CAS BI 203 Lecture Notes - Lecture 95: Photosynthetic Reaction Centre, Peripheral Membrane Protein, Alpha Helix
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Document Summary
The plasma membrane-selective barrier that regulates the internal composition of the cell. Structure and composition of the plasma membrane. Hydrophobic fatty acid tails, hydrophilic head groups. All share the glycerol, fatty acid, phosphate, head groups change. Head groups are negatively charged- inner leaflet has a net negative charge. Two additional membranes lipids in animal cells: glycolipids (mostly outer leaflet), cholesterol (influences membrane fluidity) Sphingomyelin & cholesterol tend to cluster into semisolid patches- lipid rafts. Enriched in proteins involved in cell signaling and endocytosis. Note: the plasma membrane is not all lipid. About 50% lipid and 50% protein by weight. Proteins much larger than lipids, corresponds to about one protein per 50-100 molecules of lipid. Peripheral membrane proteins- interact w membrane by protein-protein interactions. Integral membrane proteins- portions are inserted into lipid bilayer- two mechanisms of insertion. Most are alpha helices of about 20-25 hydrophobic amino acids. Example structure #1: bacterial photosynthetic reaction center of r. viridis.