Question 1

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

Accepted Answer

Prokaryotic cells lack a membrane-bound nucleus, while eukaryotic cells have a membrane-bound nucleus.

Question 2

A patient is diagnosed with a bacterial infection. The bacteria are found to have a thick peptidoglycan layer and teichoic acids in their cell wall. Which type of bacteria is most likely responsible?

Accepted Answer

Gram-positive bacteria

Question 3

Which historical experiment disproved the theory of spontaneous generation by demonstrating that microorganisms do not arise from non-living matter?

Accepted Answer

Pasteur's swan-neck flask experiment

Question 4

A microbiologist is using a light microscope to observe bacteria. What is the primary purpose of staining the bacterial sample before observation?

Accepted Answer

To increase contrast and make cellular structures more visible

Question 5

Which of the following best explains why Gram-negative bacteria appear pink after Gram staining?

Accepted Answer

Their thin peptidoglycan layer does not retain the crystal violet-iodine complex, allowing the safranin counterstain to be visible.

Question 6

Which of the following statements about enzymes is correct?

Accepted Answer

Enzymes lower the activation energy $E_a$ of a reaction, increasing the rate without being consumed.

Question 7

A solution has a pH of 3. Which of the following best describes this solution?

Accepted Answer

It is acidic, with a high concentration of $[H^+]$ ions.

Question 8

Which of the following best describes the function of the bacterial glycocalyx?

Accepted Answer

It helps bacteria adhere to surfaces and protects against desiccation and phagocytosis.

Question 9

A bacterial cell is placed in a hypertonic solution. What is the most likely outcome for the cell?

Accepted Answer

Water will leave the cell, causing it to shrink (plasmolysis).

Question 10

Which of the following best describes the difference between simple diffusion and facilitated diffusion across a cell membrane?

Accepted Answer

Facilitated diffusion requires a membrane protein, while simple diffusion does not.

Question 11

Which of the following is an example of an amphipathic molecule found in cell membranes?

Accepted Answer

Phospholipid

Question 12

A scientist is studying a microbe that can grow in the presence or absence of oxygen, but grows better when oxygen is present. How should this organism be classified?

Accepted Answer

Facultative anaerobe

Question 13

Which of the following best explains the role of ATP in cellular metabolism?

Accepted Answer

ATP stores and transfers energy for cellular processes by hydrolysis of its terminal phosphate group.

Question 14

Which of the following statements about DNA and RNA is correct?

Accepted Answer

In DNA, adenine pairs with thymine ($A::T$), while in RNA, adenine pairs with uracil ($A::U$).

Question 15

Which of the following best describes the function of lipopolysaccharide (LPS) in Gram-negative bacteria?

Accepted Answer

LPS provides structural integrity and acts as an endotoxin.

Question 16

A researcher is studying a protein with a sugar group attached. Which type of conjugated protein is this?

Accepted Answer

Glycoprotein

Question 17

Which of the following best describes the function of bacterial endospores?

Accepted Answer

They allow bacteria to survive harsh environmental conditions.

Question 18

Which of the following is a correct statement about the structure of peptidoglycan?

Accepted Answer

It is composed of repeating units of N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) cross-linked by short peptides.

Question 19

A bacterial culture is growing in a medium with a pH of 9. Which of the following best describes this environment?

Accepted Answer

It is alkaline (basic), with a low concentration of $[H^+]$ ions.

Question 20

Which of the following best explains why enzymes are specific for their substrates?

Accepted Answer

The active site of an enzyme has a unique shape that fits only specific substrate molecules.

Microbiology Exam 1 Study Guide: Key Concepts and Foundations

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