Bacteria and Cell wall membrane part 3

micrbiology exam 1

what are the major structural features of the gram-positive cell wall?

• primarily composed of peptidoglycan

• wall teichoic acid: anchored to peptidoglycan

• Lipoteichoic acid: anchored to the plasma membrane

• both teichoic acids help maintain gram-positive cell envelope, contribute to negative charge, and help bind host cells to initiate infection

What is the periplasmic space and what are the functions of the proteins within it?

• the region between the plasma membrane and cell wall

• proteins play a role in nutrient acquisition and peptidoglycan synthesis

What is the basic structure of the gram-negative cell envelope?

• outer membrane

• plasma membrane

• thin layer of peptidoglycan

• lipids, lipoproteins, lipopolysaccharides

• periplasmic space

How does the plasma membrane differ from the outer membrane?

The outer membrane has an asymmetrical composition, contains LPS, contains unique porin proteins that act as channels, and contains Braun’s lipoprotein that is a crucial anchor connecting the outer membrane and peptidoglycan cell wall

What is brauns lipoprotein?

a crucial anchor connecting the outer membrane and peptidoglycan cell wall

What are the three major components of lipopolysacchrides?

Lipid A

Core polysaccharide

O antigen

What is the composition of Lipid A?

2 glucosamine sugar derivatives

what is the composition of core polysaccharide?

10 sugar structure joined to Lipid A

What is the structure of O antigen?

polysaccharide that extends outward from the core made of several sugars

what is the major function of LPS?

• contributes to negative charge on cell surface

• helps stabilize outer membrane structure

• host defense protection

• acts as endotoxin

What does lipid A trigger?

Inflammatory cytokine production, an excessive inflammatory response can contribute to vasodilation and decreased blood pressure.

What is the two step process in Gram-Negative transport?

1. the solute crosses the outer membrane into the periplasm

2. then crosses the plasma membrane

transport across outer membrane involves porins - channels allow nutrients and small molecules to pass

what is a hypotonic environment? How is lysis involved with this?

• The concentration outside of the cell is less than inside of the cell

• Without the peptidoglycan layer, the pressure fro the water diffusion would cause the cell to burst (lysis)

What is a hypertonic environment? How is plasmolysis involved with this?

• the concentration outside of the cell is greater than inside

• water leaves the cell and the cytoplasm shrivels up (plasmolysis)

What is lysozome?

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