Question 1

Which of the following statements best explains why Gram-negative bacteria are generally more resistant to antibiotics than Gram-positive bacteria?

Accepted Answer

Gram-negative bacteria possess an outer membrane containing lipopolysaccharides (LPS) that acts as a barrier to many antibiotics.

Question 2

A microbiologist is attempting to identify a bacterial sample using a Gram stain. After staining, the cells appear pink under the microscope. What can be inferred about the cell wall structure of these bacteria?

Accepted Answer

They have a thin peptidoglycan layer and an outer membrane containing LPS.

Question 3

Which of the following best describes the process of oxidative phosphorylation in microbial metabolism?

Accepted Answer

ATP is generated as electrons are passed through the electron transport chain, creating a proton gradient used by ATP synthase.

Question 4

A patient is infected with a bacterium that survives harsh conditions by forming endospores. Which genus is most likely responsible for the infection?

Accepted Answer

Bacillus

Question 5

Which of the following correctly matches the microbial structure with its primary function?

Accepted Answer

Pilus – conjugation

Question 6

A scientist wants to observe the detailed surface structure of a virus particle. Which microscope should they use and why?

Accepted Answer

Electron microscope, because it uses electrons and heavy metals to achieve millions of folds of magnification.

Question 7

Which of the following equations correctly represents the relationship between nanometers, micrometers, and millimeters?

Accepted Answer

$$1000\ \mathrm{nm} = 1\ \mu\mathrm{m} = 0.001\ \mathrm{mm}$$

Question 8

Which of the following best describes the role of the Calvin-Benson cycle in photosynthetic organisms?

Accepted Answer

It uses ATP and NADH to fix carbon dioxide into organic molecules.

Question 9

A bacterial culture is grown on a medium that only allows Gram-negative bacteria to grow and turns pink if lactose is fermented. What type of medium is this?

Accepted Answer

Selective and differential

Question 10

Which of the following statements about enzyme inhibition is correct?

Accepted Answer

Competitive inhibitors resemble the substrate and compete for the active site.

Question 11

A bacterium is classified as a chemoheterotroph. Which of the following best describes its energy and carbon sources?

Accepted Answer

Energy from chemicals, carbon from organic molecules

Question 12

Which of the following best explains why biofilms are problematic in medical settings?

Accepted Answer

Biofilms protect microbes from antibiotics and the immune system, making infections harder to treat.

Question 13

A microbiologist wants to estimate the number of viable bacteria in a water sample. Which method would provide a direct count of living cells?

Accepted Answer

Plate count method after serial dilution

Question 14

Which of the following statements about prokaryotic and eukaryotic cells is correct?

Accepted Answer

Prokaryotic cells lack a nucleus and organelles, and have a single circular chromosome.

Question 15

A bacterium is placed in a solution with a higher solute concentration than its cytoplasm. What is the most likely outcome?

Accepted Answer

Water will leave the cell, causing plasmolysis.

Question 16

Which of the following best describes the process of binary fission in bacteria?

Accepted Answer

One bacterium divides into two genetically identical daughter cells.

Question 17

Which of the following is a correct sequence of events in aerobic respiration?

Accepted Answer

Glycolysis $$\rightarrow$$ Krebs cycle $$\rightarrow$$ Electron transport chain

Question 18

A bacterial cell is exposed to a chemical that disrupts its plasma membrane. Which of the following processes would be most directly affected?

Accepted Answer

Selective transport of molecules into and out of the cell

Question 19

Which of the following best explains why Mycobacterium species require an acid-fast stain for identification?

Accepted Answer

Their cell walls contain mycolic acids that resist decolorization by alcohol.

Question 20

Which of the following statements about the endosymbiotic theory is correct?

Accepted Answer

It proposes that eukaryotic organelles such as mitochondria originated from engulfed prokaryotic cells.

Microbiology Exam 1 Study Guide: Foundations, Cell Biology, Metabolism, Growth, and Control

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