Membrane Structure

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Membrane Structure and Function
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The Plasma Membrane

• Is the boundary that separates the living cell
  from the non living surroundings
• Composed of lipids and proteins
• Bilayer
• Held together by hydrophobic interactions- less
  rigid than covalent bonds

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Fluid Mosaic Model

• Fluid
• Model of the membrane showing proteins bobbing in
  a fluid bilayer
• Lipids can move like fluid in a lateral motion (
  2D)
• Unsaturated hydrocarbon tails have kinks to keep
  from packing and enhance fluidity

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Fluid Mosaic Model

• Mosaic
• Collage of many different proteins embedded in
  the fluid matrix of the lipid bilayer
• The proteins determine the membrane function
• RBC have 50 different proteins on the Pl Mem.

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Plasma Membrane
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Whats in the membrane?

• Proteins
• Cholesterol
• Carbohydrates

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2 Main Proteins in the Membrane

• Integral protein
• Transmembrane protein with hydrophobic regions
  that span the hydrophobic interior of the
  membrane (nonpolar amino acids)

• Peripheral Protein
• Are not embedded in the lipid bilayer
• Appendages loosely bound to the surface of the
  membrane
• May be cytoplasmic or exterior

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Cholesterol

• Wedged between phospholipids
• Helps to stabilize membrane
• Due to warm temps of body it makes the membrane
  less fluid by restraining the movement of the
  phospholipid

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Carbohydrates on the Surface

• Glycoproteins- carb attached to protein
• Glycolipid- carb attached to lipid
• Serve as cell to cell recognition

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What do the proteins do?