module 2 - 5.4 active transport Flashcards
what does diffusion lead to?
equilibrium of concentrations
how do you maintain a concentration gradient?
molecules must be moved UP the conc. gradient at a rate faster than they diffuse DOWN the conc. gradient
what is active transport?
movement of molecules or ions across a cell membrane from lower to higher conc. AGAINST/ UP conc. gradient
is active transport selective or non selective?
selective - specific shape of pore
what does ‘pump’ mean?
that what’s happening is always an active process
what happens if substrate molecules are moving from lower to higher concentration? (active transport)
- specific transmembrane proteins are required
- these proteins have receptor sites that bind to specific molecules and transport them across cell membrane
- energy for this supplied by ATP
where does active transport often take place?
internal lining of small intestine
which proteins does active transport use?
carrier proteins
what do plants need to absorb from the soil, and where do these things exist?
- absorbs mineral salts
- only exist in very dilute solutions in soil water
what does active transport enable for the cells in the plant?
enables them to take up salts from dilute solution against direction of conc. gradient
what is the possible mechanism for active transport?
- molecule binds to receptor site on inner wall of the pore on the carrier protein
- ATP cytoplasm side of carrier protein, then hydrolysed into ADP +Pi, energy is transferred, and Pi is bound, to carrier protein
- carrier protein changes shape to open the pore to other side of membrane, molecule is released to inside of cell
- Pi released from carrier protein, carrier protein changes shape again do adopt original shape
what are the two types of bulk transport?
- endocytosis
- exocytosis
what is endocytosis?
substances moving from out of the cell to in
what processes does endocytosis involve?
- phagocytosis
- pinocytosis
- receptor-mediated endocytosis
what does phagocytosis form?
phagosome (vacuole)
