Cell Biology Unit Three

Cell Membrane Characteristics & Function Defines boundaries Serve as location for functions Facilitate and regulate movement of materials in & out of the cell Detect external signals Provides mechanisms for cell to cell communication

Cell Membrane Characteristics & Function

Cell Membrane Characteristics & Function

Cell Membrane Characteristics & Function In facilitating and regulating the movement of materials in & out of the cell, the membrane is said to be selectively permeable

Plasma Membrane Structure E face Phospholipid bilayer P face

Plasma Membrane Structure Membrane Protein Classes

Plasma Membrane Structure Glycoproteins

Plasma Membrane Structure

Membrane Transport

Passive Transport Does not require energy from the cell Substances move from an area of high concentration to an area of low concentration Substances can move in both directions, depending on the concentration gradient

Examples of Passive Transport Diffusion – the movement of a substance from an area of high concentration to an area of low concentration Facilitated diffusion – same as above, but with the help of membrane proteins Osmosis – the diffusion of water

Active Transport Does require energy from the cell Substances move from an area of low concentration to an area of high concentration Substances can move in only one direction, against the concentration gradient

Active Transport Example Sodium/Potassium pump – a membrane protein that moves sodium out, while moving potassium in

Active Transport

Bulk Transport Endocytosis * Phagocytosis * Pinocytosis

Bulk Transport Exocytosis

Osmosis Solute – substance that is dissolved in a medium (solvent) Solvent – substance (usually liquid) that dissolves a solute Solution – mixture of solutes dissolved in a solvent Osmotic pressure is created by the movement of water toward a higher solute concentration

Semipermeable membrane Osmosis Diffusion Semipermeable membrane Osmosis

Animal Cell Osmosis Crenated

Plant Cell Osmosis Turgor

Osmosis Edema – the excess collection of extracellular fluids due to high solute concentration Dehydration – the loss of extracellular fluids due to various causes