Question 1

Which of the following best describes the primary function of enzymes in cellular metabolism?

Accepted Answer

They lower the activation energy of biochemical reactions, thereby increasing the reaction rate.

Question 2

A microbiology student observes that an enzyme-catalyzed reaction slows dramatically when the pH is changed from 7.0 to 4.0. What is the most likely explanation for this observation?

Accepted Answer

The enzyme is denatured due to the acidic environment, altering its active site.

Question 3

Which of the following equations correctly represents substrate-level phosphorylation?

Accepted Answer

$$ADP + P_i + 	ext{energy from substrate} \rightarrow ATP + 	ext{product}$$

Question 4

During fermentation, which of the following is a typical end product, and how does the ATP yield compare to aerobic respiration?

Accepted Answer

Lactic acid; ATP yield is much lower than aerobic respiration.

Question 5

Which of the following best describes oxidative phosphorylation?

Accepted Answer

ATP is generated using energy released by electrons as they are transferred to oxygen in the electron transport chain.

Question 6

In prokaryotic cells, where does the electron transport chain occur?

Accepted Answer

In the plasma (cell) membrane

Question 7

Which of the following statements correctly compares the location of glycolysis in prokaryotic and eukaryotic cells?

Accepted Answer

Glycolysis occurs in the cytoplasm of both prokaryotic and eukaryotic cells.

Question 8

Which of the following best describes chemiosmosis in eukaryotic cells?

Accepted Answer

The movement of protons ($$H^+) $$across the inner mitochondrial membrane, generating ATP via ATP synthase.

Question 9

What happens to all the carbons in glucose during aerobic respiration?

Accepted Answer

They are released as $$CO_2$$ during the Krebs cycle and pyruvate oxidation.

Question 10

A cell is undergoing fermentation. What happens to the electrons from NADH generated during glycolysis?

Accepted Answer

They are transferred to pyruvate or its derivatives, regenerating NAD$$^+.$$

Question 11

Saccharomyces is grown in two cultures: Culture A with oxygen and Culture B without oxygen. Which statement best describes the ATP production and end products in each culture?

Accepted Answer

Culture A produces more ATP and $$CO_2$$ and water; Culture B produces less ATP and ethanol.

Question 12

Which of the following equations represents the net ATP yield from aerobic respiration of one molecule of glucose in eukaryotic cells?

Accepted Answer

$$C_6H_{12}O_6$ + 6O_2 \rightarrow 6CO_2 + 6H_2O + 36-38 ATP$$

Question 13

Which process is responsible for the majority of ATP generated during aerobic respiration?

Accepted Answer

Oxidative phosphorylation via the electron transport chain and chemiosmosis

Question 14

Which of the following is a key difference between substrate-level phosphorylation and oxidative phosphorylation?

Accepted Answer

Substrate-level phosphorylation transfers a phosphate group directly from a substrate to ADP, while oxidative phosphorylation uses a proton gradient to drive ATP synthesis.

Question 15

In a eukaryotic cell, which of the following correctly matches the process with its cellular location?

Accepted Answer

Krebs cycle: mitochondrial matrix

Question 16

Which of the following best explains why facultative anaerobes like Saccharomyces produce more ATP in the presence of oxygen?

Accepted Answer

Oxygen serves as the final electron acceptor in the electron transport chain, allowing for complete oxidation of glucose and maximal ATP production.

Question 17

During aerobic respiration, what is the fate of the electrons originally present in glucose?

Accepted Answer

They are transferred to oxygen, forming water.

Question 18

Which of the following best describes the role of ATP synthase in chemiosmosis?

Accepted Answer

It uses the energy from the proton gradient to synthesize ATP from ADP and $$P_i.$$

Question 19

Which of the following is a correct summary of the fate of glucose carbons and electrons in fermentation?

Accepted Answer

Carbons are converted to organic end products (like ethanol or lactic acid), and electrons are transferred to these end products.

Question 20

A patient with a mitochondrial disorder is unable to efficiently carry out oxidative phosphorylation. Which of the following would you expect to observe in their cells?

Accepted Answer

Decreased ATP production and increased reliance on glycolysis and fermentation.

Microbial Metabolism: Enzymes, Energy Pathways, and Cellular Respiration

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