Question 1

Which of the following best describes the role of acetyl-Coenzyme A in cellular metabolism?

Accepted Answer

It is the two-carbon molecule that enters the citric acid cycle for further oxidation.

Question 2

During glycolysis, what is the net gain of ATP molecules per molecule of glucose?

Accepted Answer

$$2$$

Question 3

Which enzyme catalyzes the conversion of glucose to glucose 6-phosphate, and what is the significance of this step?

Accepted Answer

Hexokinase; it traps glucose inside the cell by phosphorylation.

Question 4

Which of the following statements about the electron transport chain is correct?

Accepted Answer

It creates a proton gradient across the inner mitochondrial membrane, which drives ATP synthesis.

Question 5

What is the primary function of insulin in glucose metabolism?

Accepted Answer

To decrease blood glucose by signaling cells to take in glucose.

Question 6

Which pathway is responsible for synthesizing glucose from noncarbohydrate sources such as amino acids and glycerol?

Accepted Answer

Gluconeogenesis

Question 7

In the absence of oxygen, what is the fate of pyruvate in human muscle cells?

Accepted Answer

It is reduced to lactate to regenerate NAD$$^+$$ for glycolysis.

Question 8

Which of the following best explains why glucose 6-phosphate cannot leave the cell once formed?

Accepted Answer

The phosphate group is charged, preventing it from crossing the cell membrane unaided.

Question 9

How many molecules of carbon dioxide are produced from the complete oxidation of one molecule of glucose, and during which stages are they released?

Accepted Answer

$$6$$; during pyruvate oxidation and the citric acid cycle

Question 10

Which hormone is released when blood glucose levels drop, and what is its primary effect?

Accepted Answer

Glucagon; stimulates glycogen breakdown and glucose release from the liver

Question 11

Which of the following is a correct description of the fate of NADH produced during glycolysis under aerobic conditions?

Accepted Answer

It donates electrons to the electron transport chain, leading to ATP production.

Question 12

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

Accepted Answer

Glycogenolysis

Question 13

What is the main purpose of the pentose phosphate pathway?

Accepted Answer

To convert glucose to five-carbon sugar phosphates and generate NADPH

Question 14

Which of the following best describes the regulation of phosphofructokinase in glycolysis?

Accepted Answer

It is activated by ADP and AMP, and inhibited by ATP and citrate.

Question 15

Which of the following is a direct product of the citric acid cycle for each acetyl-CoA molecule entering the cycle?

Accepted Answer

$$3$$ NADH, $$1$$ FADH$$_2$$, $$1$$ GTP, $$2 CO$_2$$

Question 16

A patient is experiencing hypoglycemia after fasting for 24 hours. Which metabolic pathway is most responsible for maintaining their blood glucose levels?

Accepted Answer

Glycogenolysis

Question 17

Which of the following best explains why fats are not a direct source of glucose during starvation?

Accepted Answer

Fatty acids cannot be converted to glucose because there is no pathway to convert acetyl-CoA to pyruvate or oxaloacetate.

Question 18

Which of the following is a correct description of the Cori cycle?

Accepted Answer

It is the process by which lactate produced in muscles is transported to the liver and converted back to glucose.

Question 19

Which of the following best describes the fate of galactose after it is absorbed from the digestive tract?

Accepted Answer

It is converted to glucose 6-phosphate and enters glycolysis.

Carbohydrate Metabolism: Pathways, Regulation, and Energy Yield

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