Carbohydrate Metabolism: Interactive Learning Quizzes for Medical Students

Question 1

Which of the following is NOT a product of glycolysis?

Accepted Answer

Acetyl-CoA

Answer

Pyruvate

Answer

ATP

Answer

Lactate

Question 2

Gluconeogenesis is primarily regulated by:

Accepted Answer

Glucagon

Answer

Insulin

Answer

Glucose-6-phosphate

Answer

Fructose-2,6-bisphosphate

Question 3

Which enzyme is responsible for the breakdown of glycogen?

Accepted Answer

Glycogen phosphorylase

Answer

Glycogen synthetase

Answer

Hexokinase

Answer

Glucose-6-phosphatase

Question 4

The pentose phosphate pathway is essential for the production of:

Accepted Answer

NADPH

Answer

Glucose

Answer

Glycogen

Answer

Pyruvate

Question 5

Which of the following conditions is characterized by an inability to convert glycogen to glucose?

Accepted Answer

Glycogen storage disease

Answer

Diabetes

Answer

Hypoglycemia

Answer

Hyperglycemia

Question 6

Which hormone stimulates glycogen synthesis?

Accepted Answer

Insulin

Answer

Glucagon

Answer

Epinephrine

Answer

Cortisol

Question 7

Fructose-2,6-bisphosphate is a potent activator of:

Accepted Answer

Phosphofructokinase-1

Answer

Fructose-1,6-bisphosphatase

Answer

Pyruvate kinase

Answer

Glycogen synthase

Question 8

Which enzyme catalyzes the conversion of fructose 6-phosphate to fructose 1,6-bisphosphate, an irreversible step in glycolysis?

Accepted Answer

Phosphofructokinase-1

Answer

Aldolase

Answer

Glyceraldehyde 3-phosphate dehydrogenase

Answer

Pyruvate kinase

Question 9

What is the main purpose of gluconeogenesis in the body?

Accepted Answer

To synthesize glucose from non-carbohydrate sources

Answer

To break down glucose to produce energy

Answer

To convert glycogen to glucose

Answer

To generate fatty acids from glucose

Question 10

Which enzyme is primarily responsible for providing NADPH for the pentose phosphate pathway?

Accepted Answer

Glucose 6-phosphate dehydrogenase

Answer

Glyceraldehyde 3-phosphate dehydrogenase

Answer

Transketolase

Answer

Ribose 5-phosphate isomerase

Question 11

Which of the following is an inherited disorder that primarily affects carbohydrate metabolism?

Accepted Answer

Galactosemia

Answer

Phenylketonuria

Answer

Sickle cell anemia

Answer

Tay-Sachs disease

Question 12

Which molecule inhibits the enzyme fructose-1,6-bisphosphatase, thereby regulating gluconeogenesis?

Accepted Answer

Fructose 2,6-bisphosphate

Answer

Fructose 1-phosphate

Answer

Glucose-6-phosphate

Question 13

During glycolysis, which enzyme catalyzes the irreversible phosphorylation of glucose to glucose-6-phosphate?

Accepted Answer

Hexokinase

Answer

Glucokinase

Answer

Glycogen phosphorylase

Answer

Phosphoglucoisomerase

Question 14

In gluconeogenesis, the conversion of pyruvate to phosphoenolpyruvate (PEP) is a crucial step. Which of the following enzymes facilitates this conversion?

Accepted Answer

Phosphoenolpyruvate carboxykinase (PEPCK)

Answer

Pyruvate carboxylase

Answer

Lactate dehydrogenase

Answer

Glucose-6-phosphatase

Question 15

Which metabolic pathway generates ribose-5-phosphate, a precursor essential for nucleotide synthesis?

Accepted Answer

Pentose phosphate pathway

Answer

Glycolysis

Answer

Gluconeogenesis

Answer

Citric acid cycle

Question 16

During glycolysis, the conversion of 1,3-bisphosphoglycerate (BPG) to 3-phosphoglycerate results in the generation of:

Accepted Answer

ATP

Answer

NADH

Answer

FADH2

Answer

GTP

Question 17

The pentose phosphate pathway produces NADPH, which is primarily utilized for:

Accepted Answer

Glutathione synthesis

Answer

Fatty acid synthesis

Answer

Cholesterol synthesis

Answer

Amino acid synthesis

Question 18

Which of the following is a common disorder associated with defects in glycogen metabolism?

Accepted Answer

Glycogen storage disease

Answer

Diabetes mellitus

Answer

Mitochondrial myopathy

Answer

Cystic fibrosis

Question 19

Which enzyme catalyzes the conversion of fructose-6-phosphate to fructose-1,6-bisphosphate in glycolysis?

Accepted Answer

Phosphofructokinase

Answer

Hexokinase

Answer

Phosphoglycerate kinase

Answer

Pyruvate kinase

Question 20

What is the primary function of gluconeogenesis?

Accepted Answer

To synthesize glucose from non-carbohydrate sources like lactate and pyruvate

Answer

To synthesize glycogen from glucose

Answer

To produce ATP

Answer

To generate NADPH

Question 21

Which enzyme catalyzes the first committed step in the pentose phosphate pathway, producing ribulose-5-phosphate?

Accepted Answer

Glucose-6-phosphate dehydrogenase

Answer

Ribulose-5-phosphate isomerase

Answer

Transketolase

Answer

Transaldolase

Question 22

Which intermediate in the TCA cycle is used as a substrate for GTP production?

Accepted Answer

Succinyl-CoA

Answer

Citrate

Answer

α-Ketoglutarate

Answer

Oxaloacetate

Question 23

What is the primary role of glycogen phosphorylase?

Accepted Answer

To degrade glycogen to release glucose units

Answer

To synthesize glycogen from glucose-1-phosphate

Answer

To convert glucose-6-phosphate to glucose-1-phosphate

Answer

To regulate the activity of glycogen synthase

Question 24

Which enzyme catalyzes the cleavage of fructose-1,6-bisphosphate into glyceraldehyde-3-phosphate and dihydroxyacetone phosphate?

Accepted Answer

Aldolase

Answer

Triose phosphate isomerase

Answer

Glyceraldehyde-3-phosphate dehydrogenase

Answer

Phosphoglycerate kinase

Question 25

What is the total number of ATP molecules produced per molecule of glucose completely oxidized through glycolysis, the TCA cycle, and oxidative phosphorylation?

Accepted Answer

38

Answer

2

Answer

32

Answer

36

Question 26

Which of the following is NOT a substrate for gluconeogenesis?

Accepted Answer

Acetyl-CoA

Answer

Alanine

Answer

Pyruvate

Answer

Glycerol

Question 27

Which substance serves as the primary energy source for glycolysis?

Accepted Answer

Glucose

Answer

Fructose

Answer

Galactose

Answer

Glycogen

Question 28

What is the end product of glycolysis?

Accepted Answer

Pyruvate

Answer

Acetyl-CoA

Answer

Lactate

Answer

Glycerol

Question 29

Which enzyme catalyzes the conversion of glucose-6-phosphate to fructose-6-phosphate, an essential step in glycolysis?

Accepted Answer

Glucose-6-phosphate isomerase

Answer

Phosphofructokinase-1

Answer

Aldolase

Answer

Hexokinase

Question 30

What is the primary purpose of the pentose phosphate pathway?

Accepted Answer

Generation of NADPH and ribose-5-phosphate

Answer

Production of glucose from non-carbohydrate sources

Answer

Conversion of pyruvate to acetyl-CoA

Answer

Synthesis of glycogen from glucose

Question 31

Identify the rate-limiting enzyme in the gluconeogenesis pathway.

Accepted Answer

Phosphoenolpyruvate carboxykinase

Answer

Fructose-1,6-bisphosphatase

Answer

Glyceraldehyde-3-phosphate dehydrogenase

Answer

Pyruvate kinase

Question 32

Which of the following is not a potential source of glucose for gluconeogenesis?

Accepted Answer

Fatty acids

Answer

Lactate

Answer

Glycerol

Answer

Amino acids

Question 33

What is the significance of the Cori cycle in carbohydrate metabolism?

Accepted Answer

Facilitates the transport of lactate from skeletal muscle to the liver for gluconeogenesis

Answer

Converts pyruvate to acetyl-CoA for energy production

Answer

Generates NADPH for antioxidant defense

Answer

Synthesizes glycogen from glucose-6-phosphate

Question 34

Which disorder is characterized by a deficiency of the enzyme glucose-6-phosphate dehydrogenase?

Accepted Answer

G6PD deficiency

Answer

Galactosemia

Answer

Tyrosinemia

Answer

Fructose intolerance

Question 35

What is the primary energy source for the brain?

Accepted Answer

Glucose

Answer

Lactate

Answer

Ketone bodies

Answer

Glycerol

Question 36

Explain the dual roles of the pentose phosphate pathway in cellular defense and nucleotide synthesis. Discuss the clinical consequences of its dysfunction.

Accepted Answer

Provides NADPH for antioxidant reactions and ribose for nucleotide synthesis.

Answer

Generates glucose for energy production.

Answer

Regulates glycogen storage.

Answer

Participates in protein synthesis.

Question 37

Under aerobic conditions, pyruvate is converted to which molecule to enter the citric acid cycle? Under anaerobic conditions, what is pyruvate reduced to?

Accepted Answer

Acetyl-CoA; Lactate

Answer

Carbon dioxide; Water

Answer

Glucose; Carbon dioxide

Question 38

Which hormone plays a crucial role in stimulating gluconeogenesis?

Accepted Answer

Glucagon

Answer

Epinephrine

Answer

Insulin

Answer

Cortisol

Question 39

Identify the primary storage form of glucose in humans and animals?

Accepted Answer

Glycogen

Answer

Starch

Answer

Glucose-6-phosphate

Question 40

Which enzyme is responsible for the breakdown of glycogen to glucose-1-phosphate?

Accepted Answer

Glycogen phosphorylase

Answer

Hexokinase

Answer

Glucose-6-phosphatase

Answer

Glycogen synthase

Question 41

What is the primary function of the pentose phosphate pathway?

Accepted Answer

Generation of NADPH and ribose-5-phosphate for nucleotide and nucleic acid synthesis

Answer

Synthesis of fatty acids

Answer

Production of ATP

Answer

Detoxification of xenobiotics

Question 42

Which genetic disorder results from a deficiency in glucose-6-phosphate dehydrogenase?

Accepted Answer

G6PD deficiency

Answer

Sickle cell anemia

Answer

Hemochromatosis

Answer

Cystic fibrosis

Question 43

Which substrate undergoes oxidation to produce NADH during glycolysis?

Accepted Answer

Glyceraldehyde-3-phosphate

Answer

Phosphoenolpyruvate

Answer

Glucose-6-phosphate

Answer

Fructose-1,6-bisphosphate

Question 44

What is the main function of the electron transport chain?

Accepted Answer

Generate a proton gradient across the inner mitochondrial membrane, driving ATP synthesis

Answer

Generate ATP directly

Answer

Reduce NADH and FADH2

Question 45

A patient presents with fatigue, muscle cramps, and elevated lactate levels. Genetic testing reveals a deficiency in the enzyme phosphofructokinase-1 (PFK-1). Which metabolic pathway is most directly impacted in this patient?

Accepted Answer

Glycolysis

Answer

Gluconeogenesis

Answer

Pentose Phosphate Pathway

Answer

Glycogenolysis

Question 46

Which molecule acts as a key allosteric activator of phosphofructokinase-1 (PFK-1), promoting glycolysis?

Accepted Answer

Fructose-2,6-bisphosphate

Answer

ATP

Answer

Citrate

Answer

Glucose-6-phosphate

Question 47

Gluconeogenesis is essential for maintaining blood glucose levels during prolonged fasting. Which statement accurately describes a key difference between gluconeogenesis and glycolysis?

Accepted Answer

Gluconeogenesis bypasses the irreversible steps of glycolysis using different enzymes.

Answer

Gluconeogenesis requires ATP, while glycolysis produces ATP.

Answer

Gluconeogenesis primarily occurs in the muscle tissue, while glycolysis takes place in the liver.

Answer

Gluconeogenesis utilizes fatty acids as its primary substrate, while glycolysis utilizes glucose.

Question 48

A patient with uncontrolled type 1 diabetes presents with ketoacidosis. This condition arises due to the excessive accumulation of ketone bodies. What is the primary precursor molecule for ketone body synthesis?

Accepted Answer

Acetyl-CoA

Answer

Glucose

Answer

Pyruvate

Answer

Glycogen

Question 49

Glycogen, the storage form of glucose, is primarily stored in which two organs?

Accepted Answer

Liver and skeletal muscle

Answer

Brain and heart

Answer

Pancreas and kidneys

Answer

Spleen and bone marrow

Question 50

Which hormone stimulates glycogen breakdown (glycogenolysis) and glucose release from the liver during periods of low blood sugar?

Accepted Answer

Glucagon

Answer

Epinephrine

Answer

Cortisol

Answer

Insulin

Question 51

The pentose phosphate pathway (PPP) is crucial for nucleotide biosynthesis. Which molecule is a key product of the PPP that serves as a precursor for nucleotide synthesis?

Accepted Answer

Ribose-5-phosphate

Answer

Glyceraldehyde-3-phosphate

Answer

Fructose-6-phosphate

Answer

Glucose-6-phosphate

Question 52

Individuals with glucose-6-phosphate dehydrogenase (G6PD) deficiency may experience hemolytic anemia. What is the primary reason for this condition?

Accepted Answer

Insufficient NADPH production, leading to increased oxidative stress in red blood cells

Answer

Reduced ATP production, leading to cell death

Answer

Excessive accumulation of glucose-6-phosphate, causing cell lysis

Answer

Defective heme synthesis, impairing oxygen transport

Question 53

During strenuous exercise, muscle cells rely on anaerobic glycolysis for ATP production. What is the primary fate of pyruvate generated through anaerobic glycolysis in muscle cells?

Accepted Answer

Conversion to lactate

Answer

Entry into the citric acid cycle

Answer

Conversion to alanine

Answer

Utilization in gluconeogenesis

Question 54

The Cori cycle describes the metabolic interplay between the liver and muscle tissue. What is the primary function of the Cori cycle?

Accepted Answer

To regenerate glucose from lactate produced during anaerobic metabolism in muscle

Answer

To provide amino acids for protein synthesis in both liver and muscle

Answer

To transport ketone bodies from the liver to the muscles for energy production

Answer

To facilitate the conversion of pyruvate to glucose in the liver