Carbohydrate Metabolism

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1
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1. Which of the following enzymes, involved in the breakdown of carbohydrates in the
digestive tract of humans, has/have small intestine origin?
1) sucrase
2) glucoamylase
3) lactase
4) α- amylase
a) 1+2+3
b) 1+3
c) 2+4
d) 4

ANSWER: a) 1+2+3

2
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2. The absorption of glucose through the mucous membrane of enterocytes in the human
is performed via one of the listed types of transport proteins. Which is that?
a) glucose transporter type 2 (GLUT2)
b) glucose transporter type 5 (GLUT5)
c) Na-dependent glucose transporter (SGLT1)
d) glucose transporter type 1 (GLUT1)

ANSWER: c) Na-dependent glucose transporter (SGLT1)

3
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3. Which of the following symptoms are typical for mono- and disaccharidases
malabsorption (intolerance) and lactose intolerance?
1) diarrhea
2) distension the intestine
3) painful colics
4) meteorism
a) 1+2+3
b) 1+3
c) 2+4
d) 1+2+3+4

ANSWER: d) 1+2+3+4

4
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4. Which of the following co-enzymes does not participate in the pyruvate
dehydrogenase complex:
a) pyridoxalphosphate
b) thiamine pyrophosphate
c) coenzyme-A
d) lipoic acid

ANSWER: a) pyridoxalphosphate

5
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5. Which of the following enzymes involved in the glycolysis is the major regulatory
enzyme of this pathway:
a) Phosphofructokinase-2 (PFK-2)
b) Aldolase
c) Phosphoglycerate kinase
d) Phosphofructokinase-1 (PFK-1)

ANSWER: d) Phosphofructokinase-1 (PFK-1)

6
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6. Which of the following metabolites is not an allosteric modulator of the main
regulatory enzyme of glycolysis:
a) ATP
b) Glucose-6-phosphate
c) AMP
d) Fructose-2,6-bisphosphate

ANSWER: b) Glucose-6-phosphate

7
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7. In which of the following cells the anaerobic glycolysis is performed:
1) white muscle fibers (during active contraction)
2) cells of the renal medulla
3) erythrocytes
4) cells of the eye lens
a) 1+2+3
b) 1+3
c) 2+4
d) 1+2+3+4

ANSWER: d) 1+2+3+4

8
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8. Which of the following substances is a direct product of the action of the enzyme
glycogen phosphorylase (glycogenolysis):
a) Glucose-6-phosphate
b) Glucose
c) Glucose-1-phosphate
d) None of the mentioned above

ANSWER: c) Glucose-1-phosphate

9
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9. Which of the following enzyme catalyzes the conversion of glucose to glucose-6-
phosphate in muscle cells:
a) Glucose-6-phosphatase
b) Glucokinase
c) Phosphoglucomutase
d) Hexokinase

ANSWER: d) Hexokinase

10
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10. Which of the following enzymes uses NAD.H as coenzyme in reduction process in
anaerobic glycolysis:
a) Pyruvate kinase
b) Enolase
c) Lactate dehydrogenase
d) Glyceraldehyde-3-phosphate dehydrogenase

ANSWER: c) Lactate dehydrogenase

11
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11. Which of the following statements about the malate-aspartate shuttle is not true:
a) The shuttle is bidirectional
b) Cytoplasmic and mitochondrial malate dehydrogenases participate in the
shuttle
c) The oxidation in the respiratory chain of the two pairs of reducing
equivalents transferred by the shuttle mechanism, leads to the synthesis
of 4 ATP molecules
d) The pair of substrates involved in the shuttle are oxaloacetate and malate

ANSWER: c) The oxidation in the respiratory chain of the two pairs of reducing
equivalents transferred by the shuttle mechanism, leads to the synthesis
of 4 ATP molecules

12
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12. Which of the following enzymes are involved in the first, non-oxidizing phase of the
glycolytic pathway?:
1) phosphohexosoisomerase
2) phosphofructokinase 1
3) hexokinase
4) enolase
a) 1+2+3
b) 1+3
c) 2+4
d) All of the mentioned above

ANSWER: a) 1+2+3

13
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13. Which of the following enzymes catalyzes the synthesis of fructose-2,6-
bisphosphate, appearing as the strongest activator of the regulatory enzyme of
glycolysis:
a) Hexokinase
b) Phosphofructokinase 2
c) Phosphoglycerate kinase
d) Phosphofructokinase 1

ANSWER: b) Phosphofructokinase 2

14
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14. Select the correct answer of the question: In how many ATP molecules the energy
released from the anaerobic glycolysis is accumulated?
a) Two
b) Eight
c) Thirty six
d) Four

ANSWER: a) Two

15
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15. Which of the following hormones has an effect on the liver cells, resulting in the
formation of active dephosphorylated kinase form of the enzyme
phosphofructokinase 2:
a) Glucagon
b) Adrenaline
c) Insulin
d) None of the mentioned above

ANSWER: c) Insulin

16
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16. Which of the following metabolic pathways of glucose supplies reducing equivalents
for the synthesis of fatty acids, cholesterol and other reductive processes.
a) Glycolysis
b) Gluconeogenesis
c) Pentose phosphate pathway
d) Oxidative decarboxylation of pyruvate

ANSWER: c) Pentose phosphate pathway

17
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17. Which of the listed deficiencies (of enzymes and/or vitamins) lead to lactic acidosis?
1) thiamine
2) erythrocyte enzymes of glycolysis
3) enzymes of pyruvate dehydrogenase complex
4) muscle enzymes of glycolysis
a) 1+2+3
b) 1+3
c) 2+4
d) All of the mentioned above

ANSWER: b) 1+3

18
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18. Which of the following statements about the pentose phosphate pathway of glucose
is wrong:
a) It is performed actively in skeletal muscle
b) Supplies NADPH for fatty acid, cholesterol biosynthesis etc..
c) The acyl-CoA derivatives inhibit the regulatory enzyme
d) In the first (oxidation) step of the process 2 molecules NADPH are obtained

ANSWER: a) It is performed actively in skeletal muscle

19
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19. Which of the following enzymes of the glycolytic pathway catalyzes the step, which
is a oxidative phosphorylation at the substrate level, ie carries out the synthesis of
ATP when a metabolite is oxidized:
a) Phosphofructokinase 1
b) Hexokinase
c) Pyruvate kinase
d) Phosphoglucomutase

ANSWER: c) Pyruvate kinase

20
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20. Which of the following enzymes of the glycolytic pathway is regulated by a covalent
modification:
a) Pyruvate kinase
b) Phosphofructokinase 1
c) Aldolase
d) Phosphoglucomutase

ANSWER: a) Pyruvate kinase

21
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21. The risk of hemolytic anemia is associated with the deficiency of one of the
following enzymes of the pentose-phosphate pathway. Which is that enzyme?
a) Transketolase
b) Phosphogluconolaktonase
c) Glucose-6-phosphate dehydrogenase
d) Transaldolase

ANSWER: c) Glucose-6-phosphate dehydrogenase

22
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22. Which of the following co-enzymes serve as such of the enzyme of the pentose
phosphate pathway, transketolase, and by measuring the enzymatic activity of
transketolase is diagnosed a possible deficiency of this vitamin in the body:
a) pyridoxal phosphate
b) thiamine pyrophosphate
c) NADP
d) FAD

ANSWER: b) thiamine pyrophosphate

23
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23. In which of the following types of cells the transport of glucose is insulinindependent:
1) adipocytes
2) brain
3) skeletal muscle cells
4) erythrocytes
a) 1+2+3
b) 1+3
c) 2+4
d) None of the above mentioned

ANSWER: c) 2+4

24
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24. Which of the following statements about the pentose phosphate pathway in mature
erythrocytes is true:
a) Provides ribose-5-phosphate for the synthesis of nucleotides
b) Provides NADPH for fatty acid synthesis
c) Provides NADPH for maintaining the level of reduced glutathione,
necessary for the disposal of Н2О2
d) Provides NADPH of cholesterol synthesis

ANSWER: c) Provides NADPH for maintaining the level of reduced glutathione,
necessary for the disposal of Н2О2

25
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25. Which of the following statements about the transport of glucose from the blood into
the cells of skeletal muscle is wrong:
a) the transport is carried out by a glucose transporter (facilitated diffusion)
b) insulin stimulates glucose transport through the export of glucose carriers on
the cell membrane, i.e. by increasing the number of transporters on the cell
membrane
c) the glucose enters the cells of the skeletal muscle along the concentration
gradient
d) Insulin induces the biosynthesis of an enzyme which catalyzes
phosphorylation of the free glucose to glucose-6-phosphate

ANSWER: d) Insulin induces the biosynthesis of an enzyme which catalyzes
phosphorylation of the free glucose to glucose-6-phosphate

26
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26. Which of the following metabolites serve as substrates for the synthesis of glucose in
the gluconeogenesis:
1) pyruvate
2) oxaloacetate
3) glycerol
4) acetyl-CoA
a) 1+2+3
b) 1+3
c) 2+4
d) All of the above mentioned

ANSWER: a) 1+2+3

27
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27. Which of the following enzymes involved in gluconeogenesis, is the most important
regulatory enzyme in the process, subjected to allosteric regulation of variety of
modulators:
a) pyruvate carboxylase
b) glucose-6-phosphatase
c) fructose-1,6-bisphosphatase
d) phosphoenolpyruvate-carboxykinase (PEPKK

ANSWER: c) fructose-1,6-bisphosphatase

28
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28. Which of the following enzymes of gluconeogenesis does not use energy of ATP, but
of GTP.
a) pyruvate carboxylase
b) phosphoglycerate kinase
c) glucose-6-phosphatase
d) phosphoenolpyruvate-carboxykinase (PEPKK)

ANSWER: d) phosphoenolpyruvate-carboxykinase (PEPKK)

29
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29. Which of the following hormones stimulates the gluconeogenesis by inducing
biosynthesis of phosphoenolpyruvate-carboxykinase (PEPKK) and other specific
enzymes of gluconeogenesis:
a) Cortisol
b) Insulin
c) Aldosterone
d) Adenocorticotropic hormone (ACTH)

ANSWER: a) Cortisol

30
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30. Which of the following metabolites of the citrate cycle can be directly converted to
phosphoenolpyruvate, and thus be incorporated into the gluconeogenesis:
a) Citrate
b) Oxaloacetate
c) α- -Ketoglutarate
d) Fumarate

ANSWER: b) Oxaloacetate

31
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31. The failure of which of these enzymes involved in the catabolism of fructose results
into the hereditary disease "congenital fructose intolerance":
a) Fructokinase
b) Aldolase B
c) Ttriosokinase
d) none of the above mentioned

ANSWER: b) Aldolase B

32
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32. Which of the following enzymes involved in the catabolism of galactose catalyze the
metabolic step of the conversion of galactose to galactose-1-phosphate
a) Galactose-1-phosphate uridyltransferase
b) UDF- galactose-4-epimerase
c) Galactokinase
d) Phosphoglucomutase

ANSWER: c) Galactokinase

33
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33. Which of the following enzymes functioning in gluconeogenesis, is allosterically
activated by Acetyl-CoA:
a) Glucose-6-phosphatase
b) Fructose-1,6-bisphosphatase
c) Phosphoenolpyruvate-carboxykinase (PEPKK)
d) Pyruvate carboxylase

ANSWER: d) Pyruvate carboxylase

34
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34. Which of the activated forms of glucose is used as a direct substrate for the synthesis
of glycogen:
a) Glucose-6-phosphate
b) Glucose-1-phosphate
c) UDP-glucose
d) None of the above mentioned

ANSWER: c) UDP-glucose

35
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35. Which of these metabolites is the allosteric activator of phosphorylated glycogen
synthase b:
a) АTP
b) АМP
c) glucose-6-phosphate
d) fructose-2,6-bisphosphate

ANSWER: c) glucose-6-phosphate

36
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36. Glycerol is a non-carbohydrate precursor for the synthesis of glucose in
gluconeogenesis. To which of the listed metabolites of gluconeogenesis turns the
glycerol to:
a) Pyruvate
b) Dihydroxyacetone phosphate
c) Phosphonenolpyruvate
d) Fructose-6-phosphate

ANSWER: b) Dihydroxyacetone phosphate

37
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37. Which of the following statements about the metabolism of liver glycogen is true:
a) During its degradation lactate is released in the blood
b) Glucagon stimulates its synthesis
c) It is broken down during the periods of fasting
d) adrenaline stimulates its synthesis

ANSWER: c) It is broken down during the periods of fasting

38
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38. In which of the following organs the gluconeogenesis is performed:
1) liver
2) small intestine
3) renal cortex
4) skeletal muscles
a) 1+2+3
b) 1+3
c) 2+4
d) All of the above mentioned

ANSWER: b) 1+3

39
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39. Which of the following metabolic steps of gluconeogenesis is common for glycolysis
and gluconeogenesis:
a) fructose-6-phosphate → Glucose-6-phosphate
b) pyruvate →oxaloacetate
c) fructose-1,6-bisphosphate → fructose-6-phosphate
d) oxaloacetate → phosphonenolpyruvate

ANSWER: a) fructose-6-phosphate → Glucose-6-phosphate

40
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40. Alcohol (ethanol) inhibits the gluconeogenesis. Which of the following statements
about the inhibitory effect of ethanol is wrong:
a) oxidation of the ethanol leads to an increased level of NAD.H in hepatocytes
b) the high levels of NAD.H direct the lactate dehydrogenase reaction to the
conversion of pyruvate to lactate, which lowers the concentration of pyruvate
as a precursor of gluconeogenesis.
c) ethanol itself serves as inhibitor of the enzymes involved in
gluconeogenesis.
d) ethanol decreases the concentration of other substrates for gluconeogenesis, in
pyruvate (e.g., oxaloacetate)

ANSWER: c) ethanol itself serves as inhibitor of the enzymes involved in
gluconeogenesis.

41
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41. Which of the following enzymes involved in glycogen metabolism, catalyzes the
phosphorolytic breakdown of α-1,4-glycosidic bond:
a) glycogen synthase
b) glycogen phosphorylase
c) phosphoglucomutase
d) amylo-1,4 → 1,6-transglycosylase

ANSWER: b) glycogen phosphorylase

42
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42. Which of the following statements about the metabolism of liver glycogen is wrong:
a) it is synthesized after carbohydrate-rich food intake
b) insulin stimulates its synthesis
c) it is broken down in conditions with high blood glucose levels
d) by degradation it provides blood glucose

ANSWER: c) it is broken down in conditions with high blood glucose levels

43
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43. Which of the following statements about the influence of insulin on blood glucose
level is wrong:
a) Insulin reduces the level of blood glucose by accelerating its transport from the
blood into insulin-dependent tissues
b) Insulin stimulates the synthesis of liver and muscle glycogen
c) Insulin does not stimulate glucose transport in adipose tissue
d) Insulin stimulates glycolysis in the liver

ANSWER: c) Insulin does not stimulate glucose transport in adipose tissue

44
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44. Which of the following enzymes is not present in the muscles that could explain the
fact that skeletal muscles do not release blood glucose after the breakdown of
glycogen:
a) kinase of phosphorylase
b) phosphoglucomutase
c) glucose-6-phosphatase
d) glycogen phosphorylase

ANSWER: c) glucose-6-phosphatase

45
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45. The following enzymes and hormones are involved in the cascade of events leading
to degradation of muscle glycogen under stress. Indicate which of them does not
participate:
a) Adrenaline
b) Adenylyl cyclase
c) Protein kinase A
d) Glucagon

ANSWER: d) Glucagon

46
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46. Which of the following statements about the effects of cortisol on the blood glucose
level is correct:
a) cortisol increases blood glucose level by stimulating the glycogenolysis
b) cortisol increases blood glucose level by stimulating gluconeogenesis
c) cortisol decreases blood glucose level by increasing the uptake of glucose into
cells
d) cortisol decreases blood glucose level by stimulating the glycolysis

ANSWER: b) cortisol increases blood glucose level by stimulating gluconeogenesis

47
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47. Which of the following statements about the mechanism by which insulin affects the
activity of glycogen synthase (regulatory enzyme of glycogenogenesis) is wrong:
a) insulin decreases the level of cAMP, which leads to dropout of the activation
of Protein kinase A, catalyzing the formation of the active phosphorylated
form of the protein, called "inhibitor-1"
b) When the inhibitory protein-1 is inactive (dephosphorylated) it does not inhibit
the activity of proteinphosphstase - 1
c) the active protein phosphatase-1 catalyzes the dephosphorylation of glycogen
synthase (glycogen synthase a)
d) insulin signaling leads to creating of the phosphorylated form of glycogen
synthase (glycogen synthase b)

ANSWER: d) insulin signaling leads to creating of the phosphorylated form of glycogen
synthase (glycogen synthase b)

48
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48. The breakdown of liver glycogen is stimulated by glucagon via one of the listed
below secondary cell messengers. Which is that messenger?
a) calcium ions
b) cAMP
c) diacylglycerol
d) inositol-triphosphate

ANSWER: b) cAMP

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49. Which of the following symptoms is not typical for patients with diabetes:
a) glucosuria
b) ketoacidosis
c) hypoglycemia
d) polyuria

ANSWER: c) hypoglycemia

50
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50. Which of the following hormones is a major regulator of blood glucose level after
meals:
a) glucagon
b) insulin
c) adrenaline
d) cortisol

ANSWER: b) insulin