AP-Micro Microbiology: Cell Structure and Function 3

Question 1

Endospores produced by Bacillus and Clostridium species are extraordinarily resistant to heat. Which component is MOST responsible for this resistance?

Accepted Answer

Dipicolinic acid chelated with calcium ions

Answer

Dipicolinic acid (DPA) complexed with calcium ions replaces water in the spore core and stabilizes proteins and DNA against heat denaturation.

Question 2

Which eukaryotic cell structure is thought to have originated from an ancestral proteobacterium based on endosymbiotic theory?

Accepted Answer

Mitochondrion

Answer

Mitochondria are believed to have evolved from an alpha-proteobacterial endosymbiont, supported by evidence such as their own circular DNA, 70S ribosomes, and binary fission-like replication.

Question 3

What distinguishes S-layer proteins from other bacterial surface structures?

Accepted Answer

They form a two-dimensional crystalline array covering the cell surface

Answer

S-layers are paracrystalline protein or glycoprotein arrays that self-assemble into a regular 2D lattice over the entire cell surface of many bacteria and archaea.

Question 4

A bacterium lacking a functional sec (secretion) pathway would MOST likely fail to:

Accepted Answer

Translocate proteins across or into the cytoplasmic membrane

Answer

The Sec pathway is the primary general secretion system responsible for translocating unfolded proteins across the cytoplasmic membrane to the periplasm or cell surface.

Question 5

Teichoic acids are a defining component of which type of bacterial cell wall?

Accepted Answer

Gram-positive peptidoglycan layer

Answer

Teichoic acids are anionic polymers (wall teichoic acids and lipoteichoic acids) embedded in the thick peptidoglycan of gram-positive bacteria, contributing to surface charge and ion regulation.

AP Practice Test

AP Practice Test

AP-Micro Microbiology: Cell Structure and Function 3