Cell transport Flashcards
Diffusion vs active transport
Diffusion: movement of a molecule across the cell membrane from high concentration to low concentrations - does not require energy.
Active: movement of molecule against the concentration gradient require energy
Simple vs facilitated diffusion
Simple: does not require attachment with a carrier protein.
Depends on: amount of substance present, kinetic energy of molecule, number and size of opening available in the membrane
Facilitated: requires carrier protein. Molecule or ion binds with carrier protein and conformation change occurs and transported across the membrane.
Voltage gated vs ligand gated
Voltage gated channels: Gate opens or closes in response to voltage (action potential) difference across the membrane. Eg: When ICF becomes negative then outer gate is closed for Na and it transports across when ICF starts getting less negative leading to open the channel.
Ligand gated: Gate opens or closes after binding of a ligand and causes membrane conformation change or chemical bonding change permitting transport. eg: ACH binding to ACH receptor
Primary active vs secondary active transport
Primary: energy required for transport is derived directly from the ATP.
Secondary: energy derived from the concentration difference of molecules or ions across the membrane created by primary transport
Different trasport mechanism with examples
simple diffusion: transport of lipid and other lipid soluble substance Eg: steroid, CO2, O2
Facilitated diffusion:
1. ion channels: diffusion of water through Aquaporins
2. carrier protein: ligand binding to proteins channel
Primary active: Na-K ATPase pump, transport of Ca (in cardiac cells) and H (in stomach and renal tubules)
Secondary transport:
Co-transport (symporter): Na and glucose transport - in the same direction (SGLT2 - in renal epithelial cellsand intestine epithelial cells)
counter transport (antiporter): Na and Ca or Na and H - in opposite direction
