LAB REVIEW
Unit # 1- Labs
DIFFUSION, OSMOSIS, SA:V,
ENZYME CATALYSIS, &
MACROMOLECULES
•LAB # 1: OSMOSIS IN PLANT CELLS
• In
this activity, you investigated water
potential by immersing potato cores in
sucrose solutions of various molarity and
determining the change in mass, if any, of
the cores.
• Each
group of 4 (four) potato cores were
weighed and the weight recorded on the
table provided.
Gathering Data
• Potatoes
were placed in the labeled cups
and 100 mL of the assigned sucrose
solutions were poured into the cups.
• Solutions ranged from 0.0 M to 1.0 M
• The potato cores were then covered and
set aside until the end of all labs.
• Finally, potato cores were
weighed again & the mass
was recorded on the table.
•Class Averages – 1ST period
Contents
in Cup
Temp
Initial
Mass
Final
Mass
Change in
Mass
%
Change
in Mass
4.7
5.2
0.5
9.7
3.0
13
10.0
9.5
13.3
0.3
6.5
0.3
22° C
13.5 14.0
0.5
0.6 M sucrose
22° C
11.0 10.0
-1.0
0.8 M sucrose
22° C
5.3
10.0
5.0
9.5
-0.3
-0.5
1.0 M sucrose
22° C
9.7
8.0
-1.7
0.0 M sucrose
(distilled water) 22°
0.2 M sucrose
0.4 M sucrose
C
22° C
Change in
Mass
(Class Average)
•Class Averages – 4th Period
Contents
in Cup
Temp
Initial
Mass
Final
Mass
Change in
Mass
0.0 M sucrose
(distilled water)
22° C
4.79
5.29
0.5
0.2 M sucrose
22° C
3.0
9.5
6.5
22° C
8.6
9.0
0.4
7.2
86
4.5
5.3
3.3
9.7
8.0
8.3
4.4
5.0
3.5
8.0
.08
-0.3
-0.1
-0.3
0.2
-1.7
0.4 M sucrose
0.6 M sucrose
22° C
0.8 M sucrose
22° C
1.0 M sucrose
22° C
%
Change in
Change
Mass
(Class Average)
in Mass
•Class Averages – 6th Period
Contents
in Cup
Temp
Initial
Mass
Final
Mass
Change in
Mass
%
Change
in Mass
0.0 M sucrose
(distilled water)
22° C
5.2
0.5
11.0 10.5
3.2
9.9
8.6 9.0
11.3 10.4
-0.5
6.7
0.4
-0.9
22° C
7.2
8.0
0.8
0.8 M sucrose
22° C
5.3
4.5
5.0
4.4
-0.3
-0.1
1.0 M sucrose
22° C
3.3
3.5
0.2
0.2 M sucrose
0.4 M sucrose
0.6 M sucrose
22° C
22° C
4.7
Change in Mass
(Class Average)
•Calculating % Change in Mass
• Formula
• Final
for calculations:
mass – Initial mass x 100
Initial mass
F – I x 100
I
•Calculating % Change in Mass
1) Establish your starting value and write it down.
Example: starting value is a mass of 200 grams.
2) Establish your final value.
Example: final value of your mass after an experiment is
180 grams.
3) Subtract the starting value from the final value and
label it as "Change."
Example: subtract 200 grams from 180 grams to yield a
change of negative 20 grams.
4) Calculate percent change by dividing the change by
the starting value.
Example: divide negative 20 by 200 to get negative 0.1.
5) Multiply the product by 100 to calculate a percentage
decrease of 10%.
Example: -0.1 X 100 = -10%
•
•% Change in Potato Cores
COMBINED AVERAGES FOR CLASSES
Contents
in Cup
1st Pd
4th pd
6.85%
8.04%
10.64%
8.51%
0.2 M sucrose
109.49%
216.67%
102.43%
142.86%
0.4 M sucrose
3.7%
4.65%
-1.7%
2.22%
0.6 M sucrose
-9.09%
3.81%
11.11%
1.94%
0.8 M sucrose
-5.35%
-3.94%
-3.94
-4.41%
1.0 M sucrose
-17.5%
-5.74%
6.06
-5.72%
0.0 M sucrose
(distilled water)
6th pd
TOTAL %
CHANGE
AVERAGE
•Graphing Your Results
• You
will graph your data and
use the graph to determine a
value for C.
• Using
the experimentally
determined value for C, you will
then calculate a value for Ψs.
•After determining C graphically, use
formulas to calculate solute potential
and water potential.
Ψ = Ψp + Ψs
Ψs = -iCRT
i=
The number of particles
the molecule will make in
water; for NaCl this would
be 2; for sucrose or
glucose, this number is 1
C = Molar concentration (from
your experimental data)
R = Pressure constant = 0.0831
liter bar/mole K
T = Temperature in degrees
Kelvin = 273 + °C of
solution
Water potential ( ) =
pressure potential ( ) + solute potential ( )
Pressure potential ( ):
In a plant cell, pressure
exerted by the rigid cell wall
that limits further water
uptake.
Solute potential ( ):
The effect of solute
concentration. Pure water
at atmospheric pressure has
a solute potential of zero. As
solute is added, the value
for solute potential becomes
more negative. This causes
water potential to decrease
also.
In sum, as solute is added,
the water potential of a
solution drops, and water will
tend to move into the
solution.
In this laboratory we use bars as the unit of measure for water
potential; 1 bar = approximately 1 atmosphere.
•DIFFUSION WITH DIALYSIS TUBING
•
•
•
•
•
In this activity, you investigated diffusion across a
simulated selectively-permeable membrane.
Using a starch-indicator (IKI) in solution with distilled
water, you simulated the ECM of a cell in a clear cup.
Then a dialysis tubing filled with a sugar-starch solution,
was used to simulate a cell in a selectively permeable
membrane.
All solutions were checked with a glucose testing strip
for the presence of sugar and the data was recorded.
The cup was set aside for a few minutes and then
observed.
STARCH
GLUCOSE
H 2O
IKI
•RESULTS
• Within
a few minutes, you should have
noticed the solution inside the bag
turning dark blue/black.
• There
should have been no significant
color change within the ECM.
• Solutions
were again tested for the
presence of glucose.
• Determinations
were made based on this
evidence as to the movement of
molecules.
•RESULTS
•
Glucose: moved out of the bag.
•
The concentration of glucose inside the bag is higher
than outside the bag and the glucose molecule is
smaller than the pore size of the membrane.
IKI solution: moved into the bag.
•
•
The concentration of IKI outside the bag is higher than
inside the bag and the IKI molecule is smaller than
the pore size of the membrane.
Starch: No movement.
•
•
The starch molecule is larger than the pore size of the
membrane
Water: Moved into the bag.
•
•
The concentration of water outside the bag is higher
than inside the bag and the water molecule is smaller
than the pore size of the membrane.
CELL DIFFUSION RATES
•
In this activity, you investigated diffusion into
cells based on surface area to volume ratios.
•
Three cubes of various sizes were cut from
agar.
•
•
•
1 cm X 1 cm X 1 cm
2 cm X 2 cm X 2 cm
3 cm X 3 cm X 3 cm
•
The surface area and volumes were
calculated for each cube.
•
Cubes were then submersed into acetic acid
(vinegar) and set aside for several minutes.
•The white area of the cell was cut
away.
•
•
The cubes were measured after all the white area was
removed and the surface area and volumes were recalculated.
Based on the remaining SA:V ratios, the % of “dead”
cytoplasm was determined and recorded.
Cell A
3 cm X 3 cm X 3 cm
Cell B
1 cm x 1 cm x 1 cm
•Enzyme Catalysis
In this activity, you investigated “optimal
conditions” for enzyme function.
• Using a mixture of water and H2O2 (hydrogen
peroxide), the enzyme catalase was added.
•
•
•
•
Conditions were varied from group to group to
include:
•
•
•
•
•
Catalase breaks down H2O2 into water and oxygen.
The oxygen can be measured by a gas pressure
sensor which indicates the rate and duration of this
catalysis.
Temperature (room temp, heat, ice)
Salinity (NaCl solution)
pH (acid, base, & neutral)
Amount of enzyme (doubled amount of catalase)
Rates were collected and recorded for each
condition.
•Data Collected:
Class Averages
Room
Temp.
Heated Cooled
(Boiling
(Ice)
Water
for 5
Acid Base Neutral
(water)
Salt
Double
Concentration
143
420
min)
Class
Average
Time in
Seconds
334
300
224
180
440
90
•MACROMOLECULE TESTING
• In
•
this lab, you tested for the presence of
Simple carbohydrates (sugars)
• Complex carbohydrates (starches)
• Lipids
• Proteins
• Color
changes indicated the presence of
each macromolecule except lipids.
•Simple Carbohydrates
• Benedicts
reagent was added to a
glucose solution.
• The solution was heated.
• Color should have changed from a light,
clear blue to a orange-yellow color.
•Complex Carbohydrates (Starch)
IKI was the indicator used in a starch solution.
• IKI turns this solution
into a dark
blue/black color.
•
•Proteins
Buirets reagent was the indicator for
this test.
• It was added to a protein solution.
• The presence of proteins was
indicated by changing colors from
clear blue to a violet color.
•
a
•Lipids
•
•
•
•
No indicator was utilized in this activity.
On a paper bag, water and oil were dropped in equal
amounts.
Results were observed.
An expanded, greasy spot indicated oil.