Cell walls and Membranes

Question 1

Gram Stain

Answer 1

Gram Positive (cocci) - purple
Gram Negative (rod) - pink

Question 2

Gram Positive

Answer 2

Cytoplasmic Membrane and Outer peptidoglycan Layer

Question 3

Gram Negative

Answer 3

Cytoplasmic Membrane
Periplasmic space surrounding Peptidoglycan layer
Outer membrane (Lipopolysaccharide and protein)

Question 4

Structure of Peptidoglycan

Answer 4

NAM-NAG Repeating units
Lysozyme sensitive bond
Transpeptidase = enzyme that builds peptide bonds
Penicillin binds to transpeptidase inactivating it and inhibits cell wall synthesis
(Peptide bonds and glycosidic bonds)

Question 5

S-Layers and Capsule

Answer 5

S-Layer - Protein, mono-molecule, variable between species

Capsule - polysaccharide, more common in gram -ve bacteria, virulence factor

Question 6

Archaea

Answer 6

Cell wall = pseudomurein

Membrane = branched isoprene chains, ether linkage, L-glycerol

Question 7

Fungi

Answer 7

Cell membrane - ergosterol

Chitin - N-acetyl-D-glucosamine

Question 8

Antifungal Drugs

Answer 8

Flucytosine - interfere with protein synthesis
Imidazoles - interfere with ergosterol synthesis
Triazoles - “
Polyenes - binds to ergostyrol causing leakage of material
Griseofulvin - binds to keratin precursor making cells resistant to fungal invasion
Candins - Inhibits glucan in fungal cell wall

Question 9

Protozoan parasites - Trypanosoma brucceii

Answer 9

Tsetse fly

Giarda - cyst formation

Question 10

Endospore Formation

Answer 10

1. DNA becomes more dense
2. Developing spore
3. Spore septum grows around protoplast (engulfment)
4. Forespore formation
5. Exosporium appears; primordial cortex is formed between the two membranes
6. Coat layers are formed - Ca2+ incorporation and further dehydration (SASPs, dipicolnic acid)
7. Maturation (resistance to heat and chemicals)
8. Lysis and release of free spore