Chapter 2: Microbial Cell Structure and Function

cytoplasmic membrane

surrounds cytoplasm and separates it from the environment; mixture of macromolecules and small molecules

What is the main function of the cytoplasmic membrane?

selective permeability (nutrients transported in and waste products out);

membrane proteins facilitate these rxns and function in energy metabolism

What are the 3 functions of the cytoplasmic membrane?

1. permeability barrier

2. protein anchor

3. energy conservation

Bacterial cell membranes have (ester/ether) linkages.

ester

Archaeal cell membranes have (ester/ether) linkages.

ether

Bacterial cell membranes have (fatty acids/phytanyl).

fatty acids

Archaeal cell membranes have (fatty acids/phytanyl).

phytanyl

Bacterial cell membranes have a phospholipid (bilayer/monolayer).

bilayer

Archaeal cell membranes have a phospholipid (bilayer/monolayer).

bilayer or monolayer

Is the cell wall selectively permeable?

permeable, but not selective

What are the functions of the cell wall?

• withstanding osmotic/turgor pressure to prevent cell lysis

• maintaining cell shape and rigidity

Most Bacteria are separated into two groups based on…

Gram stain (organization and cell wall structures)

Peptidoglycan is only in ____ cell walls.

bacterial

What is the structure of the repeating unit in peptidoglycan?

alternating NAG and NAM with glycosidic bonds in between

What is the glycosidic bond broken by?

lysozyme

Archaea are resistant to ____.

lysozyme

What are the structural differences between Gram + and Gram - cell walls?

Gram +:

• thick block of peptidoglycan

• wall teichoic acid

• lipoteichoic acid

Gram -:

• outer membrane layer

• thin layer of peptidoglycan

• lipopolysaccharides (LPS)

• porin proteins

• lipoproteins

What are the structural similarities between Gram + and Gram - cell walls?

• peptidoglycan

• periplasmic space

• cell membrane

• membrane proteins

Most of the cell wall is composed of…

outer membrane or the lipopolysaccharide (LPS) layer

What replaces most of the phospholipids in the outer half of the outer membrane?

LPS

endotoxin

lipid A; the toxic component of LPS

What is the toxic component of LPS?

lipid A

Endotoxins are only in Gram (+/-).

-