The Plasma Membrane Cell Membrane The Fluid Mosaic
The Plasma Membrane (Cell Membrane) The Fluid Mosaic Model
Introduction WATCH THIS!!!
Functions 1. Separates the cell’s interior environment from the external environment. 2. Regulates what enters and exits the cell. 3. Communicates with other cells.
Selectively Permeable Based on size and solubility of molecule as well as specific protein channels.
Cell Membrane Structure • Phospholipid bilayer Isolation function • Proteins Regulation and Communication Functions • Glycoproteins (protein + carbohydrate) • Cholesterol molecules
The Phospholipid Bilayer • Phospholipids arranged as a continuous double layer.
The Fluid Mosaic Model Fluidity of Membrane • Phospholipids and proteins move laterally. • Components are not static. Mosaic-like • Composed of many different macromolecules.
The Fluid Mosaic Model
Components • Phospholipids – Bilayer acts as a barrier. – Hydrophobic nature causes membrane to be impermeable to watersoluble molecules. – Phospholipids are not bonded to one another, so this double layer is quite FLUID with the individual molecules moving about easily.
Components • Cholesterol – Structural support – prevents fatty acids from tangling – Regulates fluidity of membrane. • High temps: makes outer membrane less fluid. • Low temps: prevents the membrane from freezing and maintains membrane fluidity.
Components • Membrane Protein Classification 1. Integral • Embedded (integrated) in the phospholipid bilayer – – – Recognition proteins (special binding sites) Receptor proteins (receives signals) Transport proteins (channel or gated) • Can be attached to other proteins 2. Peripheral (smaller) • Bound to Integral Proteins or embedded in membrane (one side only), attached to cytoskeleton • Structural support
Components • Membrane Proteins
Components • Glycoproteins – Carbohydrate chains attached to membrane proteins. – On outer surface only.
Components • Glycolipids – Carbohydrate chains attached to the phospholipids. – On outer surface only.
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