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