Hexokinase; $$\text{Glucose} + \text{ATP} \rightarrow \text{Glucose-6-phosphate} + \text{ADP}$$

Phosphoglycerate kinase; $$\text{3-Phosphoglycerate}$$

Question 1

Which of the following best describes the two distinct phases of glycolysis?

Accepted Answer

An energy-investment phase and an energy-generation phase

Question 2

During glycolysis, how many net ATP molecules are produced per molecule of glucose?

Accepted Answer

$$2$$

Question 3

Which enzyme catalyzes the first irreversible step of glycolysis, and what is the reaction it catalyzes?

Accepted Answer

Hexokinase; $$	ext{Glucose} + 	ext{ATP} ightarrow 	ext{Glucose-6-phosphate} + 	ext{ADP}$$

Question 4

Which glycolytic enzyme is a major control point and is regulated allosterically?

Accepted Answer

Phosphofructokinase (PFK)

Question 5

A patient presents with a deficiency in the enzyme aldolase. Which step of glycolysis would be directly affected?

Accepted Answer

Cleavage of fructose-1,6-bisphosphate into two triose phosphates

Question 6

Which reaction in glycolysis is responsible for the first substrate-level phosphorylation, and what is the product?

Accepted Answer

Phosphoglycerate kinase; $$	ext{3-Phosphoglycerate}$$

Question 7

Why is the overall reaction catalyzed by pyruvate kinase exergonic, even though ATP synthesis is endergonic?

Accepted Answer

Due to the spontaneous tautomerization of enolpyruvate to the more stable keto form (pyruvate)

Question 8

Under anaerobic conditions, what is the primary reason that pyruvate is converted to lactate or ethanol?

Accepted Answer

To reoxidize NADH to NAD$$^+$$, allowing glycolysis to continue

Question 9

Which three glycolytic enzymes catalyze reactions that must be bypassed in gluconeogenesis?

Accepted Answer

Hexokinase, phosphofructokinase, pyruvate kinase

Question 10

Which organ is the most active in gluconeogenesis, especially during fasting or prolonged exercise?

Accepted Answer

Liver

Question 11

What is the main metabolic requirement of the pentose phosphate pathway (PPP)?

Accepted Answer

To provide NADPH for reductive biosynthesis and ribose-5-phosphate for nucleotide synthesis

Question 12

Which enzyme is responsible for cleaving $$\alpha(1 \rightarrow 4)$$ glycosidic bonds in glycogen via phosphorolysis?

Accepted Answer

Glycogen phosphorylase

Question 13

In glycogen catabolism, what is the role of the bifunctional debranching enzyme?

Accepted Answer

It transfers three glucose residues to another nonreducing end and removes the remaining glucose at the branch point

Question 14

Which enzyme converts $$\alpha-D-$$glucose-1-phosphate to $$\alpha-D-$$glucose-6-phosphate, allowing entry into glycolysis?

Accepted Answer

Phosphoglucomutase

Question 15

Which process mobilizes dietary polysaccharides to monosaccharides, and which process mobilizes intracellular carbohydrate stores?

Accepted Answer

Hydrolysis for dietary polysaccharides; phosphorolysis for intracellular stores

Question 16

Which enzyme is required to remove the limit dextrin during the digestion of amylopectin or glycogen?

Accepted Answer

$$\alpha(1$$ \rightarrow 6)$-glucosidase (debranching enzyme)

Question 17

What is the activated form of glucose used for glycogen synthesis?

Accepted Answer

UDP-glucose

Question 18

Which enzyme catalyzes the synthesis of $$\alpha(1 \rightarrow 4)-$$linked glycogen from UDP-glucose?

Accepted Answer

Glycogen synthase

Question 19

How are futile cycles between glycolysis and gluconeogenesis prevented in cells?

Accepted Answer

By reciprocal regulation of key enzymes

Question 20

Which hormone stimulates glycogen breakdown in muscle and liver by activating the cAMP cascade?

Accepted Answer

Glucagon

Glycolysis, Gluconeogenesis, and Glycogen Metabolism

Study Guide - Practice Questions