05

Biology 111B
Study Questions 5

METABOLISM

RESPIRATION AND FERMENTATION

1. What do the following terms mean?

oxidation
reduction

oxidizing agent

reducing agent

2. What is the summary reaction for cellular respiration?

3. What is the "goal" or purpose of cellular respiration?

4. What are the main reactions of cellular respiration? Where in the cell does each take place?

5. What are the functions of NAD⁺ and FAD?

6. At what stage is oxygen used? What happens if oxygen is not available? What are the relative yields of ATP in the presence and absence of oxygen?

7. What is chemiosmosis? Why is it important? What membrane acts in this process, and how does it function?

8. What are the possible products of fermentation? Why does a cell make these products? How much ATP does a cell make by fermentation?

9. Which of the following is in its reduced state? CIRCLE ALL CORRECT ANSWERS

a. NAD⁺
b. FAD

c. molecular oxygen (0₂)

d. oxygen in water

e. carbons in carbon dioxide

10. When molecules are broken apart in respiration. CIRCLE ALL CORRECT ANSWERS

a. the heat produced is used to drive biological reactions.
b. the oxygen in the compounds broken apart is used an as energy source.

c. the energy released in respiration is channeled into molecules of ATP.

d. NADH is reduced to form NAD⁺.

e. CO₂ is released as a waste product.

11. Which molecules do each of the following parts of cellular respiration PRODUCE?

glycolysis _______

A. O₂

fermentation ______________

B. NADH

Krebs cycle _____________

C. ATP

respiratory electron transport ____________

D. NAD⁺

12. Pyruvate is the last product of glycolysis. Which statement(s) below are true?

a. There is more energy in 6 molecules of CO₂ than in 2 molecules of pyruvate.
b. There is more energy in pyruvate than in lactic acid.

c. There is more energy in 1 molecule of glucose than in 2 molecules of pyruvate

d. There is more energy in 1 NADH than in 1 ATP

13. What is the correct sequence of the following compounds, in order, from the one that contains the most energy to the one that contains the least energy?

a. NADH -> ATP -> glucose -> pyruvate -> lactic acid
b. ATP -> NADH -> pyruvate -> lactic acid -> glucose

c. glucose -> pyruvate -> lactic acid -> NADH -> ATP

d. glucose -> lactic acid -> pyruvate -> NADH -> ATP

e. pyruvate -> glucose -> lactic acid -> ATP -> NADH

14. The transformation of pyruvate to ethanol doesn't provide a yeast cell with any energy. One reason that cells do the reaction is to get rid of pyruvate that would be toxic in high concentrations. But yeast cells would have to carry out the formation of ethanol even if pyruvate were harmless. Why?

a. because the cell needs ethanol to survive
b. because the cell needs NAD⁺ to continue to do glycolysis

c. because the cell needs NADH to continue to do glycolysis

d. because the cell needs O₂ to survive

e. because people need ethanol to make beer and wine

15. Why can prokaryotes extract about 38 ATPs from a molecule of glucose, whereas most eukaryotic cells can extract only about 36 ATPs?

16. DNP (dinitrophenol) is a metabolic poison that makes membranes leaky to hydrogen ions. Symptoms of DNP poisoning include lack of energy, weight loss, and excessive sweating. Why does DNP cause these symptoms?

17. Yeast can carry out metabolism of glucose either in the presence of O₂ or in the absence of O₂. However, in the absence of O₂, yeast use glucose at a much faster rate than in the presence of O₂. Explain this observation.

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18. White snakeroot is a toxic plant sometimes consumed by dairy cattle. The cattle concentrate the toxin in their milk and can pass it along to humans, sometimes with fatal consequences. The symptoms of poisoning are intensified by vigorous exercise. Knowing that the toxin interferes with the conversion of lactic acid to pyruvate in the liver, how can you explain the effect of exercise?

19. Normally, a solution of isolated mitochondria only make ATP when supplied with pyruvate. However, isolated mitochondria will also make ATP if they are placed in an acid solution. Why? What does this phenomenon tell you about the mitochondrial outer membrane?

PHOTOSYNTHESIS

20. What is the summary reaction for photosynthesis?

21. What is the "goal" or purpose of photosynthesis?

22. What are the main reactions of photosynthesis? Where in the cell does each take place? What is the "goal" or purpose of each?

23. What is the green photosynthetic pigment? Why is it green in color? How does it "capture" light?

24. What is rubisco and what function does it carry out?

25. What is the problem rubisco has when oxygen concentrations get too high? Why do dry conditions cause oxygen concentrations to build up? Why do hot conditions cause oxygen concentrations to build up? Why (evolutionarily) does rubisco have this problem?

26. What solution have tropical plants evolved to deal with rubisco's problem under hot conditions? What solution have desert plants evolved to deal with ribisco's problem under dry conditions?

28. A solution of isolated chlorophyll molecules fluoresces (glows red) when illuminated. A solution of isolated chloroplasts fluoresces when illuminated only if all CO₂ is removed from the atmosphere in the flask. Explain why the chloroplast solution fluoresces only in the absence of CO₂.

29. The rate of the light-dependent reactions can be determined by measuring the rate of O₂ formation by a solution of isolated chloroplasts. Adding bicarbonate, a source for dissolved CO₂, increases the rate at which the light-dependent reactions proceed. If CO₂ is used in the Calvin cycle and O₂ is produced in the light-dependent reactions, why should adding CO₂ increase the rate of O₂ production?

30. If the stroma of a chloroplast could experimentally be made more acidic than it naturally is, would more or less ATP be formed? Why?

Now that you've reviewed photosynthesis, go on to the metabolism questions that integrate/compare/constrast respiration, fermentation, and photosynthesis.

METABOLISM (Respiration, photosynthesis, fermentation ...)

31. In the blank next to each process, write an R if it occurs in respiration and/or a P if it occurs in photosynthesis. Write an N if the process occurs in neither respiration nor photosynthesis.

___ Chemiosmotic synthesis of ATP

___ Reduction of electron carriers

___ Reduction of oxygen

___ Oxidation of water

___ Reduction of CO₂

___ Oxidation of glucose

32. Which of the following descriptions on the left match with the terms on the right? Be as specific as possible.

___ 3C compound product of glycolysis

A. ATP

___ site of glycolysis in eukaryotes

B. ADP

___ site of NADH oxidation

C. H₂O

___ compound that initially oxidizes glucose

D. cytosol

___ site of O₂ use

E. thylakoid membrane

___ site of O₂ formation

F. NAD⁺

___ compound oxidized by chlorophyll

G. NADH

___ site of [H⁺] build-up in photosynthesis

H. interior of thylakoid

___ sites of glucose synthesis

I. mitochondrial electron transport chain

J. Krebs cycle

K. intermembrane space

L. stroma

M. pyruvate

N. NADP⁺

33. Why does a photosynthetic plant first make glucose and then break it down in cellular respiration? Why not just use ATP directly?

34. If a plant is growing, which reaction is going faster, photosynthesis or respiration?

glycolysis _______	A. O₂
fermentation ______________	B. NADH
Krebs cycle _____________	C. ATP
respiratory electron transport ____________	D. NAD⁺

___ Chemiosmotic synthesis of ATP	___ Reduction of electron carriers
___ Reduction of oxygen	___ Oxidation of water
___ Reduction of CO₂	___ Oxidation of glucose

___ 3C compound product of glycolysis	A. ATP
___ site of glycolysis in eukaryotes	B. ADP
___ site of NADH oxidation	C. H₂O
___ compound that initially oxidizes glucose	D. cytosol
___ site of O₂ use	E. thylakoid membrane
___ site of O₂ formation	F. NAD⁺
___ compound oxidized by chlorophyll	G. NADH
___ site of [H⁺] build-up in photosynthesis	H. interior of thylakoid
___ sites of glucose synthesis	I. mitochondrial electron transport chain
	J. Krebs cycle
	K. intermembrane space
	L. stroma
	M. pyruvate
	N. NADP⁺