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Cell Membrane

Cell Membrane. Variation of biomembranes in different cells. The faces of cellular membranes. Cytosolic face Exoplasmic face. Phospholipid bilayers

driscoll-york
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Cell Membrane

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  1. Cell Membrane

  2. Variation of biomembranes in different cells

  3. The faces of cellular membranes • Cytosolic face • Exoplasmic face

  4. Phospholipid bilayers • The phospholipid bilayer, the basic structural unit of allbiomembranes, is a two-dimensional lipid sheet with hydrophilicfaces and a hydrophobic core, which is impermeableto water-soluble molecules and ions.

  5. Properties: • Semi-permeable barrier • Stable structure maintained by van der Vaals and hydrophobic interaction.

  6. Lipid • Protein • Carbohydrate

  7. 磷酸甘油脂 • The primary lipid components of biomembranes are phosphoglycerides, sphingolipids, and steroids. glycerol

  8. sphingosine 鞘磷脂

  9. A phospholipid is a lipid that has a positively charged head that is linked by a phosphate group to the fatty acid tails. • A glycolipid has a head consisting of an oligosaccharide, linked to a fatty acid tail. • A sterol is a compound containing a planar steroid ring.

  10. General features of lipids

  11. Amphipathic structures have two surfaces, one hydrophilic and one hydrophobic. • Lipids are amphipathic. • Some protein regions may form amphipathic • helices, with one charged face and one • neutral face.

  12. Different cellular membranes vary in lipid composition .

  13. Phospholipids and sphingolipids are asymmetrically distributed in the two leaflets of the bilayer, whereas cholesterol is fairly evenly distributed in both leaflets.

  14. Asymmetry of lipids Phosphatidylserine (PS) only locates on the cytosolic face and glycolipids (oligosaccharide) on the exoplasmic face.

  15. Fluidity of Biomembrane • Most lipids and many proteins are laterally mobile in biomembranes.

  16. Fluorescence recovery after photobleaching (FRAP) experiments.

  17. Natural biomembranes generally have a fluidlike consistency. In general, membrane fluidity is decreased by sphingolipids and cholesterol and increased by phosphoglycerides.

  18. PM PC Placental alkaline phosphatase (yellow peaks) Lipid rafts

  19. Lipid rafts are microdomains containing cholesterol, sphingolipids, and certain membrane proteins that form in the plane of the bilayer. These aggregates are sites for signaling across the plasma membrane.

  20. Protein Composition • On the basis of the nature of the membrane–protein interactions. • Integral protein • Lipid-anchored protein • Peripheral protein

  21. Carbohydrates • O-link, Ser • N-link, Asp

  22. Common features of biomembrane • Selectively permeable, fluidity and asymmetry.

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