Microbiology: Cell Structure and Function Flashcards

Why do viruses not possess ribosomes or metabolic enzymes of their own?

Answer: Viruses are obligate intracellular parasites that hijack host cell machinery for replication

Viruses are acellular obligate intracellular parasites that depend entirely on host ribosomes, enzymes, and metabolic pathways to replicate their genomes and synthesize proteins.

Which statement about inclusion bodies in bacterial cells is MOST accurate?

Answer: They are intracellular deposits of storage polymers or crystals that serve as nutrient reserves

Inclusion bodies are intracellular aggregates of storage compounds (glycogen, polyhydroxybutyrate, sulfur globules) or crystalline proteins that cells accumulate under nutrient excess or stress conditions.

A coccus (spherical bacterium) that divides in multiple planes and forms a cube-shaped packet of 8 cells is called a:

Answer: Sarcina

Sarcina refers to a packet of 8 cocci arranged in a cube, resulting from division in three perpendicular planes.

The outer leaflet of the gram-negative outer membrane is composed primarily of which molecule?

Answer: Lipopolysaccharide (LPS)

The outer leaflet of the gram-negative outer membrane is almost entirely composed of lipopolysaccharide (LPS), which serves as a barrier and is recognized by the host immune system.

How does the chemical nature of archaeal cell walls differ from the peptidoglycan of bacteria?

Answer: Many archaea have pseudopeptidoglycan containing N-acetyltalosaminuronic acid or entirely different polymers, lacking muramic acid

Archaea that have walls use pseudopeptidoglycan (with N-acetyltalosaminuronic acid replacing muramic acid) or other polymers (S-layers, polysaccharides), none of which contain the N-acetylmuramic acid diagnostic of bacterial peptidoglycan.

Which term describes the region between the outer and inner membranes of gram-negative bacteria where peptidoglycan is located?

Answer: Periplasmic space

The periplasmic space (periplasm) is the compartment between the inner (cytoplasmic) membrane and the outer membrane of gram-negative bacteria, housing the thin peptidoglycan layer.

A helical bacterium with a flexible cell body and internal flagella (axial filaments) located in the periplasmic space is classified as a:

Answer: Spirochete

Spirochetes are distinguished by their periplasmic flagella (endoflagella) that wind around the protoplasmic cylinder inside the outer membrane sheath, producing their characteristic corkscrew motility.