Biol 131
Question Bank
Harvesting Energy
1. Which of these answers place the stages of glucose catabolism in their correct sequence?
A.
B.
C.
D.
glycolysis  Pyruvate  Acetyl CoA  Electron Transport Chain  Krebs Cycle
glycolysis  Pyruvate  Acetyl CoA  Krebs Cycle  Electron Transport Chain
glycolysis  Acetyl CoA  Pyruvate  Electron Transport Chain  Krebs Cycle
glycolysis  Acetyl CoA  Pyruvate  Krebs Cycle  Electron Transport Chain
2. In either the diagram of the cell or the enlarged diagram of a
mitochondrion, indicate where each of these processes occurs.
1. Glycolysis
2. Krebs cycle
3. Pyruvate dehydrogenase reaction
4. Electron transport chain
3. What is the advantage to the cell of the gradual oxidation of glucose during cellular respiration compared
with its combustion to CO2 and H2O in a single step?
A.
B.
C.
D.
E.
more free energy is released for a given amount of glucose oxidized.
no energy is lost as heat.
energy can be retained in a usable form.
more CO2 is produced for a given amount of glucose oxidized.
less O2 is required for a given amount of glucose oxidized.
4. These are the processes by which your body converts a piece of toast you had for breakfast into ATP:
1. Hydrolysis of starch to glucose
2. Glycolysis
3. Conversion of pyruvate to acetyl CoA
4. Krebs cycle
5. Chemiosmotic phosphorylation
Which stage(s), if any:
A. produces the most ATP
_________________
B. use O2 that you breathe
_________________
C. produce lactic acid
_________________
D. produce NADH
_________________
E. produce CO2
_________________
Biol 131
Question Bank
Harvesting Energy
Page 1
5. A piece of paper (composed of many glucose molecules in the form of cellulose) can be ignited with a
match, starting a combustion reaction.
A. How is initiation of glucose catabolism similar to igniting a piece of paper? _________
______________________________________________________________________
B. What are the end products of the combustion of glucose? _______, _______, _______
C. What are the end products of the catabolism of glucose? _______, _______, _______
D. What are the similarities and differences in the end products of these two processes?
6. The cytoplasm of red blood cells (RBC) has a very simple structure, lacking a nucleus and other internal
organelles, and containing enormous quantities of hemoglobin. In clinical labs, the glucose levels in the
serum of a blood sample are measured to diagnose diabetes and other metabolic disorders, but often the
analysis cannot be performed for an hour or more after the blood is drawn. During that time, RBCs will
metabolize glucose in the serum, altering both serum glucose level and acidifying the pH. This problem is
circumvented by collecting the blood into sample vials that contain Na-fluoride.
A. Through what pathways is glucose metabolized by RBCs, and why does it lead to acidification of the
serum sample?
B. Considering the cellular structure of RBCs, why is it not surprising that they do not perform Krebs cycle
and electron transport pathways?
C. Why does this make sense with the function of RBCs?
7. Yeast cells can grow aerobically or anaerobically. In the absence of oxygen, yeast cells consume glucose at
a high, steady rate. When oxygen is added, glucose consumption drops precipitously and is then maintained
at the lower rate. Why do yeast cells consume glucose at a high rate in the absence of oxygen and at a low
rate in its presence?
8. Draw a line connecting each form of energy interconversion with the correct example
Light to chemical
Muscle contraction
Chemical to light
Internal warming of our bodies
Chemical to chemical
ATP synthesis from glucose
Chemical to kinetic
Photosynthesis
Chemical to electrical
Firefly bioluminescence
Chemical to heat
Nerve cell impulse
Biol 131
Question Bank
Harvesting Energy
Page 2
9. Acetyl-CoA serves as an important metabolic branch point. The acetyl groups that it carries can be used for
ATP production through the Krebs cycle and electron transport, or energy storage through fatty acid
synthesis.
A. If a person has a high carbohydrate diet and a sedentary lifestyle, do you think that carbohydrates
will be processed through the Krebs cycle and chemiosmotic phosphorylation into ATP, or into fatty
acids? ________________________________
Which molecule is the ‘branch point’ between aerobic respiration of carbohydrates and fatty acid
synthesis? _________________________________
B. How many carbons does an acetyl group possess? Considering this, would you expect most fatty
acids to have an even or odd number of carbons? _____________________
C. What type of energy storage molecule contains fatty acids, and accumulates in the body’s adipose
tissue? ____________________________
D. When proteins are used as an energy source, they are broken down first into molecules that feed into
the Krebs cycle below acetyl-CoA. Why might a high protein diet often lead to dangerously high
ammonia (NH3) levels in the blood, but not fat production?
10. Traditionally, beer is brewed through the fermentation of barley malt. Malt is produced by allowing barley
seeds to germinate for a short period of time, allowing the starch of the grain to be broken down into smaller
carbohydrate subunits. Germination is terminated by roasting of the grain (which also contributes flavor).
Carbohydrates are then extracted and provided to yeast cells for fermentation, yielding the production of
ethanol.
A. Do the yeast cells or the plant cells (while they are alive) derive more energy from glucose
catabolism? Why? _______________________________________________________
______________________________________________________________________
______________________________________________________________________
B. What is the net yield of ATP by the yeast cells from each molecule of glucose fermented?
__________________________
C. Considering the net yield of ATP from glycolysis and fermentation, and using a value of 7.3
Kcal/mol / ATP, what is the total energy yield per glucose? ________________
11. In this diagram of the mitochondrial ATP synthase:
A. Draw in H+ ions to show the proper orientation
gradient,
of the
B. Indicate the direction of flow of H+ ions through
transporter, and
the
C. Indicate where ATP synthesis will occur.
Biol 131
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Harvesting Energy
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12. This question addresses the energy yield from cellular respiration.
A. Per molecule, the ATP yield is:
___ from NADH produced in the mitochondria.
___ from NADH produced from glycolysis in eukaryotes.
___ from FADH.
B. Complete this diagram for a single glucose molecule. Show the
number of ATP, NADH, and FADH produced by each stage of
cellular respiration, and the amounts of ATP then produced through
electron transport.
in eukaryotes
13. A species of bacteria that uses aerobic respiration produces 38 moles of ATP from each mole of glucose.
Burning a mole of glucose releases about 686 kcal. If a mole of ATP contains 7.3 kcal of energy:
A. Calculate the efficiency of these bacteria in converting the chemical energy in glucose to chemical
energy in ATP? (Show your work) Efficiency = _______________%
B. Why do you think a bacterium would be able to get 38 ATP out of each glucose while we generally
expect eukaryotic cells to produce 36 ATP per glucose that goes through cellular respiration?
C. As described in the book, the actual yields of ATP from electron transport are 2.5 ATP/NADH and
1.5 ATP/FADH instead of the theoretical values of 3 and 2, respectively. Why?
Biol 131
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Harvesting Energy
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14. The inner mitochondrial membrane is relatively impermeable to protons. If otherwise normally functioning
mitochondria were exposed to a chemical that causes the membrane to become freely permeable to protons,
all of the following processes would occur. For each one, explain why.
A. ATP synthesis would cease. _______________________________________________
______________________________________________________________________
B. NADH would continue to be converted to NAD. ______________________________
______________________________________________________________________
C. CO2 would continue to be produced. ________________________________________
______________________________________________________________________
D. O2 consumption would continue to occur. ____________________________________
______________________________________________________________________
E. More energy would be released as heat. _____________________________________
______________________________________________________________________
15. Place the following processes in the correct order:
____ ADP and Pi combine to form ATP
____ e- move between electron transport
proteins
____ H+ passes through ATP synthase
____ H+ pumped into intermembrane
space
____ NADH donates eThe diagram to the right shows the flow of
electrons through the mitochondrial etransport chain. Complete the diagram as
follows:
A. Label the molecular interconversions occurring on complexes A and B.
B. Draw arrows to show the pumping of H+ ions by the transport protein complexes
C. Label where the H+ concentration will be high and low.
D. Add the ATP synthase and show the direction of H+ flow through it and diagram the ATP synthesis
reaction.
Labeling must be done clearly and unambiguously.
Biol 131
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Harvesting Energy
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16. Suppose you isolated mitochondria and put them into a solution that
includes all the compounds that the mitochondria might need to
function normally including ADP, Pi, ATP, NADH and NAD+. These
mitochondria are then placed into three different solutions, as shown
in the diagram. The control is a solution of pH 7.7. Because of the
properties of the inner and outer mitochondrial membranes, the
intermembrane space also assumes this pH, but the matrix remains at
its normal pH of 8.3.
1. In Experiment 2, the outer solution has a pH of 6.5.
A. How would lowering the pH of the solution to 6.5 affect the
H+ gradient?
B. Explain why production of ATP would be faster in Exp 2 than
in the control.
C. Explain why the rate of electron transport would also be
slowed somewhat in Exp 2.
2. In Experiment 3, the solution also has a pH of 6.5 but also
contains a drug that causes H+ ions to freely flow across the inner
mitochondrial membrane.
A. What would be the effect of this drug on the H+ gradient?
B. Explain why production of ATP would be slower in Exp 3 than in Exp 2.
C. Explain why the drug does not inhibit electron transport in Exp 3.
D. Based upon your above answers, what would be the expected effect of this drug on O2 usage in the
mitochondria?
Biol 131
Question Bank
Harvesting Energy
Page 6