Carbohydrate metabolism-Practice questions

1) Which of these enzyme reactions is not irreversible in glycolysis?

a) Hexokinase

b) Glucokinase

c) 3-phosphoglycerate kinase

d) Phosphofructokinase-1

e) Pyruvate kinase

2) Which out of the following statements is not true about aerobic glycolysis?

a) The rate-limiting enzyme is phosphofructokinase-1 which converts fructose-6- phosphate to fructose-1,6-bisphosphate

b) The pathway is activated allosterically by fructose-2,6-bisphosphate and AMP

c) The pathway takes place in mitochondria of every cell

d) The pathway produces Pyruvate and NADH

e) The pathway begins with glucokinase or hexokinase.

3) The first enzyme in the glycolytic pathway in muscle-

a) Is glucokinase

b) Uses ATP and glucose-6-phosphate as substrates

c) Produces glucose-1-phosphate and ADP

d) Is reversible

e) Is an isozyme of glucokinase found in the liver

4) Phosphoglycerate kinase functions in carbohydrate metabolism to produce ATP via:

a)  Oxidative phosphorylation.

b) Substrate-level phosphorylation.

c) Oxidative decarboxylation.

d) Phosphorolysis

e) Oxidative deamination

5).The enzyme that transfers a phosphate group to fructose-6-phosphate in glycolysis-

a) Is called phosphofructokinase-2

b) Catalyzes a reversible reaction

c) Produces fructose-2,6-bisphosphate as a product

d) Is the rate-limiting enzyme for glycolysis

e) Produces ATP as a product

6).The enzyme that produces NADH from a triose phosphate in the glycolytic pathway

a) Uses NAD⁺and dihydroxyacetone phosphate as substrates

b)Produces 3-phosphoglycerate and NADH

c) Is reversible

d) Is called 3-phosphoglycerate kinase

e) Uses FADH₂and glyceraldehyde-3-phosphate as substrates

7).The first substrate-level phosphorylation in glycolysis

a) Produces 3-phosphoglycerate as a product

b) Produces ADP from AMP

c) Is called glyceraldehyde-3-phosphate dehydrogenase

d) Is called phosphofructokinase

e) Is irreversible.

8).The enzyme that catalyzes the second substrate-level phosphorylation of glycolysis:

a) Is called phosphoglyceromutase

b) Produces lactate as a product

c)Uses phosphoenolpyruvate as a substrate

d) Is found in the mitochondria

e) Is reversible

9).Which of the following statements about the LDH reaction is FALSE?

a) The enzyme converts pyruvate to lactate

b)The enzyme converts NADH to NAD⁺

c) The reaction is reversible

d) It is the last enzyme reaction in anaerobic glycolysis

e) The enzyme is found in the liver but not in muscle

10).The two major factors determining whether a cell oxidizes glucose by aerobic glycolysis or by anaerobic glycolysis are:

a) FADH₂and the number of mitochondria

b) NADH and the ATP/ADP ratio

c) Ca⁺⁺and AMP

d) Oxygen pressure and the number of mitochondria

e) Ca⁺⁺and NADH

11). When glucose is converted to lactate by anaerobic glycolysis, the equivalent of ________ ATPs are derived.  When glucose is completely oxidized to CO₂ by glycolysis, Pyruvate dehydrogenase, and the TCA cycle, the equivalent of _______ ATPs are derived.

a) 7;  20

b) 2;  32

c) 7;  32

d)2;  12

e) 7;  25

12). When one molecule of glucose is oxidized to 2 molecules of lactate during anaerobic glycolysis, all of the following are correct EXCEPT:

a) One molecule of ATP is used by the phosphofructokinase-1 reaction

b)One molecule of ATP is used by either the glucokinase or hexokinase reaction

c) Two molecules of ATP are produced by the phosphoglycerate kinase reaction

d) Two molecules of ATP are produced by the pyruvate kinase reaction

e) Two molecules of NADH are produced by the pyruvate dehydrogenase reaction

13). All of the following help to explain some cases of Lactic Acidosis EXCEPT:

a) Poor oxygen uptake by blood in the lungs

b) Inhibition of phosphofructokinase-1

c) Not enough oxygen to satisfy the needs of oxidative phosphorylation

d) Congenital deficiency of liver lactate dehydrogenase

e) Inhibition of the electron transport chain.

14). All of the following are part of the Cori Cycle EXCEPT:

a) Lactate is the result of anaerobic glycolysis in a number of tissues

b) Lactate travels to the liver

c) Lactate is converted to glucose in the liver

d) ATP is produced by the conversion of lactate to glucose

e) Glucose travels from the liver to other tissues.

15). The ATP/AMP ratio has a major effect on the rate of ATP production by glycolysis.  ATP and AMP bind to allosteric sites on:

a) Hexokinase

b) Glucokinase

c) Phosphofructokinase-1

d) Phosphofructokinase-2

e) 3-phosphoglycerate kinase

16). Which of the following statements about adenylate kinase is FALSE:

a) Can convert ADP into ATP and AMP

b) Can convert AMP into ADP using phosphate transfer from ATP

c) Is also called myokinase

d) Can be classified as a nucleoside monophosphate kinase

e) Can be classified as a nucleoside diphosphokinase

17). When cells use energy, the greatest change is seen in the concentration of:

a) Creatine phosphate

b) ATP

c) ADP

d) AMP

e)Pi

18). In the liver, all of the following are part of the pathway whereby increased glucagon causes a decrease in the glycolytic pathway EXCEPT:

a) Increased binding of GTP to G-protein

b) Activation of the cAMP cascade

c)Increased phosphorylation of enzymes by protein kinase A

d)Activation of fructose-2,6-bisphosphatase and inhibition of phosphofructokinase-2

e) Increased binding of fructose-2,6-bisphosphate to phosphofructokinase-1

19). In the muscle, all of the following are part of the pathway whereby increased epinephrine causes an increase in the glycolytic pathway EXCEPT:

a) Increased binding of GTP to G-protein

b) Activation of the cAMP cascade

c) Increased phosphorylation of enzymes by protein kinase A

d) Activation of fructose-2,6-bisphosphatase and inhibition of phosphofructokinase-2

e) Increased binding of fructose-2,6-bisphosphate to phosphofructokinase-1

20). In the liver, high glucagon will inhibit glycolysis at more than one enzyme.  When entering the fasting state, the insulin to glucagon ratio drops and all of the following occur EXCEPT:

a) Protein kinase A will phosphorylate pyruvate kinase

b)The pyruvate kinase step will be activated

c) Protein kinase A will phosphorylate phosphofructokinase-2/fructose-2,6-bisphosphatase

d) The concentration of fructose-2,6-bisphosphate will decrease

e)The liver will not be able to synthesize pyruvate from phosphoenolpyruvate

21) Your patient has a chronic obstructive pulmonary disease so not enough oxygen is reaching her tissues.  You would expect all of the following EXCEPT

a) The electron transport chain would be inhibited

b) Glycolysis would be activated by a low ATP/ADP ratio

c) Concentrations of NADH and pyruvate would be lower than normal

d) Less than normal amounts of H⁺would be pumped out of the mitochondria

e) Less than normal amounts of ATP would be synthesized by ATP synthase

22) Your patient has been walking and begins to sprint.  All of the following changes would occur EXCEPT:

a) ATP hydrolysis by muscle would increase

b) ADP concentrations would increase and glycolysis would be activated

c) Pyruvate oxidation by the pyruvate dehydrogenase complex would increase

d) Acetyl CoA oxidation by the TCA cycle would decrease

e) Concentrations of NADH, pyruvate, and lactate in the cytosol would increase

23) All of the following are part of the explanation of dental caries by oral bacteria EXCEPT:

a)These bacteria use anaerobic glycolysis to produce much of their energy

b) Anaerobic glycolysis produces a lot of lactate

c) Lactate has a pKa of 10

d) Below a pH of 5.5, decalcification of tooth enamel and dentine occurs

e) Hydroxyapatite like crystals dissolve in acid solution.

24) Concerning the following reaction, all of the following answers are true EXCEPT?

2ADP = AMP + ATP

a) The enzyme is found in muscle tissue and is called myokinase

b) The enzyme is found in many cell types and is called adenylate kinase

c) The reaction is an example of substrate-level phosphorylation

d) The reaction can produce ATP for muscle contraction during severe muscle contraction

e) The enzyme can use ATP to convert AMP to ADP when the muscle is relaxed

25) All of the following are true EXCEPT? When one begins to exercise, the increased epinephrine will react with Β-receptors on muscle cells and

a) Activate the cAMP cascade

b) Inactivate Protein kinase A

c) Activate Phosphofructokinase-2 by phosphorylation

d) Increase the concentration of fructose-2,6-bisphosphate

e) Activate phosphofructokinase-1

26) All of the following are true EXCEPT? In the fasting state and in the liver:

a) Glucagon will activate the cAMP cascade

b) Protein kinase A will be activated

c) Phosphofructokinase-1 will be phosphorylated

d) Pyruvate kinase will be phosphorylated

e) Phosphoenolpyruvate will not be converted to pyruvate.

27) Your patient has a chronic obstructive pulmonary disease so not enough oxygen is reaching her tissues. You would expect all of the following EXCEPT?

a) A low blood pH due in part to high blood CO₂

b) A low blood pH due in part to high serum lactate

c) A partial inhibition of the electron transport chain due to lack of O₂

d) A partial inhibition of anaerobic glycolysis due to high ATP

e) A partial inhibition of the TCA cycle due to high NADH.

28) Your patient has been walking and begins to sprint. All of the following changes would occur in muscle cells EXCEPT:

a) The ATP concentrations would decrease and the ADP and AMP concentrations would increase

b) The rate of oxidation of NADH in the mitochondria by the electron transport chain would increase

c) The rate of phosphofructokinase-1 reaction would increase due to increased ATP

d) The rate of conversion of pyruvate to lactate would increase

e) The rate of conversion of pyruvate to acetyl CoA would increase.

Key to answers

1. c
2. c
3. e
4. b
5. d
6. b
7. a
8. c
9. c
10. b
11. b
12. e
13. b
14. d
15. e
16. e
17. d
18. e
19. d
20. b
21. c
22. c
23. c
24. c
25. b
26. c
27. d
28. c