Biology

Cellular Respiration and Enzymes

1,721 Questions

Explore key concepts of cellular respiration, including glycolysis, the Krebs cycle, and the electron transport chain. These questions also cover ATP production, anaerobic respiration, and essential metabolic pathways. This topic forms a core part of the biology syllabus for many competitive examinations.

Glycolysis and metabolic pathwaysKrebs cycle processesElectron transport chainATP production countAnaerobic respiration products

Cellular Respiration and Enzymes Questions

Multiple choice

What is the difference between glycogenolysis and gluconeogenesis?

  1. Glycogenolysis breaks down glycogen, while gluconeogenesis synthesizes glucose from non-carbohydrate precursors.

  2. Glycogenolysis occurs in the liver, while gluconeogenesis occurs in the muscle.

  3. Glycogenolysis is stimulated by glucagon, while gluconeogenesis is stimulated by insulin.

  4. Glycogenolysis produces glucose-6-phosphate, while gluconeogenesis produces glucose.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Glycogenolysis breaks down glycogen into glucose, while gluconeogenesis synthesizes glucose from non-carbohydrate precursors, such as amino acids and lactate.

Multiple choice

What is the role of glycogenolysis in the Cori cycle?

  1. It converts lactate to glucose in the liver.

  2. It converts glucose to lactate in the muscle.

  3. It transports glucose from the liver to the muscle.

  4. It transports lactate from the muscle to the liver.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Glycogenolysis is involved in the Cori cycle, which is a process that converts lactate produced in the muscle during exercise back to glucose in the liver.

Multiple choice

What is the first step of glycolysis?

  1. Phosphorylation of glucose

  2. Isomerization of glucose-6-phosphate

  3. Cleavage of fructose-1,6-bisphosphate

  4. Oxidation of glyceraldehyde-3-phosphate
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The first step of glycolysis is the phosphorylation of glucose by hexokinase, which converts glucose into glucose-6-phosphate. This step requires one molecule of ATP.

Multiple choice

What is the net gain of ATP molecules during glycolysis?

  1. 2

  2. 4

  3. 6

  4. 8
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

During glycolysis, two molecules of ATP are consumed and four molecules of ATP are produced, resulting in a net gain of two ATP molecules.

Multiple choice

Which enzyme catalyzes the cleavage of fructose-1,6-bisphosphate into two three-carbon molecules?

  1. Phosphofructokinase-1

  2. Aldolase

  3. Triose phosphate isomerase

  4. Glyceraldehyde-3-phosphate dehydrogenase
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Aldolase catalyzes the cleavage of fructose-1,6-bisphosphate into two three-carbon molecules: glyceraldehyde-3-phosphate and dihydroxyacetone phosphate.

Multiple choice

What is the role of NAD+ in glycolysis?

  1. It is reduced to NADH.

  2. It is oxidized to NAD+.

  3. It is a cofactor for enzymes.

  4. It is a substrate for enzymes.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

NAD+ is reduced to NADH during glycolysis by glyceraldehyde-3-phosphate dehydrogenase. This reaction generates one molecule of NADH for each molecule of glyceraldehyde-3-phosphate that is oxidized.

Multiple choice

What is the final product of glycolysis?

  1. Pyruvate

  2. Acetyl-CoA

  3. Citrate

  4. Oxaloacetate
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The final product of glycolysis is pyruvate, which is a three-carbon molecule. Pyruvate is then converted into acetyl-CoA, which enters the citric acid cycle.

Multiple choice

How many molecules of ATP are produced during the conversion of one molecule of glucose to two molecules of pyruvate?

  1. 2

  2. 4

  3. 6

  4. 8
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

During the conversion of one molecule of glucose to two molecules of pyruvate, two molecules of ATP are produced during glycolysis and two molecules of ATP are produced during the conversion of pyruvate to acetyl-CoA. Therefore, the total ATP yield is 4 molecules of ATP.

Multiple choice

Which of the following is NOT a substrate for glycolysis?

  1. Glucose

  2. Fructose-1,6-bisphosphate

  3. Glyceraldehyde-3-phosphate

  4. Acetyl-CoA
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Acetyl-CoA is not a substrate for glycolysis. It is a product of glycolysis and enters the citric acid cycle.

Multiple choice

What is the name of the enzyme that catalyzes the isomerization of glucose-6-phosphate to fructose-6-phosphate?

  1. Hexokinase

  2. Phosphoglucomutase

  3. Phosphofructokinase-1

  4. Aldolase
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Phosphoglucomutase catalyzes the isomerization of glucose-6-phosphate to fructose-6-phosphate. This reaction is necessary for the continuation of glycolysis.

Multiple choice

Which of the following is NOT a product of glycolysis?

  1. Pyruvate

  2. Acetyl-CoA

  3. NADH

  4. ATP
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Acetyl-CoA is not a product of glycolysis. It is a product of the citric acid cycle, which occurs after glycolysis.

Multiple choice

What is the name of the enzyme that catalyzes the oxidation of glyceraldehyde-3-phosphate to 1,3-bisphosphoglycerate?

  1. Glyceraldehyde-3-phosphate dehydrogenase

  2. Phosphoglycerate kinase

  3. Phosphoglyceromutase

  4. Enolase
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Glyceraldehyde-3-phosphate dehydrogenase catalyzes the oxidation of glyceraldehyde-3-phosphate to 1,3-bisphosphoglycerate. This reaction is also known as the Embden-Meyerhof-Parnas pathway.

Multiple choice

Which of the following is NOT a step in glycolysis?

  1. Phosphorylation of glucose

  2. Isomerization of glucose-6-phosphate

  3. Cleavage of fructose-1,6-bisphosphate

  4. Decarboxylation of pyruvate
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Decarboxylation of pyruvate is not a step in glycolysis. It is a step in the citric acid cycle, which occurs after glycolysis.

Multiple choice

What is the name of the enzyme that catalyzes the conversion of 1,3-bisphosphoglycerate to 3-phosphoglycerate?

  1. Phosphoglycerate kinase

  2. Phosphoglyceromutase

  3. Enolase

  4. Pyruvate kinase
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Phosphoglycerate kinase catalyzes the conversion of 1,3-bisphosphoglycerate to 3-phosphoglycerate. This reaction generates one molecule of ATP for each molecule of 1,3-bisphosphoglycerate that is converted.

Multiple choice

Which of the following is NOT a fate of pyruvate after glycolysis?

  1. Conversion to acetyl-CoA

  2. Conversion to lactate

  3. Conversion to ethanol

  4. Conversion to oxaloacetate
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Conversion to oxaloacetate is not a fate of pyruvate after glycolysis. Oxaloacetate is a product of the citric acid cycle, which occurs after glycolysis.