AP-Micro Bacterial Classification 2

Question 1

Which bacterial structure is the primary target of the Gram stain procedure?

Accepted Answer

Peptidoglycan cell wall

Answer

The Gram stain differentiates bacteria based on the thickness of their peptidoglycan cell wall.

Question 2

Bacteria classified as obligate anaerobes would be killed by exposure to which condition?

Accepted Answer

Molecular oxygen

Answer

Obligate anaerobes lack the enzymes needed to detoxify reactive oxygen species, so oxygen is lethal to them.

Question 3

Which of the following best describes the classification of Mycobacterium tuberculosis?

Accepted Answer

Acid-fast bacillus

Answer

Mycobacterium tuberculosis stains acid-fast due to its waxy mycolic acid-rich cell wall rather than staining in a typical Gram reaction.

Question 4

A bacterium that grows optimally at temperatures between 20°C and 45°C is classified as a:

Accepted Answer

Mesophile

Answer

Mesophiles thrive at moderate temperatures (20–45°C) and include most human pathogens.

Question 5

Which feature distinguishes Archaea from Bacteria at the molecular level?

Accepted Answer

Ether-linked membrane lipids

Answer

Archaea have ether-linked lipids in their membranes, whereas Bacteria have ester-linked lipids.

AP Practice Test