Question 1

A patient develops a severe infection after a hip replacement surgery. Laboratory analysis reveals the presence of a thick, persistent bacterial community on the surface of the prosthesis. Which of the following best explains why this infection is particularly difficult to treat with antibiotics?

Accepted Answer

Biofilms provide a protective matrix that increases bacterial resistance to antibiotics by up to 1000-fold.

Question 2

Which of the following statements correctly distinguishes between gram-positive and gram-negative bacterial cell walls?

Accepted Answer

Gram-positive bacteria have a thick peptidoglycan layer and teichoic acids, while gram-negative bacteria have a thin peptidoglycan layer and an outer membrane with lipopolysaccharides.

Question 3

A researcher is studying a bacterial strain that can survive extreme heat and chemical exposure. Which structure is most likely responsible for this resistance?

Accepted Answer

Endospore

Question 4

Which of the following best describes the function of the sodium–potassium pump in animal cells?

Accepted Answer

It uses ATP to move three sodium ions out of the cell and two potassium ions into the cell, maintaining membrane potential.

Question 5

A mutation in a bacterial gene results in the insertion of a single nucleotide base. What is the most likely consequence of this mutation?

Accepted Answer

A frameshift mutation, which alters the reading frame and can produce a nonfunctional protein.

Question 6

During aerobic cellular respiration, what is the net yield of ATP molecules produced from one molecule of glucose in prokaryotic cells?

Accepted Answer

$$38$$

Question 7

Which of the following best explains why sulfonamide antibiotics selectively inhibit bacterial growth without harming human cells?

Accepted Answer

Sulfonamides inhibit the synthesis of folic acid, which bacteria must synthesize but human cells obtain from their diet.

Question 8

A scientist observes a eukaryotic cell with numerous rough endoplasmic reticulum (rER) and a prominent Golgi apparatus. Which function is this cell most likely specialized for?

Accepted Answer

Synthesis and secretion of proteins

Question 9

Which of the following processes is responsible for the movement of water from a hypotonic environment into a bacterial cell, potentially causing it to swell?

Accepted Answer

Osmosis

Question 10

A bacterial cell is exposed to a competitive inhibitor that resembles the substrate for a key metabolic enzyme. Which of the following best describes how this inhibitor affects enzyme activity?

Accepted Answer

It binds to the active site, preventing the substrate from binding and thus reducing enzyme activity.

Question 11

Which of the following best describes the role of tRNA during translation?

Accepted Answer

tRNA carries amino acids to the ribosome and matches its anticodon to the codon on mRNA.

Question 12

A scientist is studying a bacterium that can transfer antibiotic resistance genes to other bacteria through direct cell-to-cell contact. Which genetic transfer mechanism is being observed?

Accepted Answer

Conjugation

Question 13

Which of the following is a key difference between prokaryotic and eukaryotic cells?

Accepted Answer

Eukaryotic cells have a nucleus containing their DNA, while prokaryotic cells have a nucleoid region without a membrane.

Question 14

Which of the following best describes the process of semiconservative DNA replication?

Accepted Answer

Each new DNA molecule consists of one original (parental) strand and one newly synthesized strand.

Question 15

A cell is placed in a solution containing a higher concentration of solutes than the cell's cytoplasm. What will most likely happen to the cell?

Accepted Answer

Water will move out of the cell, causing it to shrink (crenate).

Question 16

Which of the following correctly matches a metabolic pathway with its primary function?

Accepted Answer

Glycolysis: Conversion of glucose to pyruvic acid with a net gain of 2 ATP.

Question 17

Which of the following best explains why antibiotics that target 70S ribosomes are effective against bacteria but not human cells?

Accepted Answer

Bacterial ribosomes are 70S, while human cytoplasmic ribosomes are 80S, allowing selective targeting.

Question 18

A plant cell is observed to have a large central vacuole, chloroplasts, and a cell wall. Which of the following statements is true regarding these structures?

Accepted Answer

The central vacuole stores water and helps maintain cell turgor pressure.

Question 19

During which phase of the eukaryotic cell cycle does DNA replication occur?

Accepted Answer

S phase

Question 20

Which of the following best describes the main significance of meiosis in sexually reproducing organisms?

Accepted Answer

It reduces the chromosome number by half and increases genetic diversity through recombination.

Cell Structure, Function, and Genetics: Microbiology Study Guide

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