Prokaryotic Cell Structure and Function

Question 1

Describe the primary function of the cell membrane

Answer 1

permeability barrier between the cellular contents and the extraenous evironment, preventing leakage

Question 2

Describe secondary function of the cell membrane

Answer 2

transportation of cellular inputs and outputs, such as nutrients, or toxic metabolic products, respectively

Question 3

Describe tertiary function of the cell membrane

Answer 3

provides a protein achor, for which proteins can capitalise in order to fufill their repsective transportative, bioenergetic and chemotactic functions

Question 4

Describe a function of cell membranes specific to unicellular organisms

Answer 4

energy conservation, as the site of generation and dissipation of the proton motive force in respiration

Question 5

Describe the generalities of unicellular cell wall

Answer 5

composed of peptidoglycan (murein)

Question 6

Describe peptidoglycan

Answer 6

• aka murein
• glycan tetrapeptide composed of repeating amino suagrs of N-acetylglucosamine and N-acetylmuramic acid, L-alanine, L-lysine, D-glutamic acid, diaminopimelic acid (DAP) and D-alanine
• contains a lysozyme-sensitive glycosidic bond

Question 7

Describe the characteristics of a Gram positive cell wall in bacteria

Answer 7

• much thicker peptidoglycan layer (taking up to 90% of the cell wall’s composition) arranged in cross-linked cables
• variable glycine interbridge between D-alanine and L-lysine
• various protruding acid components

Question 8

List some of the protruding acid components of Gram positive cell walls in bacteria

Answer 8

• teichoic acid (glycerol or ribitol-phopsphate)
• lipoteichoic acid

Question 9

Describe the cell wall of Staphylococcus aureus

Answer 9

• Gram-positive
• interbridge is 5 glycine residues long

Question 10

Describe the characteristics of a Gram-negative bacterial cell wall

Answer 10

• outer membrane
• peptide crosslinker between DAP and D-Alanine
• components are made up of Lipid A , Core polysaccharide and O-specific polysaccharide segments
• as necessitated by the presence of two membranes, there is periplasm space in between

Question 11

Describe Lipid A

Answer 11

a non-glycerol-lipid saccharide of glucosamine phosphate

Question 12

Describe Lipopolysachharides

Answer 12

• endotoxins
• result in sicknesses such as diarrhoea
• eg. Lipid A

Question 13

Describe the periplasm space

Answer 13

• site for enzyme and protein binding
• contains porins

Question 14

What are porins (in the periplasm space of Gram negative bacterial cell walls)

Answer 14

protein trimers that form solute pores

Question 15

Describe cell walls of Methanobacterial archaea

Answer 15

• Pseudomurein compound

Question 16

Describe Psuedomurein

Answer 16

• lysozyme insensitive bond (B1,3; as opposed to B1,4)
• N-Acetyltalosaminuronic acid element
• retains its N-acetylglucosamine component and peptide crosslinkers
• most commonly arranged in S-layer

Question 17

Describe the polysaccharide capsule

Answer 17

• outside the murein cell wall
• extensive and strongly attached slime layer
• can be perceived under staining with India ink

Question 18

List the motile elements of bacteria outside of the cell wall

Answer 18

• flagella
• fimbriae
• pilli

Question 19

What are fimbriae?

Answer 19

very short protein filaments

Question 20

What is the archaeal equivalent of a pillus?

Answer 20

• the Hami
• microscopic grappling hook, intended for the functional of cell attachment into a biofilm
• for nutrient acquisition in benthic arenas

Question 21

Describe the bacterial cell membrane

Answer 21

• 6-8nm in diameter
• phospholipid bilayer
• both integral and peripheral membrane proteins that complete a variety of functions
• strengthened by hopanoid, not sterol compounds

Question 22

Describe the archaeal cell membrane

Answer 22

• can be unilayered as well as bilyarered
• ether, rather than ester bonds, joining the glycerophopshate groups to their fatty acid chains
• contain proteinous elements

Question 23

Describe the fatty acid chains of archaeal cell membranes

Answer 23

composed of isopropene-derived compounds

Question 24

Describe the isopropene-derived compounds that make up the fatty acid chains of archaeal cell membranes

Answer 24

• phytanyl
• biphytanyl
• sometimes crenarchaeol, in unilayered membranes

Question 25

Describe the functions of the pills

Answer 25

- HGT - transfer attenuated viruses from bacteria to bacteria to aid immunity

Question 26

Describe storage polymers in bacterial cells

Answer 26

- polyhydroxybutyrate - polyphosphate - elemental sulfure storage granules

Question 27

Describe polyhydroxybutyrate in bacterial cells

Answer 27

- acetyl-coA derived storage polymer - carbon storage

Question 28

Describe polyphosphate in bacterial cells

Answer 28

- ATP-derived storage polymer - phosphorus and energy storage - can produce ATP on hydrolysis

Question 29

Describe elemental sulfur storage granules in bacterial cells

Answer 29

found in purple photosynthetic S bacteria

Question 30

Describe B & C magnetosomes

Answer 30

- cell membrane structure - found in magnetotactic bacteria - detect the magnetic pole of the Earth, allowing vertical bacteria migration down to lower oxygen concentrations

Question 31

How can magnetosomes detect the magnetic pole of the Earth?

Answer 31

Because the contain iron magnetite

Question 32

Describe gas vacuoles in bacterial cells

Answer 32

- allow bacteria to undergo density adjustments - allowing vertical migration through water columns

Question 33

Describe the flagellum

Answer 33

- 4 ring structure, hook and helical fiament - L ring; P ring; MS ring and the C ring - can take many structures

Question 34

Describe the flagella L ring

Answer 34

found within the LPS segment of the cell wall

Question 35

Describe the flagella P ring

Answer 35

found in the peptidoglycan

Question 36

Describe the flagella MS ring

Answer 36

in the membrane

Question 37

Describe the flagella C ring

Answer 37

in the cytoplasm

Question 38

Describe the flagella structure found in Salmonella and Escherichia coli bacteria

Answer 38

the radial peritrichous

Question 39

Describe potential flagella forms

Answer 39

- radial peritrichous - lateral polar - singular tuft-like lophotrichous - double tuft-like amphitricous

Question 40

Describe the primary function of flagella

Answer 40

motility – rotation of the flagellum can result in both bidirectional (reversing) and unidirection (cessation) movement

Question 41

How is flagella rotation achieved?

Answer 41

Mot proteins receives energy from chemiosmotic proton flow, allowing rotation of the entire basal body

Question 42

What are the motor proteins referred to as

Answer 42

- Mot - a stator

Question 43

Describe flagellum assembly

Answer 43

- must grow outwards from the bacterial cytoplasmic base - from the MS and C rings, to the Mot proteins, to the P ring, L ring, early hook, Capped late hook, the hook-filament junction and finally the filament itself - during assembly flagellin can migrate through the core of the flagellum, allowing assembly of the tip and the filament

Question 44

Describe flagellin

Answer 44

proteinous monomer

Question 45

Describe the core of the flagellum

Answer 45

hollow

Question 46

Describe the archaeal flagellum equivalent

Answer 46

- archaellum - half the width of a bacterial flagellum - uses ATP to rotate

Question 47

Describe archaellum assembly

Answer 47

FlI and FlaX external and FlaJ rotary motor proteins, which roatte the filament

Question 48

Describe the archaellum filament

Answer 48

protrudes from the S-layer membrane

Question 49

Describe the secondary function of flagella and archaella

Answer 49

- faciliation of chemotaxis - walking is biased by chemical gradients over time

Question 50

Describe the method of walking in flagella and archaella

Answer 50

- random in three dimensions - both running and tumbling

Question 51

Describe the flagella of Spirochaetes Treponema pallidum and Borrellia burgdorferi

Answer 51

rigid endoflagella inside the flexible outer sheath, in the periplasm space

Question 52

Describe the structure of endoflagella

Answer 52

attached to one end of the protoplasmic cylinder

Question 53

Describe the protoplasmic cylinder

Answer 53

generally helical

Question 54

Describe endoflagella rotation

Answer 54

- directly results in sheath rotation - corkscrew action - allows for crossing of bodily mucus membranes

Question 55

What is the contrivance of endoflagella

Answer 55

crossing of bodily mucus membranes of supreme importance to pathogenic, parasitic bacteria

Question 56

Describe gliding motility in bacteria and archaea

Answer 56

slime, or pilli-mediated pulling forces

Question 57

Describe gliding motility in Flavobacterium johnsoniae

Answer 57

- gliding proteins released from the cell surface - pulling force in antithesis to the cell motion - requires a proton motive force

Question 58

Describe swarming behaviours in bacteria

Answer 58

- mediated via the pilli - when bacteria exist on surfaces

Question 59

Describe retractile spores in bacteria

Answer 59

- thermo-, osmo- and chemical resilience - death will only occur at typically 121 degrees Celsius

Question 60

Describe the structure of bacterial retractile spores

Answer 60

- exosporium outside the spore coat, itself outside of the core wall - inside of this is the cortex and finally the DNA

Question 61

Describe the physiology of bacterial retractile spores

Answer 61

- very little water - internal pH is one unit lower than that of its parent vegetative cell

Question 62

Why do bacterial retractile spores exhibit slightly acidic pH

Answer 62

- high volume of constituent dipicolonic acid - small acid soluble spore proteins

Question 63

Describe the formation of bacterial retractile spores

Answer 63

- during germination of a vegetative cell - assymetric cell division of vegetative cells post-growth is the commitment to sporulation Stage I

Question 64

Describe Stage II of bacterial retractile sporulation

Answer 64

- pre-endospore forms within the vegetative mother cell - cell becomes septated

Question 65

Describe Stage III of bacterial retractile sporulation

Answer 65

- endospore becomes engulfed - cell is now sporulating cell

Question 66

Describe Stage IV of bacterial retractile sporulation

Answer 66

- formation and differentiation of the cortex, cell wall and cytoplasmic membrane

Question 67

Describe Stage V of bacterial retractile sporulation

Answer 67

- formation of the spore coat - uptake of calcium ions, SASps and the dipicolinic acid - gives the spore its lower pH

Question 68

Describe Stage VI of bacterial retractile sporulation

Answer 68

results in maturation

Question 69

Describe Stage VII of bacterial retractile sporulation

Answer 69

results in cell lysis, and mature endospore release