Active transport and cotransport Flashcards
what is active transport?
the use of energy to move ions/molecules across membranes, usually against a concentration gradient
What is the role of ATP in active transport?
ATP provides the energy needed, it undergoes ATP hydrolysis, forming ADP and Pi
How does an increase in the number of carrier proteins impact the rate of active transport?
more carrier proteins will increase the rate of active transport, as more molecules can be moved at the same time
Give three differences between active transport and facilitated diffusion
- Active transport requires energy, facilitated diffusion does not
- active transport moves from low concentration to high, facilitated diffusion moves from a high concentration to low
- Active transport only uses carrier proteins, facilitated diffusion used channel and carrier proteins
How do co-transport proteins transport molecules?
they bind to several molecules, one of which is moving down a concentration gradient, whilst the other is moving against the concentration gradient
Why would the rate of active transport eventually level off, even if the extracellular concentration of a solute increased?
As all the carrier proteins would be fully saturated
What carrier proteins are involved in the transport of glucose?
Na-K pump, transports Na+ ions into the blood (lowers conc. inside the cell)
Na-glucose, moves glucose against conc. gradient, as Na+ ions are moved down conc. gradient
How does active transport occur?
- specific carrier protein
- molecule binds externally
- ATP binds internally and is hydrolysed (Pi is bound, energy is released)
- leads to conformational change allowing movement of molecule
- Pi released, protein reverts to original shape and ATP is reformed
Why are Na+ ions actively transported into the blood in co-transport?
create sodium ion concentration gradient so that it will diffuse into cells from the ileum
How might cells be adapted to maximise rates of absorption?
large SA, lots of carrier proteins
