4 - Prokaryotic structure and function 2

Question 1

What are the proteins contained in the periplasm involved in

Answer 1

1. Nutrient acquisition
2. Peptidoglycan biosynthesis
3. Protein folding
   4.Contact dependent stress response systems
4. Synthesis of pili and flagella

Question 2

What two sugars make up cell walls (peptidoglycan)

Answer 2

Two alternating disaccharides:
- NAM (N-acetylmuramic acic)
- NAG (N-acetylglucosamine)

Question 3

Stem peptide

Answer 3

Each glycan dimer is attached to a pentapepide (5 amino acids) this joins peptides

Question 4

Glycan

Answer 4

Long strands of repeating sugar units

Question 5

How is the NAG - NAM dimer connected

Answer 5

Beta - (1,4) - glycosidic bonds to form a long polymer

Question 6

How are peptidoglycan strands linked

Answer 6

Crosslinked to each other by covalent bonds between the stem peptides. Can be direct (gram negative) or indirect (gram positive) using peptide inter bridge

Question 7

Teichoic acid (+)

Answer 7

A polymer of glycerol or ribitol joined by phosphate groups. Unique to gram positive cell walls and negatively charged. Connected covalently to peptidoglycan and cytoplasmic membrane

Question 8

Roles of teichoic acid

Answer 8

1. Help maintain peptidoglycan structure,
2. cell division
3. protect against harmful substances (anti biotics)
4. major inflammatory mediator

Question 9

Bacteria outer membrane (-)

Answer 9

Unique to gram negative bacteria. Asymmetric bilayer. Contains Outer Membrane Proteins (OMPs)

Question 10

Explain the asymmetric bilayer of the outer membrane

Answer 10

• Inner leaflet phospholipids and proteins (Braun’s lipoprotein)
• Outer leaflet 70% glycolipid (Lipopolysaccharides)
• Negatively charged
• Essential for life
• Endotoxin - simplitates immune cells (lipid A portion)

Question 11

Function of the outer membrane and outer membrane channels

Answer 11

• Connect periplasm to environment
• Porins (form channels)
• Transport of nutrients
• Secretion of proteins

Question 12

Mycobacterial cell wall

Answer 12

• Gram positive
• Thin layer of peptidoglycan surrounded by mycolic acid layers.
• Waxy, hydrophobic, high lipid content.
• Function: permeability and fluidity. Allows to thrive air water interfaces

Question 13

How are Mycobacterium stained

Answer 13

Ziehl-Neelsen or Kinyoun’s stain

Question 14

Archaea plasma membrane

Answer 14

• Composed of branched chain hydrocarbons attached to glycerol by ether links.
• Can be monolayer (C40 tetraether lipid) or bilayer (C20 diether lipid)

Question 15

Special characteristic of archaea monolayer plasma membrane

Answer 15

More rigid and resist extreme heat

Question 16

Archaea cell wall

Answer 16

Many different types (no peptidoglycan present). Can stain positive or negative

Question 17

Gram negative Archaea cell wall stain

Answer 17

1 or 2 S-layers (20-40 nm) above cell membrane
Interlocking protein units

Question 18

Gram positive Archaea cell wall stain

Answer 18

Made up of Pseudomurein, Not sensitive to penicillin or lysozyme

Question 19

Bacteria external structures

Answer 19

• Capsules
• Slime Layers
• Sheaths and Prostheca
• Pili / Fimbriae, Flagella

Question 20

Roles of bacterial ecternal structures

Answer 20

Protection from the environment, Adhesion, Motility

Question 21

Capsule

Answer 21

Organised matrix firmly anchored to cell

Question 22

Slime layer

Answer 22

Diffuse, disorganised matrix, easily removed

Question 23

composition of capsules and slime layers

Answer 23

Polysaccharides (majority) and Poly amino acid

Question 24

role of capsules and slime layers

Answer 24

1. Resist phagocytosis, 2.Protection from desiccation,
2. Adherence,
3. Gliding motility (slime layer)

Question 25

Sheaths

Answer 25

Stiff polysaccharide tube containing cells. Function: Attach to solid surfaces Protection from protozoan predators Sieve for acquiring nutrients

Question 26

Prosthecae

Answer 26

Extensions containing cell wall and plasma membrane. Function: Attach to solid surfaces

Question 27

Pili/Fimbriae

Answer 27

Short, fine, hair-like appendages, Hollow brittle tube Consisting of multiple pilin subunits organised as a helix

Question 28

how are types of pili defined

Answer 28

Types I-IV defined by Length, Diameter of the fibre and Location on the cell (Polar, Peritrichous, Single, multiple)

Question 29

Function of pili/fimbriae

Answer 29

1. Adherence 2. Twitching motility 3. Gliding motility

Question 30

Sex pillus

Answer 30

Larger than other pili, transfer of DNA from host to recipient. Conferred by a conjugative plasmid (not encoded on host nucleoid)

Question 31

Role of sex pillus

Answer 31

Exchange of genetic content, spread of antibiotic resistance on R plasmids

Question 32

Flagella

Answer 32

Longer hair like appendage consisting of a hollow filament composed of flagellin protein, hook, basal body. Basal motor structure drives rotation of flagellum (act as propeller)

Question 33

Role of flagella

Answer 33

Swimming in aqueous environments and seeking nutrients (chemotaxis)

Question 34

What is chemotaxis (Tumbling)

Answer 34

The movement of cells or organisms in response to chemical gradients in their environment.

Question 35

Positive chemotaxis

Answer 35

Movement towards a higher concentration (attractant)

Question 36

Negative chemotaxis

Answer 36

Movement towards decreasing concentration (repellent)

Question 37

Name two alternate cell structures

Answer 37

Endospores and Conidiospores

Question 38

Endospores

Answer 38

Produced by a small number of bacteria (eg Bacillus), can be terminal (end), subterminal (just before end) or central (middle)

Question 39

Characteristics of endospores

Answer 39

Dormant, resist extreme conditions which would kill the vegetative cell (eg. starvation, heat, salt) and core contains dipicolinic acid

Question 40

Sporulation

Answer 40

Occurs in response to limited carbon, nitrogen, phosphorus. Endospore germination occurs in favourable conditions to become vegetative cell

Question 41

What are the steps of sporulation

Answer 41

1. Asymmetrical cell division 2. Engulfment of forespore 3. Cortex and coat synthesis 4. Endospore maturation, 5. Sporangium lysis

Question 42

Conidiospores

Answer 42

Produced by Streptomyces in response to nutrient starvation. Thin wall spores at the end of filaments. Resistant to desiccation but not heat.

Question 43

Periplasm

Answer 43

Located: Gram -tve Space between the Outer membrane and the Inner membrane

Question 44

What are Sheaths made from

Answer 44

Ferric or Manganic Oxides

Question 45

Attachment locations of Flagella

Answer 45

Polar- protruding from one end Peritrichous - protruding from uniform points across the bacterial surface Mono- or multiple

Question 46

Axial filaments

Answer 46

- Specialised flagella that are trapped inside the periplasm of gram negative cell walls - Arranged in a helical shape

Question 47

Axial filaments Function

Answer 47

Function for locomotion – Corkscrew through liquid – Crawl on surfaces

Question 48

Endospore Structure

Answer 48

Ribosomes DNA Core wall Cortex Spore coat Exosporium

Question 49

Compare the archaeal cell wall to Gram positive and Gram negative bacterial call walls.

Question 50

Describe the features of the cell wall of Mycobacteria and explain why this organism is Gram positive.

Question 51

Compare the structure and functions of pili and flagella.

Question 52

What are capsules and slime layers and what functions do they perform?

Question 53

Describe endospore formation. What are the characteristics of endospores?

Question 54

Compare a Gram negative cell wall to Mycobacterial cell walls.

Question 55

List four features of an endospore and describe the sporulation cycle of endospores using a diagram.