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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