Lec 4: Prokaryotic structure and function

Question 1

Periplasm

Answer 1

Proteins involved in:

Nutrient acquisition

Peptidoglycan biosynthesis

Protein folding

Contact dependent stress response systems

Synthesis of pili and flagella

Question 2

Teichoic acid

Answer 2

Polymers of glycerol/ribitol joined by phosphate groups

-vely charged

Connected covalently to peptidoglycan & cytoplasmic membrane

Question 3

Outer membrane

Answer 3

Asymmetric bilayer: inner leaflet (phospholipids and proteins), outer leaflet (glycolipid)

Outer membrane proteins: connect periplasm to environment

Question 4

Mycobacterial cell wall

Answer 4

Gram positive

Thin layer of peptidoglycan surrounded by mycolic acid

Waxy, hydrophobic, high lipid content

Permeability and fluidity

Question 5

Archaea plasma membrane

Answer 5

Branched chain hydrocarbons attached to glycerol by ether links

Monolayer: more rigid, resist extreme hear

Bilayers

Question 6

Archaea cell wall

Answer 6

No peptidoglycan

Gram -ve: S-layer above membrane

Gram +ve: pseudomurein, chondroitin sulfate, other heteropolysaccharide

Question 7

Bacteria external structures

Answer 7

Capsules, slime layers, sheaths & prosthecae, pili/fimbriae, flagella

Protection from environment, adhesion, motility

Question 8

Capsules and slime layers

Answer 8

Capsule: organised matrix anchored to cell

Slime layer: diffuse, disorganised matrix, easily removed

Polysaccharides, poly AA

Resist phagocytosis, protection from dessication, adherence, gliding motility

Question 9

Sheaths

Answer 9

Stiff polysaccharide tube containing cells

Attach to solid surfaces, protection from protozoan predators, sieve for acquiring nutrients

Question 10

Prosthecae

Answer 10

Extensions containing cell wall and plasma membrane

Attach to solid surface

Question 11

Pili/ fimbriae

Answer 11

Short, fine, hair-like appendages

Hollow brittle tube

Consists of multiple pilin subunits -> organised as helix

Adherence, twitching and gliding motility

Question 12

Sex pilus

Answer 12

Larger than other pili

Transfer of DNA from host bacteria to recipient

Conferred by plasmid

Conjugative plasmid

Role: exchange of genetic content, spread of antibiotic resistance on R plasmids

Question 13

Flagella

Answer 13

Filament - hook - basal body

Hollow filament composed of flagellin protein

Basal motor -> rotation of flagellum (acts like propeller)

Role: swimming in aqueous environments, seek nutrients (chemotaxis)

Question 14

Flagella: axial filaments

Answer 14

Spirochetes

Gram -ve

Periplasmic flagella organised as axial filaments

Locomotion: corkscrew through liquid, crawl on surfaces

Question 15

Endospores

Answer 15

Distribution: produced by small no. of bacteria

Structure: exosporium, spore coat, cortex, core wall, ribosomes and dna

Question 16

Endospore characteristics

Answer 16

Resist extreme conditions

Core contains dipicolinic acid

Question 17

Sporulation

Answer 17

1. Spore septum isolated newly replicated DNA & portion of cytoplasm
2. Plasma membrane surrounds DNA, cytoplasm & membrane in 1.
3. Spore septum surrounds isolated portion -> forespore
4. Peptidoglycan layers forms between membranes
5. Spore coat forms
6. Endospore freed from cell

Question 18

Conidiospores

Answer 18

Distribution: produced streptomyces (response to nutrient starvation)

Structure: thin wall spires at end of filaments

Characteristics: resistant to desiccation but not hear