9.4 Microbial Physiology Module 9: Metabolism

Which of the following reactions is involved in the conversion of pyruvate to acetyl coenzyme A?

• oxidative phosphorylation

• oxidative deamination

• oxidative decarboxylation

• oxidative transamination

Answer explanation

Answer: c. oxidative decarboxylation. Pyruvate undergoes oxidative decarboxylation, producing acetyl-CoA, CO₂, and NADH

Reference:

Brock et al., 2021

Which of the following gases is a by-product of the reaction between pyruvate and coenzyme A?

• CO

• CO₂

• O₂

• none of these

Answer explanation

Answer: b. CO₂. Carbon dioxide is a by-product of the oxidative decarboxylation of pyruvate

References:

Brock et al., 2021

Struck & White, 2019

Which of the following carbohydrates cannot enter the glycolytic pathway?

• Fructose

• Galactose

• Glycogen

• None of these

Answer explanation

Answer: c. glycogen. Glycogen must first be broken down into glucose or glucose-6-phosphate

Reference:

Blanco, A., & Blanco, G. (2017). Carbohydrate metabolism. In Elsevier eBooks (pp. 283–323). https://doi.org/10.1016/b978-0-12-803550-4.00014-8

Struck & White, 2019

Which of the following compounds is required to convert glyceraldehyde 3-phosphate to 1,3-bisphosphoglycerate?

• ADP

• ATP

• NADH

• NAD+

Answer explanation

Answer: d. NAD⁺. NAD² is reduced to NADH in this oxidation step

References:

Blanco, A., & Blanco, G. (2017). Carbohydrate metabolism. In Elsevier eBooks (pp. 283–323). https://doi.org/10.1016/b978-0-12-803550-4.00014-8

Brock et al., 2021

How many molecules of FADH2 are obtained for each acetyl CoA molecule that enters the common catabolic pathway?

• 1

• 2

• 3

• 4

Answer explanation

Answer: a. 1. One FADH₂ is generated for each acetyl-CoA oxidized in the citric acid cycle

Reference:

(Struck & White, 2019).

How many molecules of ATP are produced during the conversion of two molecules of 1,3-bisphosphoglycerate to yield two molecules of pyruvate?

• 2

• 4

• 6

• 12

Answer explanation

Answer: b. 4. Two ATP molecules are generated per 1,3-bisphosphoglycerate via substrate-level phosphorylation

References:

Struck & White, 2019

https://www.khanacademy.org/science/biology/cellular-respiration-and-fermentation/glycolysis/a/glycolysis

Which of the following acts as the oxidizing agent in the conversion of pyruvate to acetyl coenzyme A?

• ATP

• NAD+

• NADH

• Pyruvate

Answer explanation

Answer: b. NAD⁺. NAD⁺ accepts electrons, becoming NADH

References:

Struck & White, 2019

https://bio.libretexts.org/Bookshelves/Introductory_and_General_Biology/General_Biology_(Boundless)/07%3A_Cellular_Respiration/7.08%3A_Oxidation_of_Pyruvate_and_the_Citric_Acid_Cycle_-__Breakdown_of_Pyruvate#:~:text=The%20conversion%20of%20pyruvate%20to,CoA%20to%20produce%20Acetyl%20CoA.

Which of the following gases is a by-product of the reaction between pyruvate and coenzyme A?

• CO

• CO₂

• O₂

• none of these

Answer explanation

Answer: b. CO₂. CO₂ is a by-product of this reaction

Reference:

Brock et al., 2021

Which of the following statements is true of anaerobic reactions?

• They are all redox reactions.

• They are all oxidation reactions.

• They occur in the presence of oxygen.

• They occur in the absence of oxygen.

Answer explanation

Answer: d. They occur in the absence of oxygen. Anaerobic reactions proceed without oxygen, producing less ATP than aerobic pathways

References:

Struck & White, 2019

What is the effect of excess ATP on glycolysis?

• It enhances the rate of glycolysis.

• It moderately reduces the rate of glycolysis.

• It shuts down glycolysis.

• It has no effect on glycolysis.

Answer explanation

Answer: c. It shuts down glycolysis. ATP inhibits phosphofructokinase, slowing glycolysis when energy is abundant

Reference:

Brock et al., 2021