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Lipids in cellular membranes
Phospholipids, Glycosphingolipids, and cholesterol
Function of lipids in cellular membranes (3)
Glycosphingolipids: Cell recognition and signaling.
Cholesterol: Membrane fluidity and raft formation
Lipids of outer leaflet
(Phosphatidyl) choline, sphingomyelin, and glycosphingolipids
Lipids of inner leaflet
(Phosphotidyl) Serine, Ethanolamine, and inositol
Membrane fluidity
Lateral movement
Types of membrane fluidity (2)
Lateral diffusion
Flip-flop (Transverse diffusion)
Lateral diffusion
Rapid, within same leafelet
Flip-flop (Transverse diffusion)
Slow, one leafelet to another
Factors of Membrane fluidity
Ratio of saturated to unsaturated fatty acids and cholesterol content
Enzymes that assist with phospholipid translocation (3)
Flippases
Floppases
Scrablases
Flippases
Use ATP to move phosphatidylethanolamine and phosphatidylserine from the outer to the inner leaflet
Floppases
Use ATP to move phospholipids like phosphatidylcholine and sphingolipids from the inner to the outer leaflet.
Scrablases
Move phospholipids down their concentration gradient, disrupting membrane asymmetry and signaling apoptosis.
Saturated fatty acids effects on fluidity
packed tightly, decreasing membrane fluidity. At room temperature, they are solid.
Unsaturated fatty acids effects on fluidity
increase membrane fluidity due to their kinked structure, which prevents tight packing.
Cholesterol effect on fluidity
Makes saturated regions less fluid and unsaturated regions more fluid. It also broadens temperature range
Lipid rafts
Domains of sat. FA, cholesterol, and proteins. Help with signals, curvature, and interactions
Fluid Mosaic Model
Describes the membrane as a dynamic bilayer of amphipathic lipids with embedded proteins that can move laterally. It emphasizes fluidity, diversity, and functionality.