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Anatomy and Physiology
Cells
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Chapter 3
Cell Structure and Function
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Cell Characteristics
• Plasma Membrane– Outer cell boundary
• Cytoplasm – Cytosol– Cytoskeleton– Cytoplasmic inclusions
• Organelles– Specialized structures that perform specific
functions
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Functions of the Cell
• Basic unit of life• Protection and support• Movement• Communication• Cell metabolism and energy release• Inheritance
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Plasma Membrane
• Intracellular versus extracellular• Membrane potential• Glycolipids and glycoproteins• Fluid-mosaic model
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Membrane Lipids
• Phospholipids form a lipid bilayer– Hydrophilic (water-loving) polar heads– Hydrophobic (water-fearing) nonpolar heads
• Cholesterol: Determines fluid nature of membrane
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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
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Marker Molecules
• Allow cells to identify on another or other molecules
• Glycoproteins• Glycolipids• Examples:
– Immune system– Recognition of oocyte
by sperm cell
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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
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Receptors
• Receptor molecules– Exposed receptor site
• Linked to channel proteins– Acetylcholine
• Linked to G proteins– Alter activity on inner
surface of plasma membrane
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Enzymes and Carrier Proteins
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Movement through the Plasma Membrane
• Diffusion• Osmosis• Filtration• Mediated transport mechanisms
– Facilitated diffusion– Active transport– Secondary active transport