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Chapter 5 - Energy Pathways Review
1. You must know ATP’s function as an energy molecule. Specifically be able to discuss:
• how many phosphate groups would need to be removed from ATP to create the following molecules:
Adenosine, AMP, and ADP.
Remove 1 for ADP, 2 for AMP and 3 for adenosine
• how energy is released when a molecule of ATP loses one or more of its phosphate groups.
Net energy is released when a water molecule is used to hydrolyze the reaction.
ADP + water → ADP + Pi + energy
• how cells make ATP from ADP + P.
Cells create ATP from both substrate level phosphorylation and oxidative phosphorylation. (review handout
comparing both processes)
2. How does energy storage in ATP differ from that in NADH?
In ATP, energy is stored in phosphate bonds; in NADH, the energy is stored in the bond with the hydrogen
atom.
3. How do cells couple energy storage in ATP and NADH?
Energy stored in the NADH is released when it is oxidized. This energy will be used to fuel the production
of ATP.
4. If a molecule of NADH can store more energy than a molecule of ATP, why is ATP used as the universal energy
currency of cells?
ATP is an efficient and relatively simply biosynthesised molecule that can fulfill multiple biochemical roles.
Cells do have alternative energy carriers, some with more specialized roles, however ATP is ubiquitous
throughout our cells and inter-cellular spaces. There isn't a wealth of resources explaining why ATP is any
better than other compounds, however there is plenty of reasons why the phosphates are required.
5. The following reaction shows the burning of methane. In the process, _______ is oxidized and _______ is
reduced.
CH4 + 2 O2 → CO2 + 2 H2O
a.
b.
c.
d.
e.
H2O; CO2
O2; CH4
CO2; H2O
CH4; O2
CH4; CO2
6. A proton gradient across a membrane
a. is only used by eukaryotes for energy metabolism.
b. couples the oxidation of NADH to the synthesis of ATP.
c. couples the reduction of NADH to the synthesis of ADP.
d. can only be established if the pH inside the membrane is greater than 10.
e. None of the above
7. Draw a mitochondria including its membrane, then, label where each of the following occurs:
• The chemical reactions of glycolysis – outside the mitochondria
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•
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The chemical reactions of pyruvate oxidation and the citric acid cycle – matrix of mitochondria
The chemical reactions of the electron transport chain – across inner mitochondrial membrane
Answer the following questions:
 At which of these three intracellular sites is hydrogen oxidized to yield water?
Inner mitochondrial membrane
 At which site is CO2 produced?
Mitochondrial matrix
 Can any of these processes occur in the absence of oxygen?
Glycolysis is the only thing that can occur without oxygen
8. The oxidation of pyruvate is a multistep process. What does it accomplish? (Select all that apply.)
a. It forms a 3-carbon molecule known as acetyl-CoA.
b. It begins with oxaloacetate.
c. It binds a 2-carbon acetate group to coenzyme A.
d. It produces ATP.
e. It is catalyzed by pyruvate dehydrogenase.
9. How is the electron transport chain is coupled to chemiosmosis. Specifically consider:
• The roles of coenzymes NADH and FADH2 . – these provide the energy to create the gradient that exists
for chemiosmosis
• The importance of the proton gradient to ATP synthase.
The large proton gradient and subsequent flow of H+ down the gradient provides the energy to turn the
ATP synthase molecule and create ATP.
What mutations or changes in the function/structure of either ATP synthase, or any of the other cell respiration
participants, would result in the inhibition or decrease in the synthesis of ATP?
DON’T WORRY ABOUT THIS ONE
10. Compare and contrast lactic acid fermentation and alcoholic fermentation by answering the following
questions:
1. What molecule results from lactic acid fermentation of pyruvate?
Lactic Acid (Lactate)
2. What molecule ultimately results from alcoholic fermentation of pyruvate?
Ethyl Alcohol
3. Is oxygen required for lactic acid fermentation?
No
4. Is it required for alcoholic fermentation?
No
5. Can oxygen inhibit or reduce the need for fermentation?
Yes – in the presence of oxygen the cell will perform cellular respiration which results in a greater
amount of ATP per glucose molecule.
6. Where in a cell does fermentation typically occur?
In the cytosol
7. Are there any energetic advantages of lactic acid fermentation over alcoholic fermentation?
No
8. Name a eukaryote that uses lactic acid fermentation.
Lactobacillus
9. Name a eukaryote that uses alcoholic fermentation.
Yeast
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11. Which statement about anaerobic metabolism in humans is false?
a. It builds up lactic acid (lactate) in skeletal muscles.
b. It can result in muscle pain because of the buildup of lactate.
c. It is reversible, and the accumulated lactate can be fully metabolized once oxygen is available.
d. It takes place in the cell cytoplasm.
e. It generates CO2.
12. A carbon atom in a protein from a slice of tofu that you ate could become incorporated into:
a. a lipid molecule that you store in a fat cell.
b. a strand of DNA that a connective tissue cell synthesizes for cell division.
c. a molecule of glucose, by the process known as gluconeogenesis.
d. a protein molecule in a muscle cell.
e. Any of the above
13. Chlorophyll molecules in green plants absorb what colors of light? (Select all that apply.)
a. Red
b. Yellow
c. Green
d. Blue
e. Ultraviolet
14. Oxygen generated during photosynthesis comes from
a. atmospheric CO2.
b. water in the plant’s cells.
c. chlorophyll molecules.
d. glucose.
e. oxygen atoms bound together using light energy.
15. Answer the following questions:
• What are the molecular products of the light reactions, and how are they produced?
NADPH (thorough reduction reaction), ATP (through oxidative phosphorylation) & O2 (through
oxidation)
• What is the main product of the carbon-fixation reactions, and how is it produced?
G3P which is a 3 carbon sugar produced through carbon fixation & reduction reactions
• In eukaryotes, such as green plants, where in a cell do the light reactions occur? Where do the
carbon-fixation reactions occur?
Light reactions – thylakoid memebrane C-fixation – stroma
• Where does the CO2 that is an input to the Calvin cycle come from?
The atmosphere
• Is energy consumed or produced in the Calvin cycle?
Consumed
• Why must ribulose bisphosphate (RuBP) be regenerated for the Calvin cycle to continue?
It is what is involved in the carbon fixation which is the first step in the cycle
16. Which of the following statements are correct?
a. An autotroph cannot survive without an external source of carbohydrate, whereas a heterotroph
can. – FALSE
b. An autotroph can survive without an external source of carbohydrate, whereas a heterotroph
cannot. - TRUE
c. Microscopic algae in the ocean are examples of autotrophs, and the planktonic organisms that
consume them are examples of heterotrophs. TRUE
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d. Microscopic algae in the ocean are examples of heterotrophs, and the planktonic organisms that
consume them are examples of autotrophs. FALSE
e. None are correct.
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