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Unformatted text preview: Chapter 3 Cell Structure and Function Cell Characteristics Plasma Membrane Outer cell boundary Cytoplasm Cytosol Cytoskeleton Cytoplasmic inclusions Organelles Specialized structures that perform specific functions Functions of the Cell Basic unit of life Protection and support Movement Communication Cell metabolism and energy release Inheritance Plasma Membrane Flexible but sturdy barrier that surround cytoplasm of cell Fluid mosaic model describes its structure sea of lipids in which proteins float like icebergs membrane is 50 % lipid & 50 % protein held together by hydrogen bonds lipid is barrier to entry or exit of polar substances proteins are gatekeepers -- regulate traffic 50 lipid molecules for each protein molecule Lipid Bilayer of the Cell Membrane Phospholipids form a lipid bilayer Hydrophilic (water-loving) polar heads Hydrophobic (water-fearing) nonpolar heads Cholesterol: Determines fluid nature of membrane Membrane Proteins Integral or intrinsic Extend from one surface to the other Peripheral or extrinsic Attached to either the inner or outer surfaces of the lipid bilayer Membrane Proteins Marker Molecules Allow cells to identify on another or other molecules Glycoproteins Glycolipids Examples: Immune system Recognition of oocyte by sperm cell Channel Proteins Nongated ion channels Always open Ligand gated ion channel Open in response to small molecules that bind to proteins or glycoproteins Voltage-gated ion channel Open when there is a change in charge across the plasma membrane Receptors Receptor molecules Exposed receptor site Linked to channel proteins Acetylcholine Linked to G proteins Alter activity on inner surface of plasma membrane Enzymes and Carrier Proteins Movement through the Plasma Membrane Diffusion Osmosis Filtration Mediated transport mechanisms Facilitated diffusion Active transport Secondary active transport Diffusion Movement of solutes from an area of higher concentration to lower concentration in solution Concentration or density gradient Difference between two points Viscosity How easily a liquid flows...
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