b. Hydrogen bonds are stronger than ionic or covalent bonds.
T / F c. The majority of our cellular reactions occur in water.
T / F d. Large lakes and oceans tend to moderate local temperatures.
T / F e. Water is an organic molecule.
pH
Organisms are sensitive to changes in pH (
).
Acids
An is a substance that in a solution. For example when hydrochloric acid is added to water, hydrochloric acid dissociates to form hydrogen ions and chloride ions:
HCL  H
+
+ Cl
-
The addition of H
+ makes a solution more acidic.
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BCLN BIOLOGY 12 – Rev July 2014
Bases
A base is a substance that increases the hydroxide ion concentration in a solution.
For example when sodium hydroxide is added to water, sodium hydroxide dissociates to form sodium ions and hydroxide ions:
NaOH  Na
+
+ OH
-
Solution with more are basic solutions.
(the The pH scale is used to describe how opposite of acidic) a solution is.
YOU SHOULD WATCH THE ACID AND BASES VIDEO AND THE pH SCALE VIDEO
BEFORE PROCEEDING ANY FURTHER!
pH Scale
The pH scale, ranging from 1 to 14, compresses the range of concentrations by employing logarithms. In other words every number on the pH scale is a multiple of 10. pH = -log [H
+
] or [H
+
] = 10
-pH
A pH of 7 is a neutral pH where the -
. [H
+
] = [OH
-
]
A pH that ranges between 7 and 14 has more hydroxide ions than hydrogen ions making it a basic solution and a pH that ranges between 1 and 7 has more hydrogen ions than hydroxide ions making it an acidic solution. W e can calculate the the difference in hydrogen ion concentrations at different pH levels by multiplying or dividing by 10.
For example a pH 6 has more H
+
more H
+ than pH 5 and so on. than at pH 7. A pH of 3 has
Try the following pH comparisons:
Example 1: pH of 12 has more H
+ than a pH of 15
Example 2: H of 12 has more H
+ than a pH of 15
The pH scale is just a comparison between the [H
+
] and [OH
-
].
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BCLN BIOLOGY 12 – Rev July 2014
YOU SHOULD WATCH THE SECOND pH SCALE VIDEO and THE BUFFERS
BEFORE PROCEEDING ANY FURTHER!
Buffers
Most the
which control
in your body, can only operate at certain
levels. If pH levels change too drastically these biochemicals will denature
(lose their shape) and no longer function properly.
Example:
•
•
Blood must be at a pH close to or else we may become ill.
At the wrong pH the blood cannot transport as efficiently.
As you can see then the by changes to the H
+ and OH
- concentrations away from their
.
To maintain cellular pH values at a constant level,
.
can be disrupted
The function of Buffers is to
when H
+ or OH
- is added to the solution.
Buffers are
.
Buffers accept hydrogen ions from the solution when they are in excess and donate hydrogen ions when they have been depleted.
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Note: The buffer keeps pH constant
.
BCLN BIOLOGY 12 – Rev July 2014
Acids are molecules that dissociate to release respect water acts as a ions. In this
. HCI on the other hand is a
because it dissociates to a much greater extent.
Systems with HCI in them have a lot of free floating around.
Bases are molecules that release
. Bases have a
. Molecules like because the H+ in an acidic environment will combine with OH- from a base and form
.
YOU SHOULD WATCH THE DEMONSTRATIONS OF BUFFERS AT WORK
VIDEO BEFORE PROCEEDING ANY FURTHER!
Note: The first graph shows pH change without a buffer, while the second graph shows pH change with a buffer.
1. Please define the following terms (4 marks): a. acid b. base c. pH scale
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BCLN BIOLOGY 12 – Rev July 2014 d. buffer
2. Please indicate whether the following pH values represent an acidic, basic or neutral solution. (2 marks) a. pH 0: b. pH 12: c. pH 7: d. pH 3:
3. Hydrochloric acid (HCl), a strong acid, is added to a beaker of pure water (3 marks): a. What is the pH of the pure water in the beaker before the acid is added? b. How does the hydrogen ion concentration of the solution in the beaker change does after the acid is added? c. What happens to the pH of the solution in the beaker as the acid is added?
4. How much has the hydrogen ion concentration changed in a solution if its pH value goes from 6 to 4? Remember to indicate whether this change represents an increase or decrease in hydrogen ion concentration. (1 mark)
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BCLN BIOLOGY 12 – Rev July 2014
5. pH balance is very important to biological systems. a. Why? (1 mark) b. What prevents rapid or large changes in pH in biological systems? (1 mark) c. Give an example of where pH balance is important and regulated in a living organism. (1 mark)
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BCLN BIOLOGY 12 – Rev July 2014
U1L1 PRACTICE: INTRODUCTION
1. A woman is being tested for diabetes mellitus. Her blood glucose levels are measured and recorded over a period of time (data given below). Please graph the data and answer the associated questions. a. The normal range for blood glucose levels is 70-110 mg/d. Does Patient X always remain within the normal range?
- Yes…ranges from 80-110 mg/dl b. Does Patient X have any apparent problems with glucose regulation? W hy or why not?
- No…blood glucose levels appear to remain within a normal range suggesting homeostatic mechanisms are functioning correctly to regulate blood glucose levels c. W hich type of feedback mechanism (positive or negative) is used to regulate blood glucose levels? Explain your reasoning.
- negative feedback loop as the process is maintaining normalcy (blood glucose between 70-110 mg/dl) as opposed to moving levels towards an extreme as would a positive feedback loop
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BCLN BIOLOGY 12 – Rev July 2014
U1L3 PRACTICE: WATER
1. Sketch a ball and stick diagram of a water molecule. Label the atoms and indicate the partial charges that exist in a water molecule. (2 marks)
2. W hat type of bonds are found between hydrogen and oxygen atoms within a single water molecule? (1 mark)
- Covalent bond (intramolecular)
3. W hat type of bonds form between two or more water molecules? (1 mark)
- Hydrogen bond (intermolecular)
4. Use a diagram with 5 water molecules to illustrate hydrogen bonding between water molecules
(start with one molecule in the middle). How many water molecules can hydrogen bond with a single water molecule? (3 marks)
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BCLN BIOLOGY 12 – Rev July 2014
5. List 3 everyday examples of the cohesive and/or adhesive properties of water. (3 marks)
- answers may vary but may include; o movement of water up plant stems o the ability of water bugs to "stand" on water o water clinging to a surface such as blood vessels
8 W ater is a
(especially other molecule. W ater many substances molecules). This property makes water an excellent
. (2)
9 Use several examples each to explain how water is essential to life on Earth as we know it with respect to the following properties: a. W ater acts as a Solvent (3 marks)
- dissolves charged and polar molecules such as salts which can then be transported throughout the body
- dissolves charged such as salts that can then react with one another to form new ionic compounds b. W ater acts as a Temperature Moderator (3 marks)
- the polarity/hydrogen bonding of water makes it slow to heat and cool meaning that it helps to maintain a relatively constant body temperature and global temperature
- the polarity/hydrogen bonding of water also results in it having a high heat of evaporation making it (in the form of perspiration) an effective coolant on the surface of the skin c. W ater acts as a Lubricant and Transportation Facilitator (3 marks)
- the polarity/hydrogen bonding of water makes it cohesive/adhesive such that it fills and flows through vessels easily making it an effective transport medium
- the polarity/hydrogen bonding of water allows it to remain in a liquid state at body temperature 9as opposed to a gas as is comparable for most similar molecules) making it an effective transport medium
- the polar nature of water allows it to stick to other surfaces (adhesion)
which provides lubrication required for the movement of joints, blinking of
eyes etc.
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BCLN BIOLOGY 12 – Rev July 2014
10 Please indicate whether the statements below are true or false. Please correct any false statements.
T / F a. W ater molecules can attract other water molecules by hydrogen bonding.
T / F b. Hydrogen bonds are stronger than ionic or covalent bonds.
T / F c. The majority of our cellular reactions occur in water.
T / F d. Large lakes and oceans tend to moderate local temperatures.
T / F e. W ater is an organic molecule.
U1L4 PRACTICE: pH, ACIDS AND BASES
1. Please define the following terms (4 marks): a. Acid
= compound that releases hydrogen ions in aqueous solutions (increase H + solution) ions in b. Base
= compound that releases hydroxide ions in aqueous solutions (increase OH - solution) ions in c. pH scale
= describes how acidic or basic a solution is, a negative log scale referring to the concentration of hydrogen ions (H + ) within a solution d. buffer
= a substance that resists changes in pH despite the addition of an acid or base
2. Please indicate whether the following pH values represent an acidic, basic or neutral solution. (2 marks) a. pH 0: b. pH 12:
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BCLN BIOLOGY 12 – Rev July 2014 c. pH 7: d. pH 3:
3. Hydrochloric acid (HCl), a strong acid, is added to a beaker of pure water (3 marks): a. W hat is the pH of the pure water in the beaker before the acid is added?
- by definition the pH of pure water is 7 (neutral) b. How does the hydrogen ion concentration of the solution in the beaker change does after the acid is added?
- by definition acids increase the hydrogen ion concentration of a solution c. W hat happens to the pH of the solution in the beaker as the acid is added?
- pH decreases
4. How much has the hydrogen ion concentration changed in a solution if its pH value goes from 6 to 4? Remember to indicate whether this change represents an increase or decrease in hydrogen ion concentration. (1 mark)
Thus, the hydrogen ion concentration has increased a 100 fold when pH shifts from 6 to 4.
5. pH balance is very important to biological systems. a. W hy? (1 mark)
- Because many cellular activities require the action of enzymes which are proteins whose three-dimensional structures and accompanying functions are dependent on a particular pH…changing the pH changes the structure
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BCLN BIOLOGY 12 – Rev July 2014 and inhibits the enzyme's functions and therefore, inhibits cellular activities b. W hat prevents rapid or large changes in pH in biological systems? (1 mark)
- buffers c. Give an example of where pH balance is important and regulated in a living organism. (1 mark)
- Answers may vary but may include; o in the blood (pH ~7.4) to maintain protein structure such as that of hemoglobin…regulated using the bicarbonate buffer system and hemoglobin itself o in the stomach (pH ~ 2) to ensure activation of digestive enzymes such as pepsin while also beginning to denature (unfold) ingested proteins…regulated by parietal cells that release hydrochloric acid o in the small intestine (pH ~ 7) to ensure the activation of digestive enzymes such as trypsin…regulated by bicarbonate released into the small intestine by the pancreas
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