Membrane Protein : Integral/Peripheral Integral Membrane Proteins (transmembrane) – Exposed to aqueous environment on both sides of the membrane – Used to transport molecules across membrane Peripheral Membrane Proteins – Located on surface of a membrane – Eg. Cytoskeleton

Passive Membrane Transport No chemical energy required Diffusion – Net movement of a substance from a region of high concentration to a region of low concentration until dynamic equilibrium between cells is met

Simple Diffusion (Passive Transport) Diffusion of small/non-polar molecules across plasma membrane unassisted

Facilitated Diffusion Diffusion of large/polar molecules with the help of a transport protein (integral membrane protein) Stops when equilibrium is reached Two types of Transport (Integtral) Proteins – Channel proteins – Carrier proteins

Facilitated Diffusion Channel Proteins – Form hydrophilic pathways in the membrane – Water and certain ions can pass

Facilitated Diffusion Carrier Proteins – Form pathways through the membrane – Bind to a specific solute (glucose, amino acid) – Carrier protein changes shape allowing solute to move from one side of the membrane to the other

Osmosis Passive diffusion of water across a membrane via aquaporins Water always diffuses from an area of low solute concentration (high water concentration) to an area of greater solute concentration (low water concentration) Three Solutions (Cell) Hypotonic – Solute concentration is high in cell (swells) Hypertonic – Solute concentration is low in cell (shrinks) Isotonic – Solute and water concentration is equal both in and outside cell

Active Membrane Transport Substance carried across a membrane from an area of low concentration to an area of high concentration Use of pump ATP used as energy source

Exocytosis and Endocytosis Vesicles are used to transport ATP is required Exocytosis – Transport of proteins and waste material from cytosol to exterior of cell Endocytosis – Transport proteins and large molecules into cytosol of the cell.