1.3 MEMBRANE STRUCTURES

Question 1

Phospholipid bilayer

Answer 1

Phospholipids form bilayers in water due to the amphipathic properties of phospholipid molecules

Hydrophilic head- phosphate group attracted to water
Hydrophobic head- carbon tails not attracted to water
–> attracted to each other

= double membrane “bilayer”
Very stable structure

Question 2

Membrane proteins

Answer 2

Form barriers for ions and hydrophilic M
Hormone binding site
Cell adhesion 
Cell to cell communication 
Channels for passive transport- facilitated diffusion 
Pumps for active transport

Question 3

Cholesterol in membranes

Answer 3

Type of lipid 
Not far/oil = steroid 
Most in hydrophobic 
Attracted to tails 
Hydroxyl group on 1 end is hydrophilic 
Attracted to head 
30% of lipid is cholesterol

Question 4

Cholesterol
In membranes
FUNCTION

Answer 4

REDUCE FLUIDITY/ PERMEABILITY TO SOME SOLUTES
disrupts regular packing of tails
–> prevents crystallising/ solid
Restricts permeability to Na/ H IONS