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Biochemistry > Glycogen Metabolism and Gluconeogenesis > Flashcards

Glycogen Metabolism and Gluconeogenesis Flashcards

1
Q

Which of the enzyme is responsible for the hydrolysis of α (1-6) glycosidic bond present at a
branching point of glycogen molecules?
a) β-Glucosidase
b) α- Glucosidase
c) Glycosidase
d) Phosphorylase

A

b) α- Glucosidase

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2
Q

During starvation,
pyruvate kinase is inhibited by ——————–

A

phosphorylation

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3
Q

Phosphorylation ——- Glycogen Phosphorylase

A

Activates

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4
Q

Formation of one molecule of glucose from pyruvate requires____________
A. 4 ATP, 2 GTP and 2 NADH
B. 3 ATP, 2 GTP and 2 NADH
C. 4 ATP, 1 GTP and 2 NADH
D. 2 ATP, 2 GTP and 2 NADH

A

A. 4 ATP, 2 GTP and 2 NADH

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5
Q

Under anaerobic conditions the glycolysis of one mole of glucose yields ______moles of ATP.
(A) One
(B) Two
(C) Eight
(D) Thirty

A

(B) Two

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6
Q

Synthesis of an activated form of glucose, UDP-glucose
from glucose 1-phosphate and UTP (uridine triphosphate) in a reaction catalyzed by ——————

A

UDP-glucose pyrophosphorylase

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7
Q

lactate and some glucogenic amino acids
are first converted to ——–,
other glucogenic amino acids enter the gluconeogenic pathway as —————

A

pyruvate
oxaloacetate

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8
Q

Which of the following statements about gluconeogenesis is correct?

A. Pyruvate is first converted to phosphoenolpyruvate byphosphoenolpyruvate carboxykinase
B. Fructose 1, 6-biphosphatase converts fructose 1, 6-bisphosphate into fructose 1-phosphate
C. Glucose 6-phosphatase hydrolyzes glucose 6-phosphate to release glucose into the blood
D. Glucose 6-phosphatase hydrolyzes glucose 6-phosphate and is found in liver and muscle

A

C. Glucose 6-phosphatase hydrolyzes glucose 6-phosphate to release glucose into the blood

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9
Q

———- forms α-1,6-linkages that make glycogen a branched polymer

A

The branching enzyme

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10
Q

Cori’s cycle transfers
(A) Glucose from muscles to liver
(B) Lactate from muscles to liver
(C) Lactate from liver to muscles
(D) Pyruvate from liver to muscles

A

(B) Lactate from muscles to liver

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11
Q

Structure of glycogen

A
  • A very large branched polymer of glucose residues
  • Glycogen is present in the cytosol of animal cells in the form of granules
  • The two major sites of glycogen storage are the liver and skeletal muscle.
  • The core of the glycogen particle is a protein (glycogenin, G).
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12
Q

Control of pyruvate kinase activity:

A
  • by phosphorylation and dephosphorylation
  • by allosteric effectors
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13
Q

Branching is important because:

A

it increases the solubility of glycogen and increases the velocity of glycogen synthesis and breakdown (creating a large number of non-reducing ends).

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14
Q

Gluconeogenesis is the synthesis of glucose from nonsaccharide compounds:

A
  • lactate
  • glycerol
  • some amino acids (called glucogenic amino acids).
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15
Q

All the following enzymes are involved in glycogen synthesis, Except
a) Hexokinase
b) Phosphoglucomutase
c) Glucose-1-P uridylyltransferase
d) Glycogen synthetase

A

d) Glycogen synthetase

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16
Q

Phosphorylation ——- Glycogen Synthase

A

Inhibits

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17
Q

Which of the following organs does not have glycogen storage?
a) Liver
b) Muscle
c) Intestine
d) Erythrocytes

A

d) Erythrocytes

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18
Q

Explain what happens when blood glucose level is low

A
  • Hypoglycaemia
  • happens during fasting state
  • the pancreas b-cells releases the hormone Glucagon to stimulate Gluconeogenesis (synthesis of new glucose) and Glycogennolysis (breakdown of glycogen) in the liver
  • then release the glucose to the blood
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19
Q

Which of the following is false about glycogen molecules?
a) Glycogen is a polysaccharide
b) Glycogen is a polymer of beta-D-Glucose
c) Glycogen consists of α(1-4) and α (1-6) glycosidic linkage
d) Glycogen have are a helical structure with branching.

A

b) Glycogen is a polymer of beta-D-Glucose

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20
Q

Epinephrine stimulates glycogenolysis in
(A) Liver
(B) Muscle
(C) Liver and muscle
(D) Kidney

A

(C) Liver and muscle

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21
Q

A carbohydrate which can not be digested in human gut is
(A) Cellulose
(B) Starch
(C) Glycogen
(D) Maltose

A

(A) Cellulose

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22
Q

Two types of α-glucosidic bonds

A

α-1,6-glycosidic linkage at the branching point and α-1,4-glycosidic linkages

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23
Q

Which of the following statement is false regarding glycogenesis?
a) Glycogen synthase is activated in the phosphorylated state.
b) Glycogen synthase enzyme is inhibited by glucagon and epinephrine action.
c) Protein phosphatase removes the phosphate group and activates the enzyme
d) Insulin promotes glycogen synthesis in liver and skeletal muscles

A

a) Glycogen synthase is activated in the phosphorylated state.

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24
Q

The branching enzyme is the ————————-

A

amylo-(α-1,4α-1,6)-transglucosylase

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25
Q

Glycogen breakdown in cells requires the cooperation of two enzymes

A

– glycogen phosphorylase
– debranching enzyme.

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26
Q

In adipose tissue prostaglandins decrease
(A) Lipogenesis
(B) Lipolysis
(C) Gluconeogenesis
(D) Glycogenolysis

A

(A) Lipogenesis

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27
Q

Oxaloacetate is reduced to malate by ____________
A. Pyruvate carboxylase
B. Malate dehydrogenase
C. Pyruvate kinase
D. Phosphofructokinase-1

A

B. Malate dehydrogenase

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28
Q

Glycogen de-branching enzyme exhibits two catalytic activities, it is a bifunctional enzyme:

A

The transferase activity shifts a block of three glucosyl residues from one outer branch to the other, and
α-1,6-glucosidase activity hydrolysis the α-1,6-glycosidic bond resulting in the release of a free glucose molecule.

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29
Q

Which enzyme catalyzes the conversion of pyruvate to oxaloacetate?
A. Pyruvate carboxylase
B. Pyruvate dehydrogenase
C. Pyruvate kinase
D. Phosphofructokinase-1

A

A. Pyruvate carboxylase

30
Q

The Cori cycle

A

Gluconeogenesis in the liver transforms part of the lactate formed by active skeletal muscle to glucose

31
Q

An amphibolic pathway among the following is
(A) HMP shunt
(B) Glycolysis
(C) Citirc acid cycle
(D) Gluconeogenesis

A

(C) Citirc acid cycle

32
Q

Which of the following enzyme is responsible for glycogen breakdown?
a) Glycogen phosphorylase
b) Glycogen phosphatase
c) Glycogen hydrolase
d) Glycogen phospho beta-glucosidase

A

a) Glycogen phosphorylase

33
Q

Which of the following is not an enzyme involved in glycolysis?
(A) Enolase
(B) Aldolose
(C) Hexokinase
(D) Glucose oxidase

A

(D) Glucose oxidase

34
Q

During starvation, ketone bodies are used as a fuel by
(A) Erythrocytes
(B) Brain
(C) Liver
(D) All of these

A

(B) Brain

35
Q

Which of the following enzyme is responsible for the addition of UDP-Glucose to the existing
chain?
a) Glycogen synthase
b) Glycogen polymerase
c) Glycogen synthetase
d) Glycogen lyase

A

a) Glycogen synthase

36
Q

What is the main source of glucose carbons for gluconeogenesis?
A. Guanine
B. Alanine
C. Cysteine
D. Threonine

A

B. Alanine

37
Q

Phosphorylase can split —————–,
its action ends with the production of limit dextrin

A

α-1,4-links

38
Q

A polysacchharide which is often called animal starch is
(A) Glycogen
(B) Starch
(C) Inulin
(D) Dextrin

A

(D) Dextrin

39
Q

Which of the following organisms cannot convert acetyl-coA derived from fatty acids into glucose?
A. Animals
B. Plants
C. Bacteria
D. Virus

A

A. Animals

40
Q

Briefly explain the steps of Gluconeogenesis

A

1-Carboxylation of pyruvate to oxaloacetate by the enzyme pyruvate carboxylase, then Oxaloacetate is transported into the cytosol in the form of malate, which is then reoxidized to oxaloacetate

2- 2 Conversion of oxaloacetate to phosphoenolpyruvate (PEP), Oxaloacetate is simultaneously decarboxylated and phosphorylated by
phosphoenolpyruvate carboxykinase in the cytosol

3- Dephosphorylation of fructose 1,6-bisphosphate, The hydrolysis of fructose 1,6-bisphosphate to fructose 6-phosphate is catalyzed by fructose 1,6-bisphosphatase.

4- Glucose 6-phosphatase is present only in the liver cells and to a lesser extent in the kidney, only these tissues can release free glucose into the blood by dephosphorylation of glucose 6-phosphate to glucose by glucose 6-phosphatase that takes place within the lumen of smooth endoplasmic reticulum

41
Q

Insulin stimulates
(A) Hepatic glycogenolysis
(B) Hepatic glycogenesis
(C) Lipolysis
(D) Gluconeogenesis

A

(B) Hepatic glycogenesis

42
Q

Glycogen phosphorylase is responsible for the breakdown of glycogen
to……………………………………..
a) Glucose
b) Glucose-1-phosphate
c) Glucose-6-phosphate
d) Maltose

A

b) Glucose-1-phosphate

43
Q

The major site of daily glucose consumption (75%) is the —– via ——– pathways.

A

brain
aerobic

44
Q

The body obtains glucose from amino acids and lactate via. ————————–

A

gluconeogenesis

45
Q

Which of the following metabolite allosterically activate glycogen phosphorylase?
a) ATP
b) AMP
b) Glucose-6-P
d) Glucose-1-P

A

b) AMP

46
Q

The carbohydrate reserved in human body is
(A) Starch
(B) Glucose
(C) Glycogen
(D) Inulin

A

(C) Glycogen

47
Q

———— involves the formation of glucose from non-carbohydrate sources

A

Gluconeogenesis

48
Q

Liver glycogen contributes to the maintenance of glucose but not muscle glycogen.
Which of the following enzyme is absent in muscle?
a) Glycogen phosphorylase
b) Hexokinase
c) Glucose-6-phosphatase
d) Debranching enzyme

A

c) Glucose-6-phosphatase

49
Q

——— principal storage form of glucose mainly found in liver (10% of liver weight) and muscle, minor quantities in kidney and intestine.

A

Glycogen

50
Q

Explain what happens when blood glucose level is high

A
  • Hyperglycaemia
  • happens during Feeding state
  • the pancreas a-cells releases the hormone Insulin to stimulate Glycogenesis (synthesis of Glycogen) the liver or muscle
51
Q

Which of the following statements is false about gluconeogenesis?
A. From the hydrolysis of tri-acyl-glycerol, fatty acids can be used as a carbon source
B. From red blood cells, lactate can be used as a carbon source
C. From the hydrolysis of tri-acyl-glycerol, glycerol is converted to glucose in gluconeogenesis
D. From muscle vigorous muscle activity, lactate can be used as a carbon source

A

A. From the hydrolysis of tri-acyl-glycerol, fatty acids can be used as a carbon source

52
Q

Muscle glycogen is not generally available to other tissues, because muscle lacks the enzyme ———————– that converts it to glucose.

A

glucose-6-phosphatase

53
Q

Which of the following protein is required for de novo synthesis of glycogen?
a) Glycoprotein
b) Glycogenin
c) Proteoglycan
d) Glucogenin

A

b) Glycogenin

54
Q

phosphorylations are catalysed by the action of ———————-, dephosphorylations by the action of ————————————–

A
  • protein kinases
  • phosphoprotein phosphatases
55
Q

Which of the following is not the direct/ indirect activator of glycogen phosphorylase in muscle?
a) AMP
b) Ca++
c) Epinephrine
d) Insulin

A

d) Insulin

56
Q

Phosphoglucomutase converts glucose 1-phosphate into
———— the intermediate of glycolysis.

A

glucose 6-phosphate

57
Q

Glycogen is converted to glucose-1- phosphate by
(A) UDPG transferase
(B) Branching enzyme
(C) Phosphorylase kinase
(D) Phosphatase kinase

A

(C) Phosphorylase kinase

58
Q

Conversion of glucose to glucose-6- phosphate in human liver is by
(A) Hexokinase only
(B) Glucokinase only
(C) Hexokinase and glucokinase
(D) Glucose-6-phosphate dehydrogenase

A

(C) Hexokinase and glucokinase

59
Q

Glycerol enters the gluconeogenesis as ——————————

A

dihydroxyacetone phosphate

60
Q

Gluconeogenesis is decreased by
(A) Glucagon
(B) Epinephrine
(C) Glucocorticoids
(D) Insulin

A

(D) Insulin

61
Q

Uridine diphosphate glucose (UDPG) is
(A) Required for metabolism of galactose
(B) Required for synthesis of glucuronic acid
(C) A substrate for glycogen synthetase
(D) All of the above

A

(D) All of the above

62
Q

————– catalyses formation of an α-1,4-glycosidic bonds by the transfer of glucosyl from UDP-glucose to an existing chain

A

Glycogen synthase – the key regulatory enzyme in glycogenesis

63
Q

Oxidation of which substance in the body yields the most calories
(A) Glucose
(B) Glycogen
(C) Protein
(D) Lipids

A

(D) Lipids

64
Q

Growth hormone causes hyperglycemia.It is a result of
(A) Decreased peripheral utilization of glucose
(B) Decreased hepatic production via gluconeogenesis
(C) Increased glycolysis in muscle
(D) Decrersed lipolysis

A

(A) Decreased peripheral utilization of glucose

65
Q

Gluconeogenesis occurs in the —— (approximately 90 %)
and in the ——– (about 10 %),
only those two tissues can provide blood glucose by gluconeogenesis.

A

liver
kidney

66
Q

The following is an enzyme required for glycolysis:
(A) Pyruvate kinase
(B) Pyruvate carboxylase
(C) Glucose-6-phosphatase
(D) Glycerokinase

A

(A) Pyruvate kinase

67
Q

Gluconeogenesis is increase by
(A) Glucagon and Epinephrine
(B) inhibin
(C) Albumin
(D) Insulin

A

(A) Glucagon and Epinephrine

68
Q

Gluconeogenesis involves the conversion of ……
A. Glucose to pyruvate
B. Pyruvate to glucose
C. Phosphoenolpyruvate to glucose
D. Pyruvate to fructose

A

B. Pyruvate to glucose

69
Q

Gluconeogenesis is decreased by
(A) Glucagon
(B) Epinephrine
(C) Glucocorticoids
(D) Insulin

A

(D) Insulin

70
Q

———— refers to glycogen formation from carbohydrates.

A

glycogenesis

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