Topic 2-L3 - Bacterial Cytoplasmic Membranes

Question 1

Roles of the cell envelope

Answer 1

• Maintains barrier with environment
• Protects cell from stress
• Allows transport of nutrients into cell and waste out of cell
• Energy conservation/production
• And much more! Where much of the “action” takes place in a
  bacterium!

Question 2

Major structures of cell envelope can include:

Answer 2

Cytoplasmic membrane, cell wall,

outer membrane, S-layers

Question 3

All cells have a

Answer 3

cytoplasmic membrane (AKA “cell membrane”. In Gram negative bacteria, AKA “inner membrane”)

Question 4

Functions of the cytoplasmic membrane

Answer 4

1) permeability barrier
2) protein anchor
3) energy conservation

Question 5

transmembrane proteins

Answer 5

(are integral membrane proteins that pass all the way through membrane)
found throughout phospholipid bilayer

Question 6

one side of cytoplasmic membrane faces the cytoplasm

Answer 6

(cytoplasmic face)

Question 7

the other side of the shot plastic membrane faces outward

Answer 7

(periplasmic face).

Question 8

Two faces not identical.

Answer 8

E.g., many proteins embedded such that certain domains face one compartment or the other

Question 9

Cytoplasmic membrane: Proteins

Answer 9

• Proteins embedded in membranes
  (integral or transmembrane) have
  specific topologies.
• Inserted such that specific parts
  (ranging from short loops to large
  domains) face either cytoplasm or
  periplasm/cell wall.
• Amino acids that reside within the membrane typically hydrophobic
• Hydrophilic side chains often
  surface-exposed in cytoplasm or
  Periplasm