Active and Passive Mechanisms

-- Passive Membrane Transport: diffusion - simple diffusion which is nonpolar and lipid-soluble substances, diffuse directly throughout the lipid bilayer, diffuse through channel proteins

-- Facilitated diffusion:
- transport of glucose, amino acids, and ions
- transported substances bind carrier proteins or pass through protein channels

-- Passive Membrane Transport: Osmosis:
- occurs when the concentration of a solvent is different on opposite sides of a membrane
- diffusion of water across a semipermeable membrane
- osmolarity - total concentration of soluble particles in a solution
- tonicity - how a solution affects cell volume

-- Passive Membrane Transport: Filtration:
- the passage of water and solutes through a membrane by hydrostatic pressure
- pressure gradient pushes solute-containing fluid from a higher-pressure area to a lower-pressure area

-- Active transport:
- Uses ATP to move solutes across a membrane.
- Requires carrier proteins.
- symport system: 2 substances are moved across a membrane in the same direction
- antiport system: 2 substances are moved across a membrane in opposite directions
- primary active transport: hydrolysis of ATP phosphorylates the transport protein causing conformational change
- secondary active transport: use of an exchange pump (such as the Na+ - K+ pump) indirectly to drive the transport of other solutes.