Question 1

Which of the following best describes the role of ATP in cellular energy metabolism?

Accepted Answer

ATP is an intermediate that conserves, transfers, and releases energy within the cell.

Question 2

During glycolysis, which enzyme catalyzes the phosphorylation of glucose to glucose-6-phosphate, and why is this step important?

Accepted Answer

Hexokinase; it traps glucose inside the cell by phosphorylating it, making it unable to exit.

Question 3

What is the net ATP yield from one molecule of glucose during glycolysis?

Accepted Answer

2 ATP

Question 4

Which of the following equations correctly represents the hydrolysis of ATP at pH 7?

Accepted Answer

$$\mathrm{ATP} + \mathrm{H}_2\mathrm{O} \rightarrow \mathrm{ADP} + \mathrm{P}_i + \mathrm{H}^+$$

Question 5

Which compound has the highest standard free energy of hydrolysis according to Table 9.1?

Accepted Answer

Phosphoenolpyruvate (PEP)

Question 6

In the context of glycolysis, what is substrate-level phosphorylation?

Accepted Answer

The direct synthesis of ATP from ADP and a phosphorylated substrate by an enzyme.

Question 7

Which of the following best explains why glycolysis can occur in both aerobic and anaerobic conditions?

Accepted Answer

Glycolysis does not require oxygen as an electron acceptor.

Question 8

Which of the following is a correct summary equation for alcoholic fermentation in yeast?

Accepted Answer

$$\mathrm{glucose} + 2\mathrm{ADP} + 2\mathrm{P}_i + 2\mathrm{H}^+ \rightarrow 2\mathrm{ethanol} + 2\mathrm{CO}_2 + 2\mathrm{ATP}$$

Question 9

During strenuous exercise, muscle cells switch to lactic acid fermentation. What is the main purpose of this switch?

Accepted Answer

To regenerate NAD$$^+ so $$glycolysis can continue in the absence of oxygen.

Question 10

Which enzyme is responsible for the second irreversible step in glycolysis, and what is its regulatory significance?

Accepted Answer

Phosphofructokinase; it is an allosteric enzyme that regulates the pace of glycolysis.

Question 11

Which of the following best describes the fate of pyruvate in obligate anaerobes?

Accepted Answer

Pyruvate is reduced to lactate or ethanol, depending on the organism.

Question 12

Which of the following statements about redox reactions in cellular metabolism is correct?

Accepted Answer

Reduction occurs when a molecule gains electrons.

Question 13

Which of the following is a correct summary equation for glycolysis?

Accepted Answer

$$\mathrm{glucose} + 2\mathrm{NAD}^+ + 2\mathrm{ADP} + 2\mathrm{P}_i \rightarrow 2\mathrm{pyruvate} + 2\mathrm{NADH} + 2\mathrm{H}^+ + 2\mathrm{ATP}$$

Question 14

Which compound is produced by phosphorolytic cleavage of glycogen or starch?

Accepted Answer

Glucose-1-phosphate

Question 15

Which of the following best explains why phosphoenolpyruvate (PEP) can drive ATP synthesis via substrate-level phosphorylation?

Accepted Answer

PEP has a higher free energy of hydrolysis than ATP, allowing transfer of its phosphate to ADP.

Question 16

Which of the following is a real-world example of fermentation?

Accepted Answer

Bread rising due to yeast converting glucose to ethanol and CO$$_2$$

Question 17

Which molecule acts as the primary electron carrier during glycolysis?

Accepted Answer

NAD$$^+$$

Question 18

Which regulatory enzyme is influenced by fructose-2,6-bisphosphate in glycolysis?

Accepted Answer

Phosphofructokinase-1 (PFK-1)

Question 19

Which of the following best describes gluconeogenesis?

Accepted Answer

The synthesis of glucose from non-carbohydrate precursors.

Ch.9: Chemotrophic Energy Metabolism-Glycolysis and Fermentation

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