Q: Which reaction is catalyzed by phosphoglucomutase in glycogen metabolism?

$$\text{Glucose-1-phosphate} \rightarrow \text{Glucose-6-phosphate}$$

Q: Which of the following reactions summarizes the net result of glycogen biosynthesis?

$$\text{Glucose-6-phosphate} + ATP \rightarrow \text{Glycogen} + H_2O + ADP + 2\text{Pi}$$

Question 1

Which enzyme is responsible for catalyzing the sequential phosphorolysis of glucose residues from the nonreducing ends of glycogen?

Accepted Answer

Glycogen phosphorylase

Question 2

During glycogen breakdown, what is the fate of the glucose-1-phosphate produced by glycogen phosphorylase?

Accepted Answer

It is converted to glucose-6-phosphate by phosphoglucomutase.

Question 3

Which of the following statements about the branching enzyme in glycogen synthesis is correct?

Accepted Answer

It forms $$\alpha(1 \rightarrow 6)$$ linkages by transferring a block of 4-7 glucose residues to a more interior position.

Question 4

What is the main advantage of the highly branched structure of glycogen?

Accepted Answer

It allows for rapid release and storage of glucose due to multiple nonreducing ends.

Question 5

Which cofactor is required by glycogen phosphorylase for its activity?

Accepted Answer

Pyridoxal-5'-phosphate (PLP)

Question 6

A patient has a deficiency in the debranching enzyme. Which of the following would most likely accumulate in their cells?

Accepted Answer

Limit dextrin

Question 7

Which reaction is catalyzed by phosphoglucomutase in glycogen metabolism?

Accepted Answer

$$	ext{Glucose-1-phosphate} ightarrow 	ext{Glucose-6-phosphate}$$

Question 8

Which enzyme is responsible for synthesizing $$\alpha(1 \rightarrow 4)$$ glycosidic linkages in glycogen?

Accepted Answer

Glycogen synthase

Question 9

In the process of glycogen biosynthesis, which molecule acts as the glucose donor for chain elongation?

Accepted Answer

UDP-glucose

Question 10

Which of the following best describes the role of the debranching enzyme during glycogen degradation?

Accepted Answer

It hydrolyzes $$\alpha(1 \rightarrow 6)$$ linkages and transfers a block of glucose residues to another chain.

Question 11

Which of the following reactions summarizes the net result of glycogen biosynthesis?

Accepted Answer

$$	ext{Glucose-6-phosphate} + ATP ightarrow 	ext{Glycogen} + H_2O + ADP + 2	ext{Pi}$$

Question 12

Why is the efficiency of storing glucose as glycogen considered high?

Accepted Answer

Because 97% of the energy from glucose is retained after accounting for ATP used in biosynthesis.

Question 13

Which of the following steps in glycogen metabolism is NOT reversible?

Accepted Answer

Conversion of glucose-1-phosphate to UDP-glucose

Question 14

A mutation in the gene encoding glycogen synthase would most directly affect which process?

Accepted Answer

Glycogen biosynthesis

Question 15

Which of the following is TRUE regarding the action of glycogen phosphorylase?

Accepted Answer

It releases glucose-1-phosphate from the nonreducing ends of glycogen.

Question 16

Which enzyme is responsible for converting UDP-glucose to glycogen during biosynthesis?

Accepted Answer

Glycogen synthase

Question 17

In a scenario where a person is fasting, which process is most critical for maintaining blood glucose levels?

Accepted Answer

Glycogenolysis

Question 18

Which of the following best explains why the branching enzyme transfers a block of glucose residues to a position at least four residues away from an existing branch point?

Accepted Answer

To prevent steric hindrance and ensure efficient enzyme access during synthesis and degradation.

Question 19

Which of the following is a direct product of the action of the debranching enzyme's $$\alpha(1 \rightarrow 6)$$ glucosidase activity?

Accepted Answer

Free glucose

Glycogen Metabolism: Structure, Degradation, and Biosynthesis

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