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CELL MEMBRANES

CELL MEMBRANES. Functions of the cell membrane. 1. Protection - barrier 2. Let in nutrients 3. Let out wastes/products 4. Receive messages from other cells. Phospholipids. Amphipathic nature of phospholipids: Hydrophilic head with Hydrophobic tails.

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CELL MEMBRANES

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  1. CELL MEMBRANES

  2. Functions of the cell membrane 1. Protection - barrier 2. Let in nutrients 3. Let out wastes/products 4. Receive messages from other cells

  3. Phospholipids • Amphipathic nature of phospholipids: Hydrophilic head with Hydrophobic tails. • Phospholipids could be made to arrange in a double layer in water, experimentally • Intracellular Fluid and Extracellular Fluid are both water-based  How would the phospholipids orient themselves?

  4. 1972: The Fluid Mosaic Modelof cell membrane • Fluid: Not rigid; flexible, and constantly moving. • Mosaic: Composed of many different components. Three major components: • Phospholipidbilayer • Cholesterol • Proteins

  5. phospholipids • Arranged in a bi-layer (tail to tail) • Phospholipids not bonded to one another. Held together by attraction/repulsion to water.

  6. cholesterol • Hydrophilic portion interacts with the phospholipid heads. • Hydrophobic portion embedded in the membrane. • Function: Alters (a)fluidity and (b)permeability. • Maintains the integrity of the cell membrane • Helps control substances going in and out of the cell.

  7. proteins • Two types: Integral and peripheral • Integral are embedded. • Peripheral are attached to the surface only.

  8. THE FLUID MOSAIC • The phospholipids are not rigidly bonded to one another. • The proteins and cholesterol are not fixed in their position, but are free to shift around within the phospholipidbilayer. • The fluid mosaic model is the prevailing model of cell membrane structure.

  9. Tomorrow: Getting things across cell membranes

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