Question 1

Which of the following best describes the main function of glycolysis in cellular metabolism?

Accepted Answer

To convert glucose into two molecules of pyruvic acid, producing a net gain of 2 ATP and 2 NADH.

Question 2

What determines whether pyruvic acid will enter the citric acid cycle or be converted to lactic acid after glycolysis?

Accepted Answer

The presence or absence of oxygen.

Question 3

Which of the following equations correctly represents the overall reaction for aerobic respiration of glucose?

Accepted Answer

$$\mathrm{C_6H_{12}O_6$ + 6O_2 \rightarrow 6CO_2 + 6H_2O + ATP}$$

Question 4

During anaerobic metabolism in muscle cells, what is the fate of NADH produced in glycolysis?

Accepted Answer

It donates electrons to pyruvic acid, regenerating NAD and forming lactic acid.

Question 5

Why is lactic acid fermentation not favored by the body for long-term ATP production?

Accepted Answer

It produces much less ATP and leads to acid buildup, which can impair cell function.

Question 6

Which enzyme is responsible for converting lactic acid back to pyruvic acid in the liver?

Accepted Answer

Lactic acid dehydrogenase

Question 7

What is the main purpose of the transition step between glycolysis and the citric acid cycle?

Accepted Answer

To convert pyruvic acid into acetyl CoA, releasing CO2.

Question 8

Where does the citric acid (Krebs) cycle occur within the cell?

Accepted Answer

In the mitochondrial matrix

Question 9

Which two coenzymes are reduced during the citric acid cycle and later donate electrons to the electron transport chain?

Accepted Answer

NAD and FAD

Question 10

What is the final electron acceptor in the electron transport chain?

Accepted Answer

Oxygen ($$\mathrm{O_2$})$$

Question 11

If a cell produces 2 NADH molecules, how many ATP are theoretically generated from these in the electron transport chain?

Accepted Answer

$$2 	imes 3 = 6$$ ATP

Question 12

Why can only the liver release glucose into the bloodstream after glycogenolysis?

Accepted Answer

Only the liver contains glucose 6-phosphatase, which removes the phosphate group from glucose-6-phosphate.

Question 13

Which process describes the formation of glucose from non-carbohydrate sources such as amino acids or lactic acid?

Accepted Answer

Gluconeogenesis

Question 14

What is the main function of the Cori cycle?

Accepted Answer

To convert lactic acid produced in muscles back to glucose in the liver.

Question 15

Which of the following best explains why glucose cannot be stored as free glucose in cells?

Accepted Answer

Glucose attracts water by osmosis, causing cells to swell and potentially lyse.

Question 16

What is the process called when triglycerides are broken down into fatty acids and glycerol for energy?

Accepted Answer

Lipolysis

Question 17

A 16-carbon fatty acid can theoretically yield how many ATP after complete oxidation?

Accepted Answer

$$108$$ ATP

Question 18

What is the main reason ketone bodies are produced in the liver?

Accepted Answer

When the rate of lipolysis exceeds the rate of fatty acid utilization, leading to excess acetyl CoA.

Question 19

Which of the following is NOT a product of the citric acid cycle?

Accepted Answer

Glucose

Question 20

Which of the following statements about the interconversion of energy sources is correct?

Accepted Answer

Amino acids can be converted into glucose via gluconeogenesis.

Respiration and Metabolism: Biochemical Pathways of Energy Production

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