Section іv Structure and metabolism of carbohydrates

1. The irreversible reactions of glycolysis include that catalyzed by:

1. 6-phosphofructo-1-kinase.

2. fructose-bisphosphate aldolase.se.

3. phosphoglucose isomerase.

4. glyceraldehyde-3-phosphate dehydrogenase.

5. phosphoglycerate kinase.

2. In yeast cells occurs a process which is similar to glycolysis - alcohol fermentation. In course of this process through several stages from pyruvate is produced:

1. Ethanol

2. Lactate

3. Acetaldehyde

4. Glyceraldehyde

5. Pyruvate

3. Glucokinase:

1. Has a high Km for glucose and hence is important in the phosphorylation of glucose primarily after ingestion of a carbohydrate rich meal

2. None of these

3. Is widely distributed and occurs in most mammalian tissues

4. Is widely distributed in Prokaryotes

4. The reaction catalysed by phosphofructokinase:

1. Is the rate-limiting reaction of the glycolytic pathway

2. Is activated by high concentrations of ATP and citrate

3. Uses fructose-1-phosphate as substrate

4. Is inhibited by ADP

5. Is inhibited by fructose 2, 6-bisphosphate

5. Compared to the resting state, vigorously contracting muscle shows:

1. An increased conversion of pyruvate to lactate

2. Decreased oxidation of pyruvate of CO₂ and water

3. A increased NADH/NAD+ ratio

4. Decreased concentration of AMP

6. Pasteur effect is:

1. Inhibition of anaerobic glycolysis

2. Oxygen is not involved

3. Inhibition of enzyme phosphofructokinase

4. Activation of lactate synthesis

5. All of these

7. Which one of the following would be expected in pyruvate kinase deficiency?

1. Hemolytic anemia

2. Increased levels of lactate in the R.B.C

3. Decreased ratio of ADP to ATP in R.B.C

4. Increased phosphorylation of Glucose to Glucose-6-phosphate

5. Increased levels of pyruvate

8. Which one of the following statements concerning glucose metabolism is correct?

1. Glucose enters most cells by a mechanism in which Na+ and glucose are co-transported

2. The conversion of Glucose to lactate occurs only in the R.B.C

3. Pyruvate kinase catalyses an irreversible reaction

4. An elevated level of insulin leads to a decreased level of fructose 2, 6-bisphosphatein hepatocyte

9. Anaerobic oxidation of glucose to lactate is regulated by appropriate enzymes. What enzyme is the major regulator of this process?

1. Phosphofructokinase

2. Lactate dehydrogenase

3. Glucose-6-phosphate isomerase

4. Aldolase

5. Enolase

10. 6-Posphofructokinase activity can be decreased by all of the following EXCEPT:

1. AMP

2. ATP at high concentration

3. citrate

4. low pH

5. decreased concentration of fructose 2, 6-bisphosphate

11. During glycolysis, Fructose 1,6-biphosphate is decomposed by the enzyme:

1. Aldolase

2. Enolase

3. Fructokinase

4. Diphosphofructophosphatase

5. Hexokinase

12. The oxidation of lactic acid to pyruvic acid requires the following vitamin derivative as the hydrogen carrier.

1. NAD⁺

2. Lithium pyrophosphate

3. Coenyzme A

4. FMN

5. FAD

13. Erythrocytes require energy of ATP for their vital functions. What process provides these cells with the necessary amount of ATP?

1. Anaerobic glycolysis

2. Aerobic oxidation of glucose

3. Pentose phosphate pathway

4. Oxidation of fatty acids

5. Citric acid cycle

14. Alcoholic fermentation occurs in yeast and several bacterial species. In this process product of pyruvate decarboxylation is:

A. Acetaldehyde

B. Lactate

C. Ethanol

D. Phosphoenolpyruvate

E. glucose

15. Which of the following enzymes is not involved in glycolysis?

1. Glucose oxidase

2. Enolase

3. Aldolose

4. Hexokinase

5. Glucokinase

16. The combination of subunits in lactate dehydrogenase molecule makes it possible to create the next number of isoenzymes:

1. Five

2. Three

3. Four

4. Six

5. Eight

17. In aerobic glycolysis glucose is transformed to:

A. Pyruvic acid

B. Ethylic alcohol

C. Lactic acid

D. Citric acid

E. Acetyl-CoA.

18. All of the following statements apply to the digestive enzyme α–amylase EXEPT:

1. It catalyses the hydrolysis of α1→4 glycosidic linkages exept those of glucose unit that serve as branch points

2. Glycogen and hydrated starch are normal substrates

3. The form of α–amylase in human pancreas is the most important isoenzyme

4. Glucose is the major product of α–amylase action on starch

5. Cellulose, a plant carbohydrate, is not hydrolysed by α–amylase in man