Membrane Trafficking Notes

Biomembranes are lipid bilayers, mainly of phosphoglycerides & sphingolipids,created by the amphiphilic nature of lipid molecules. How does this structure dictate membrane function, and what implications do alterations in lipid composition have for cellular processes?

Cholesterol regulates membrane fluidity, increasing fluidity and rigidity. How does cholesterol's structure enable it to modulate membrane fluidity, and how might changes in cholesterol levels affect membrane-dependent processes?

Phospholipids spontaneously form micelles and lipid bilayers. What factors drive the self-assembly of phospholipids into these structures, and how might cells exploit this property?

Lipid bilayers are 2D fluids with fast lateral diffusion. How do short, unsaturated lipids and saturated lipids affect $T*m$ , and what implications does this have for membrane function at different temperatures?

Liquid-disordered (ld) phase: Lipids have full freedom of motion. Liquid-ordered (lo) phase: Lipids diffuse freely but maintain ordered acyl chains, facilitated by cholesterol. How do those phases coexist and how does this coexistence impact membrane organization and function?

Lateral phase separation involves the coexistence of ld and lo liquid phases. How do variations in composition of Phophatidylcholin, Spingomyelin and Cholesterol affect phase separation in liposomes, and what implications might this have for membrane organization in cells?

Rafts are small, dynamic regions involved in membrane traffic, cell signaling, immune response, and apoptosis. What experimental evidence supports the existence of lipid rafts, and how do they contribute to cellular processes?

Enriched in Spingomyelin and Cholesterol, inducing the lo phase, affect protein distribution based on lipidation. How does the lipid composition of rafts influence protein sorting and activity, and what are the functional consequences?

Lipid rafts can form detergent-resistant membranes when treated with detergents like Triton X-100. What insights do DRMs provide into membrane organization, and what are the limitations of using detergents to study lipid rafts?

Lipid composition differs between monolayers. Example: Red blood cells have phosphatidylcholine and sphingomyelin on the outer layer, while phosphatidylserine is on the inner layer. Negatively charged phosphatidylserine on the inner layer recruits proteins like protein kinase C (PKC) or Srk. Phosphatidylserine on the outer layer induces phagocytosis, signaling apoptosis. Glycolipids are exclusively on the monolayer facing outside of the cytosol. How does this asymmetry contribute to cellular functions such as signaling and apoptosis?