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Plasma Membrane (Chap. 5) Structure

Plasma Membrane (Chap. 5) Structure. http://home.earthlink.net/~shalpine/anim/Life/memb.htm. Thickness of 7-8nm Primarily made up of phospholipids (Fig. 5.2 in text) Have different types of proteins and cholesterol dispersed between the phospholipids.

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Plasma Membrane (Chap. 5) Structure

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  1. Plasma Membrane (Chap. 5) Structure http://home.earthlink.net/~shalpine/anim/Life/memb.htm

  2. Thickness of 7-8nm • Primarily made up of phospholipids (Fig. 5.2 in text) • Have different types of proteins and cholesterol dispersed between the phospholipids. • The fluid mosaic model – membrane can move and yet is very stable because of hydrophobic and hydrophilic properties of phospholipids • Proteins are visible by a freeze-fracture technique where tissue is frozen (use liquid N2) and then split along the phospholipid bilayer through its hydrophobic tails. Viewed by SEM or TEM.

  3. The Plasma Membrane; Three Main Components (other than phospholipids) 1. Cholesterol • amphipathic (have both hydrophilic and hydrophobic regions just like phospholipids) • prevents the fatty acid tails from packaging tightly therefore, membrane is more fluid-like. • however at the same time, it decreases permeability to small water-soluble molecules. (Understand Fig. 5.8 in text)

  4. 2. Proteins • Functions • hormone binding sites • some are enzymes that carry out reactions right in the membrane • electron carriers (more on this later) • channels for passive and active transport of materials in and out of the cell

  5. Categories of Proteins I. Integral proteins • amphipathic • some go through only one of the phospholipid layers of the membrane (lipid-anchored proteins) and others extend completely through the membrane and are well secured (transmembranal proteins) II. Peripheral proteins • lie on the surfaces of the membrane • usually attached to the protruding portions of integral membrane proteins

  6. 3. Glycocalyx • visible (by TEM) as a fuzzy, outermost region of the cell. • a sugar coating over the membrane surface made up of short chains of glucose attached to the proteins (glycoprotein) and/or phospholipids (glycolipid) • helps: • protect the cell • the cell recognize, identify, and interact with other chemicals, viruses, and bacteria

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