Lecture 3 - Cell Structure and Function

Question 1

Describe the structure of the cell wall (in bacteria).

Answer 1

structure - composed of peptidoglycan in bacteria

peptidoglycan - contains many tetrapeptides

Question 2

glycan tetrapeptide

Answer 2

contains:

2 sugar derivatives

• n-acetylglucosamine (G)
• n-acetylmuamine (M)

a small umber of amino D and L enantimores

• are connected between amino form peptidoglycan

Question 3

Describe the cell wall structure of gram positive bacteria.

Answer 3

• thick layer of peptidoglycan

Question 4

Describe the cell wall structure of gram negative bacteria.

Answer 4

• thin layer of peptidoglycan
• multilayered and complex cell wall
• contains a second lipid bilayer, known as the outer membrane
• includes lipopolysaccharides (linked
  lipids and poly saccharides)
• it also contains a periplasm
  (perimplasimic space) between the
  cytoplasmic and outer membrane

Question 5

Describe the structure of the cytoplasmic membrane (bacteria).

Answer 5

• composed of a phospholipid bilayer
• some firmly embedded in the membrane
• integral membrane proteins
• also contains peripheral membrane proteins;
  not imbedded, associate with one of the
  membrane surfaces

Question 6

Describe the structure of the cytoplasmic membrane (archea).

Answer 6

1. membrane do not contain fatty acids; instead they have repeating units of isoprene
2. have eTHer (not ester) linkage between glycerol and the hydrophobic side chain

Some have lipid monolayers

• phytanyl molecules bonded together
• these are common in hyperthermophilic archaea
• more resistant to pealing apart at high temperatures

Question 7

What are the three main functions of the cytoplasmic membrane?

Answer 7

permeability barrier - prevents leakage and functions as a gateway for transport of nutrients into and out of the cell

protein anchor - site of many proteins involved in transport, bioenergetics, and chemotaxis

energy conservation - site of generation and use of the proton motive force

Question 8

What is the main function of the cell wall?

Answer 8

to provide the cell with structural strength

Question 9

simple transport

Answer 9

involves a membrane spanning protein

Question 10

group translocation

Answer 10

can involve a series of proteins and chemical modification

Question 11

ABC system (transporter)

Answer 11

• involves a substrate (or periplasmic binding protein)
• a membrane spanning protein
• and a ATP hydrolyzing protein

Question 12

How do gram negative and gram positive cells effect the gram stain?

Answer 12

In gram negative cells the insoluble crystal violet iodine complex is extracted
- cells can be counterstained pink

In gram positive cells the complex is not extracted because, of the thick peptidoglycan later
- cells remain purple

Question 13

cell illusions

Answer 13

function as important reserves

• carbon and energy storage granule
• glycogen
• poly-B-hydroxybulyrate
• phosphate granules
• accumulation of inorganic phosphate
• used for nucleic acid and phospholipid
  synthesis
• elemental sulfur granules
• reduces sulfur can be used for energy
  (chemolithotrophy)

Question 14

gas vesicles

Answer 14

associated with aquatic microorganisms

permit cells to change density to move u and down the water column

Question 15

endospores

Answer 15

are heat resistant, thick walled structures, produced by certain gram positive bacteria

• enables cells to remain dormant for a long period of time (many years)
• enables organisms to survive environmental extremes
• enables cells to disperse across different environments (dispersion)

Question 16

pili

Answer 16

• involved in attachment
• also involved in movement of plasmids between cells (conjugation)

conjugation - genetic exchange between plasmids

Question 17

fimbriae

Answer 17

• filamentous structures that extend from the cell surface

- involved in attachment