Membrane structure Flashcards
What are biological membranes composed largely of?
Biological membranes are composed largely of lipids and proteins
Structure of a phospholipid
Amphiphatic
-Hydrophilic head
-Hydrophobic tail
In what fashion do lipids form a bilayer?
Lipids spontaneously form bilayers in aqueous solutions
Where does phospholipid synthesis take place?
Phospholipid synthesis takes place on the cytosolic surface of the endoplasmic reticulum
How are membrane lipids synthesised and processed in bilayer?
- Newly synthesised phospholipids
- One side enlarges compared to the other
- Transfer of newly synthesised phospholipid to the luminal side
What does floppase do and what does it require?
moves phospholipids from the inner to the outer leaflet
-Requires ATP
What does Flippase do?
moves phospholipids from the outer to the inner leaflet
-Requires ATP
What does scramblase do?
bidirectional movement
How is the lateral movement like of lipids?
Lateral movement of lipids in the
membrane is rapid
How is transverse movement like of lipids?
Transverse movement is slow and
requires the action of three enzymes
What factors alter membrane fluidity?
- Temperature
- Fatty acid composition
- Chain length
- Degree and extent of
saturation - Cholesterol content
What happens phospholipid bilayer with cholesterol as temperature increases?
-At low temperatures, fluidity increased
-At high temperatures, fluidity decreased
What is spur cell anaemia and what does this do to membrane fluidity?
Cholesterol content increased by 25-65%
leading to decreased membrane fluidity
what are integral membrane proteins?
Transmembrane domain often an a-
helix
What type of bonds hold the integral membrane proteins?
Strong non-covalent
bonds
