Bacterial cell wall Flashcards

Question

What is the function of Endospores? (only some species).

Answer 1

Survival in harsh conditions

Answer 2

Various roles in interaction with other bacteria and environment

Answer 3

Extra-chromosomal genetic information

Answer 4

Selective permeability

Answer 5

Support and protection

Answer 6

Protein synthesis

Answer 7

Storage of carbohydrates/Proteins and other substances

Answer 8

Genetic material

Answer 9

Protect the cell from mechanical disruption and from being burst by osmotic pressure Gives the cell is shape and rigidity Essential for viability

Answer 10

Composed of unique components found nowhere else in nature. One of the most important sites antibiotic attack Provide ligands for adherence to host cell receptors and receptor sites for drugs or viruses. Cause symptoms of disease in animals Provide immunological distinction and immunological variation among strains of bacteria

Answer 11

Gram negative and gram positive

Answer 12

Using a very simple method known as the gram stain which was discovered in 1884 by Christian Gram.

Answer 13

Uses two dyes Crystal violet (purple) and Safranin (red), iodine and ethanol –Cells dyed purplefirst –Due to structural differences extraction of iodine/crystal violet complexes from bacterial cells with ethanol is variable –Gram positive cells hold onto purple –This is readily extracted from Gram negative cells, which are counter stained red with safranin –Counter stained Gram positive cells remain purple

Answer 14

Mycobacteria fail to stain because of their unique cell wall structure - Presence of mycolic acids (waxy). - M. tuberculosis (TB) - M.Laprae (Leprosy) - Known as acid fast

Answer 15

The difference in Gram response is in part due to different thickness of a polymer called Peptidoglycan Consists of a linear glycan chain of alternating sugar derivatives linked by B1:4 Glycosidic bonds: - N-acetyglyucosamine (NAG) - N-acetylmuramic acid (NAM) Present in both Gram negative and gram prositive types Gives strength to cell wall

Answer 16

The Peptidoglycan is much more thicker

Answer 17

The Peptidoglycan is much more thin

Answer 18

NAG and NAM Cross-links between other tetrapeptides connect the sheets to form a 3-D, rigid matrix. Forms a scaffold -like giant molecule, the peptidoglycan sac Shape of cell is determined by length of peptidoglycan chains and manner and extent of cross linking.

Answer 19

In Gram-positive cell walls only Acidic polysaccharides- Polymers - Glycerol phosphate - Ribitol phosphate - Length of the chain and the nature and location of the side-chain constituents vary species to species - Up to 50% of the wall may be teichoic acid - Some covalently linked to NAM residues of peptidoglycan- Teichoic acid - Linked to lipids in the plasma membrane- Lipoteichoic acid

Answer 20

Anchorage of the cell wall to the plasma membrane- Lipoteichoic acids. Provides chemical groups that give an over all negative charge Major antigenic determinant of the cell surface

Answer 21

Some peptidoglycan forms a single layered sheet around the cell. - The rest, with minimal cross-linking - Forms, a gel-like substance- the periplasmic gel that fills the periplasmic space. External to the periplasm is a complex outer membrane Reduced Peptidoglycan sac still gives the cell its shape and integrity

Answer 22

Contains proteins with a variety of roles Nutrients acquisition - Hydrolytic enzymes - Binding proteins for solute transport Detoxifying enzymes -Antibiotics (beta lactamase) Enzymes for peptidoglycan synthesis Proteins involved in chemotaxis

Answer 23

Consists of two components - Normal phospholipids - Lipopolysaccharide (LPS) LPS is extermely toxic to humans and other animals and is referred to as an endotoxin - Minute amounts of LPS can produce fever and shock - Promotes cytokine release (IL's) - Gram-negative shock or endotoxic shock

Answer 24

–LPS in the outer membrane results in a barrier * Blocks the passage of most organic molecules into the cell * Including nutrients –Special proteins form pores through the outer membrane called porins * This allows the bacteria count the issue of the barrier * Porinsallow hydrophilic molecules of low MW to diffuse into the periplasm

Answer 25

Separation of a single cell into two identical daughter cells, each containing one copy of the parental DNA.

Answer 26

New cell wall synthesis must take place during cell division so the cell can increase its size –Links in the peptidoglycan must be broken –New peptidoglycan monomers must be inserted –Peptide cross links must be resealed. –Happens in 3 stages

Answer 27

break the glycosidicbonds between the peptidoglycan monomers and break peptide cross-bridges

Answer 28

enzymes insert and link new peptidoglycan monomers into the breaks in the peptidoglycan

Answer 29

enzymes reform the peptide cross-links between the rows and layers of peptidoglycan.

Answer 30

–This is the reaction that antibiotics such as penicillin inhibits –Penicillium (Fungus/Mould –Eukaryotic cell)

Answer 31

–Newly synthesised peptidoglycan cannot be cross linked –New cell wall cannot be made –Resulting in cell lysis

Answer 32

–Stands for Methicillin Staphylococcus aureus –S. aureus is a gram +vebacterium

Answer 33

–Penicillin class beta lactam antibiotic –Like penicillin it kills gram +vebacteria by binding to the ‘PBP’ blocking peptidoglycan synthesis –Resistance to penicillin occurs when bacteria produce beta lactamases –However > Methicillin is resistant to beta lactamase –Resistance to methicillin occurs through a mutation to the PBP