MEMBRANE LIPID MOVEMENT
- Rotate
- Drift laterally
- Do NOT flip
MEMBRANE FLUIDITY DETERMINANTS
1. Lipid structure
- Degree of overlap
- Tail length
- Double bonds
2. Temperature
- Transition temperature (Tm) determined by membrane composition
- Membrane phase changes as physiologic temp. fluctuate about Tm
3.
Cholesterol
- Temperature buffer that resists changed in fluidity
MEMBRANE PHASES
1. Gel-like
- Little overlap of phospholipid tails
- Longer/saturated tails
- Higher Tm
- No cholesterol
2. Liquid ordered
- Physiologic temperature ~ membrane Tm
- Cholesterol present
- An intermediate phase and most common physiologically
3. Liquid disordered
- Tails overlap
- Shorter/unsaturated tails
- Lower Tm
- No cholesterol