M&R Session 1- The Membrane Bilayer Flashcards
0
Q
What is the dry weight membrane composition?
A
60% protein
40% lipid
1-10% carbohydrate
(20% water as membranes are hydrated structures)
1
Q
What are the five functions of biological membranes?
A
- continuous, highly selective permeable barrier
- control a chemical environment
- communication- between cells and their environment
- recognition- signalling molecules, adhesion proteins and immune surveillance
- signal generation- in response to a stimulus.
2
Q
What is the composition of a phospholipid?
A
Glycerol, 2 fatty acid side chains, a phosphate head group
3
Q
How do fatty acids increase phospholipid membrane fluidity?
A
Unsaturated fatty acids contain a cis double bond which produce a kink. This reduces tightness of phospholipid packing and therefore increases membrane fluidity.
4
Q
What does amphipathic mean?
A
Both hydrophobic and hydrophilic moieties
5
Q
What four mobilities do membrane lipids have?
A
- flip-flop
- lateral diffusion within the bilayer
- flexion (vibration)
- axial rotation
6
Q
What is the role of cholesterol within a membrane?
A
To stabilise it!
7
Q
How does cholesterol perform its function?
A
- reduces membrane fluidity by binding to the carbonyl group of phospholipids and therefore reducing chain motion.
- increases membrane fluidity by binding to this carbonyl group and consequently decreasing tightness of packing of phospholipids.
