Question 1

Which of the following statements best describes the difference between prokaryotic and eukaryotic cells?

Accepted Answer

Eukaryotic cells have their DNA enclosed within a nucleus, whereas prokaryotic cells have their DNA in a nucleoid region without a surrounding membrane.

Question 2

A scientist isolates a microorganism with the following characteristics: it is unicellular, lacks a nucleus, has a cell wall containing peptidoglycan, and divides by binary fission. To which group does this organism most likely belong?

Accepted Answer

Bacteria

Question 3

Which of the following best explains why penicillin is selectively toxic to bacteria but not to human cells?

Accepted Answer

Penicillin inhibits the synthesis of peptidoglycan, a component unique to bacterial cell walls.

Question 4

Which of the following is a correct scientific name, following the rules of binomial nomenclature?

Accepted Answer

Escherichia coli

Question 5

A patient develops a persistent infection on a catheter. Laboratory analysis reveals the presence of a biofilm. Which of the following best explains why this infection is difficult to treat?

Accepted Answer

Biofilms protect bacteria from antibiotics and the immune system by forming a matrix of extracellular polymeric substances (EPS).

Question 6

Which of the following best describes the role of NAD+ in cellular metabolism?

Accepted Answer

NAD+ acts as an electron carrier, accepting electrons during oxidation reactions and becoming reduced to NADH.

Question 7

During glycolysis, glucose ($C_6H_{12}O_6$) is converted to two molecules of pyruvate. Which of the following best summarizes the net energy yield from glycolysis per molecule of glucose?

Accepted Answer

2 ATP (net), 2 NADH, and 2 pyruvate

Question 8

Which of the following statements about the Gram stain is correct?

Accepted Answer

Gram-positive bacteria retain the crystal violet stain because of their thick peptidoglycan layer.

Question 9

Which of the following best describes oxidative phosphorylation?

Accepted Answer

ATP is generated using energy released by the movement of protons across a membrane via ATP synthase.

Question 10

A bacterium is found to be pleomorphic. What does this mean?

Accepted Answer

It can exist in multiple shapes rather than a single, consistent shape.

Question 11

Which of the following is a function of the bacterial glycocalyx?

Accepted Answer

It protects the cell from desiccation and can help bacteria adhere to surfaces.

Question 12

Which of the following best explains why fermentation is important for cells under anaerobic conditions?

Accepted Answer

Fermentation regenerates NAD+ from NADH, allowing glycolysis to continue in the absence of oxygen.

Question 13

Which of the following is a correct pairing of a metabolic process and its primary electron acceptor?

Accepted Answer

Aerobic respiration – $O_2$

Question 14

A bacterial cell is placed in a hypotonic solution. What is the most likely outcome if the cell wall is damaged?

Accepted Answer

The cell will undergo osmotic lysis as water enters the cell.

Question 15

Which of the following best describes the function of ATP in cellular metabolism?

Accepted Answer

ATP couples energy-releasing (exergonic) reactions to energy-requiring (endergonic) reactions.

Question 16

Which of the following is a product of the citric acid cycle (per turn)?

Accepted Answer

1 ATP (or GTP), 3 NADH, 1 FADH$_2$

Question 17

Which of the following is a major difference between Gram-positive and Gram-negative bacterial cell walls?

Accepted Answer

Gram-negative cell walls contain an outer membrane and a thin peptidoglycan layer, while Gram-positive cell walls have a thick peptidoglycan layer and no outer membrane.

Question 18

Which of the following best describes the role of the electron transport chain in cellular respiration?

Accepted Answer

It transfers electrons from NADH and FADH$_2$ to oxygen, creating a proton gradient used to generate ATP.

Question 19

Which of the following is a likely consequence of widespread antibiotic resistance in bacteria?

Accepted Answer

Previously treatable infections may become life-threatening due to lack of effective antibiotics.

Question 20

Which of the following best explains why photosynthetic microorganisms are important in the environment?

Accepted Answer

They produce oxygen as a byproduct of photosynthesis, supporting aerobic life.

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