Cell wall structure
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Cell wall structure. I. Function. APrevent cell rupture due to osmotic pressure BProvides Shape CAnchors flagella. II. Clinically important. Site of antibiotic action B. Virulence factor that causes disease. IIIComponents. A. Peptidoglycan B. Peptides and proteins

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Cell wall structure

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Cell wall structure

Cell wall structure


I function

I. Function

APrevent cell rupture due to osmotic pressure

BProvides Shape

CAnchors flagella


Ii clinically important

II. Clinically important

  • Site of antibiotic action

    B. Virulence factor that causes disease


Iii components

IIIComponents

A. Peptidoglycan

B. Peptides and proteins

C. Phospolipids

D. Polysaccharides


Iv what is a peptidoglycan layer

IVWhat is a Peptidoglycan Layer?


Iv what is a peptidoglycan layer1

IVWhat is a Peptidoglycan Layer?

A rigid lattice structure made of long polymer of repeating disaccharide sugars that are bond together by polypeptide chains

  • Polymer of disaccharide sugar

    • Made of alternating N-acetylglucosamine (NAG) and N-acetylmurmic acid (NAM)

    • Form long rods that are refered to as the "carbohydrate backbone”


The peptidoglycan layer cont

The Peptidoglycan Layer (cont.)

  • The carbohydrate backbones are held in place laterally by peptide cross bridges

    • Peptide cross bridge binds NAG

  • The carbohydrate backbones are held together vertically by tetrapeptides

    • Tetrapeptides bind to NAM


Gram positive cell walls

Gram Positive Cell Walls

  • Cell wall is made up of many peptidoglycan layers (very thick and rigid)

  • Contain teichoic acids

    • Lipoteichoic acids spans peptidoglycan layer and links to the plasma membrane.

    • Wall teichoic acid links to peptidoglycan layer.

  • Functions of teichoic acid

    • Movement of cations

    • Suport wall durring cell growth

    • Strong antigenic determinant


Gram negative cell walls

Gram Negative Cell Walls

  • Outer membrane is unique in all of biology. Creates a periplasmic space.

    • Peptidoglycan layer inside the periplasmic space

    • Protein receptors that regulate chemotaxis.


Gram negative cell walls cont

Gram Negative Cell Walls (cont.)

2. Outer membrane composed of

  • Phospholipid bilayer: Protects the cell against antibiotics and other chemicals which attack the peptidoglycan layer

  • Lipopolysaccharide layer:

    • O polysccharide (Strongist antigenic determinant).

    • Lipid A (endotoxin). Extremely toxic in minute amount

  • Porin proteins: Channel by which nutrients and waste pass through the cell wall.

  • Lipoproteins: Proteins that connect the outer membrane and the plasma membrane


Gram stain

Gram Stain

  • Primary stain (crystal violet)

  • Wash

  • Mordant (Iodine)

  • Wash

  • Decolorizer (alchol/ acid wash)

  • Counter stain (Safranin)

  • Gram pos = primary stain sticks (crystal violet)

  • Gram neg. = Primary stain fails to bind. These cells are visualized by adding the counter stain (safranin)


Movement of materials across membranes

Movement of Materials Across Membranes

  • Passive Processes

    • Simple diffusion: movement of molecules from areas of high concentration to area of low concentration.

    • Facilitated diffusion: Molecules combines with a plasma membrane protein called a transporter.

    • Osmosis: The movement of water across a selectively permeable membrane. High concentration to low concentration


Movement of materials across membranes1

Movement of Materials Across Membranes

  • Active Transport: The cell uses energy (ATP) to move substance across the plasma membrane.

    • Moves substance from low concentration to high concentration

    • Depends on transporter protein

    • Group translocation: Substance is altered once it is across the membrane to make it impermeable to the membrane.


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