Microscope - Exercise 1
1. In the diameter of field of view of a light microscope at 40X magnification is 6,000
micrometer (um), what would be the field of view at 400X magnification?
40 x 6000 = 600 um
400
2. An elodea cell was found occupying 40% of field of view’s diameter at 400X magnification.
At this magnification the field of view of the microscope is 200 micrometer. What is the size of
the elodea cell? Remember this is a gesstimate percent of the diameter of the field of view is
occupied by the object (image).
40 = .4
100
.4 x 200 = 80 um
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Organic Molecules of Life - Exercise 2
1. You are given two unlabeled containers and told that one of them contains a solution of pure
glucose and the other contains a solution of pure maltose, a disaccharide. How can you identify
the content of the bottle by performing chemical assays? You can perform the Bendicts and
Barfoed’s assay to see what reactions are positive. Maltose will only be positive in the
Bendcit’s assay due to the pH (7) environment. And, if you perform the Barfoed’s assay
and get a negative result, then you know you got Benedict’s assay for maltose. For glucose
you get a positive reaction for the Bendict’s assay and a negative result for Barfoed’s assay.
2. What is a monosaccharide? Why all monosaccharides and most disaccharides are reducing
sugars? A monosaccharide is a simple sugar that contain a carbonyl group. They can
accept (gain) the Cu ion under acceptable pH levels, for instance, pH 7.
3. In solution, chain and ring forms of glucose molecules exist in equilibrium. Explain this
statement? Solutions of these sugars will contain both the chain and ring form in
equilibrium, and each of the forms can freely convert in to the alternative form under
favorable chemical conditions.
4. Both fructose and glucose are reducing sugars. When these two simple sugars become
chemically bonded, a disaccharide, sucrose, is formed. Why sucrose is not a reducing
disaccharide? Sucrose always has rings, so it’s a non-reducing sugar. You could put
sucrose into any solution, and it’s the same thing as throwing water, so nothing would
change.
5. What is the active ingredient in Benedict’s solution? Cu
6. What is the active ingredient in Barfoed’s solution? Cu
7. The above answer identify that both Benedict’s and Barfoed’s solutions are made from the
same ingredient. Why are their reaction capabilities different? pH is different, so some
carbohydrates are able to receive electrons form Cu based on the environment, so in this
case its pH.
8. Write three names of monosaccharides.
Glucose, Fructose, & Galactose
9. Write two names of reducing disaccharides.
Lactose & Maltose
10. What is the difference between reducing disaccharide and non-reducing disaccharides? The
environment, in our case, the pH was the factor. Under alkaline conditions a disaccharide
could gain an electron from the copper ion, but in an acidic environment (pH 4.5) the
disaccharide can’t accept the electron from the copper ion.
11. What are three names of polysaccharides.
Starch, Glycogen, & Cellulose
a. Sucrose
b. Maltose
c. Starch
d. Glucose
e. Egg albumin
12. This substance gives a negative Benedict’s assay, a negative Barfoed’s assay, a positive
iodine assay and a negative Biuret assay. C - Starch
13. This substance gives a positive Benedict’s assay, a positive Barfoed’s assay, a negative
iodine assay, and a negative Biuret assay. D - Glucose
14. This substance gives a positive Benedict’s assay, a negative Barfoed’s assay, a negative
iodine assay, and a negative Biuret assay. B - Maltose
15. This substance is positive in Biuret assay and negative in all other assays.
E - Egg albumin
16. All test (Bendict’s, Barfoed’s, iodine, and Biuret) on the substance came negative.
A - Sucrose
17. Benedict’s assay is for reducing sugars Positive reaction for Benedict’s assay produces red
color.
18. Barfoed’s assay distinguishes between monosaccharide and reducing sugar.
19. A protein solution can be identified by performing the Biuret assay.
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Enzymes - Exercise 3
1. What is an Enzyme: A protein catalyst that speeds up a reaction without getting consume
in a chemical reaction. It lowers the activation energy barrier too.
2. Enzymes increase the rate of a reaction by.
A.
B.
C.
D.
Decreasing the requirement of activation energy.
Providing the activation energy to the reaction.
Both A & B
None of the above.
3. Do you expect an enzyme to be active at 0o C. Why? Yes, the enzyme is still active but is
working at slower rates.
4. If you keep an enzyme at 0o C for an extended period of time and then bring back to its
optimum temperature, would you expect the enzyme to be active? Explain. Yes, because the
enzyme is not denatured at 0o C, it just works at a slow rate, but when your increase the
temperature to its optimum temperature, the enzyme will work.
5. Name at least three physical and chemical factors that affect enzyme’s activity (denature a
protein/enzyme)?
Temperature, pH, Concentration (salt), Cofactors, & Inhibitors
6. All enzymes function optimally at PH 7.4
True or False
7. What is the importance of enzyme in living systems? Enzymes speed up reaction
8. The optimum temperature of our enzyme was 35 degrees Celsius.
9. In general, as temperature increases, the rate of enzyme activity (increases/decreases) up to a
certain point called the optimum temperature, at which activity is at a maximum. After this
point, activity (increasing/decreases). At very high temperatures we see (high/low/no) activity
because the enzyme is denatured.
10. Draw a curve representing enzyme activity as it changes with temperature. Label the point
of the optimum temperature.
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Diffusion & Osmosis - Exercice 4
1. Define osmosis: The diffusion of water (or some other solvent) across a selective
permeable membrane hyp, hyper, iso. Special case of diffusion of water (Higher
concentration to lower concentration).
2. How does dialysis differs from osmosis? In dialysis water has to go through a selectively
permeable membrane that’s specific to a substance size, but in osmosis its concentration of
gas, molecules, water from higher to lower concentration and water is the solvent moving,
and only water.
3. If a 50% sucrose solution is separated from a 20% sucrose solution by a membrane that does
not allow sucrose to pass through, in which direction the movement of water will take place.
a)
b)
c)
d)
There will be no net movement of water
Water will move into 50% sucrose solution from 20% sucrose solution.
Water will move into 20% sucrose solution from 50% sucrose solution.
In this case only dialysis will take place.
4. A dialysis bag, permeable to water and not permeable to sucrose, filled with 30% sucrose
solution and was placed in a beaker full of water. The bag’s initial weight was 15g, and after 15
minutes it became 17g. Calculate the percent change in weight of the dialysis bag.
17 - 15 X 100 = 13%
15
5. A dialysis bag, permeable to water and not permeable to sucrose, filled with water was place
30% sucrose solution. The bag’s initial weight was 15g, and after 15 minutes it became 17g.
Calculate the percent change in weight of the dialysis bag. After 45 minutes it was found the
same bag weighted 20 g. What Is the cumulative percent change in weight of the bag at that
point?
17 - 15 X 100 = 13%
20 - 15 X 100 = 33.33%
15
15
6. Four dialysis tubing bags were filled with the following solutions listed on the table below
and closed off. Each of the bags were placed in separate beakers that contained 40%
sucrose. The bags were weight every 15 minutes for 45 minutes. The dialysis tubing that was
used in permeable to water but not to sucrose.
BAG
SOLUTION IN BAG
Bag # 1
Bag # 2
Bag # 3
Bag # 4
Contains 0% sucrose
Contains 40% sucrose
Contains 60% sucrose
Contains 20% sucrose
SOLUTION IN THE BEAKER
40% Sucrose
40% Sucrose
40% Sucrose
40% Sucrose
In the table below, describe the expected weight changes, if an , for each of the four bags after 45
minutes. Answer by saying one of the following. The bag will gain weight slowly; The bag will
gain weight rapidly; The bag will lose weight slowly; The bag will lose weight rapidly. The bag
will not change in weight.
State whether the bag is hypertonic, isotonic, or hypotonic to the beaker.
Bag
General Weight Changes
Bag # 1
The bag will lose weight
quickly
The bag will not change in
weight, but there’s movement.
Bag # 2
Hyper, Isotonic,
Hypo
Hypertonic
Isotonic
Bag # 3
The bag will gain weight
Hypotonic
Bag # 4
The bag will lose weight
slowly
Hypertonic
7. Iodine diffused into the starch as seen by the dark blue color (inside/outside) of the bag.
8. This happens because iodine has a smaller molecular molecules than starch.
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Cellular Respiration Gerbil Metabolism - Exercice 5
1. What was the name of the instrument that we used in the cellular respiration lab? Manometer
2. What did this instrument measure? Amount of oxygen consumed
3. During the experiment, the fluid moved (towards/away from) the gerbil because of changes in
gas or air pressure as the animal respired.
4. An organism whose body temperature changes with the outside environment is called an
ectotherm or poikilotherm Its metabolic rate (increase/decreases) as temperature increases.
5. An organism who is able to maintain a stable internal body temperature regardless of the
environmental temperature is called an endotherm or homeotherm It’s metabolic rate
(increases/decreases) as temperature increases.
6. Which of the following is homoeothermic?
a. Fish
b. Reptiles
c. Grass hopper
d. Chicken
e. Paramecium
7. In the experiment you did on cellular respiration, the soda lime in the gerbil’s jar:
a. Provided oxygen for the gerbil.
b. Absorbed oxygen given off by the gerbil
c. Absorbed CO2 given off by the gerbil.
d. Provided CO2 to the gerbil.
e. Absorbed moister to keep the gerbil dry.
8. In the experiment, you determined metabolic rate by measuring:
a. Oxygen production by the gerbil
b. The body temperature of the gerbil
c. Oxygen consumption of the gerbil
d. The rate at which the gerbil moved.
9. What is the relationship between the body size and metabolic rate? The bigger you are, the
slower your metabolic rate will be and vice versa.
10. In case of fish or frog, what will happen to the metabolism of the animal if the surrounding
temperature is gradually decreased? Their metabolism will decrease too because there both
cold blooded animals. This is a direct relationship.
11. What is fermentation? What is the advantage of fermentation? What is the disadvantage of
it? Ethanol + CO2 are produced by fermentation & no oxygen is required.
12. Calculate the metabolic rate of a gerbil that weights 120 g and consumes 4.2 ml of oxygen in 6
minutes.
4.2/6 x 60 = 42
42/120
.35 ml/hr/g
13. Calculate the metabolic rate of a gerbil that weights 100 gm and consumes 2 ml of oxygen in 3
minutes.
2/3 x 60 = 40
40/100
.4 ml/hr/g
14. A 50 gram gerbil who consumes 5 mL of oxygen in 3 minutes would have a metabolic rate of?
5/3 x 60 = 100
100/50
2 ml/hr/g
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Photosynthesis - Exercise 6
1. What type of energy is used in this reaction? Sunlight (light intensity - wattage)
2. What absorbs that energy? Chlorophyll
3. A spectrophotometer measures? Absorption of light wavelengths
4. Which colors of light absorb the most pigment? Violet/blue and a little red.
5. Which colors of light will be most effective for photosynthesis? Violet/blue some red.
6. This is the absorption spectrum for which pigment? Chlorophyll
7.
a)
b)
c)
Paper chromatography separators pigments on the bases of which 3 properties?
Molecular weight
Solubility in the solvent
Affinity for the chromatography paper
8. Labe the pigments on the chromatograph:
9. A paper chromatography was done using acetone as a solvent. At the end of the
chromatography it was found that the solvent traveled 20 cm and a pigment molecule traveled 17
cm from its origin. Calculate the Rf value of the pigment molecule? 17/20 = .85 cm
10. Which pigment has the second highest molecular weight? Chlorophyll-a
11. Which pigment is the most soluble, lowest molecular weight, and has a low affinity?
Carotenes
12. Which pigment has the highest affinity and molecular weight? Chlorophyll-b
13. Complete the following table and plot a graph with the data (Wattage: Y axis Vs. rate on
photosynthesis X axis)
14. Why does this graph make sense? As wattage increases more oxygen is being release by
the plant, but at a certain point photosynthesis has to stop because a plant simply just give
up oxygen for infinity of time, that’s why the graph is going down, or maybe the plant is
small in structure.