19 Membrane Transport Flashcards
the relative ion concentrations of the cell relative to the inside and the outside of the cell
The inside of the cell is relatively negative, compared to the outside of the cell which is positively charged.
passive transport
diffusion of molecules in a net movement from high to low concentration, no energy applied
active transport
net movement from a region of low concentration to a region of high concentration, uses energy to move substances against their gradient
uniport
transport of one compound across the membrane
symport
simultaneous transport of two molecules across the membrane in the same direction
antiport
exhange of two molecules acros the membrane in opposite directions
aquaporins
water can move through these aquaporins, large protein pores, either in or out of the cell depending on its concentration gradient, water flows from an area of high concentration to an area of low concentration
simple diffusion
movement of gases and lipid soluble molecules down their concentration gradient from high to low concentration, no energy required
facilitated diffusion
transport mediated by protein transporters or carrier proteins, usually involves a conformational change, net mov’t down its concentration gradient and thus, no energy is required.
gated channels
channels form a pore for ions that is opened or closed in response to stimuli
Transporter proteins in facilitated diffusion
the transported molecule binds to a specific carrier protein, conformational change takes place and then release of molecule on the other side. high specificity
primary active transport
the energy is applied directly to the transport protein, example Na+/K+ ATPase, to move molecules against its concentration gradient
secondary active transport
the energy is applied more indirectly, by the establishment of a concentration gradient, and this drives the movement of another compound
GLUT type glucose transporters
Moves glucose from a high concentration to a low concentration, either into or out of the cell, passive transporter, moves the glucose down its gradient
Na+/K+ ATPase (antiport)
primary active transport , it pumps 3 Na+ ions out of the cell and 2 K+ ions are driven inside the cell, they are both against their concentration gradient ,
ATP supplies the
ENERGY to cause the conformational change to releases the bound Na+ ions to the other side of the membrane (antiport)
Na+ glucose cotransporters (symport)
2 active transport, symport. Na+ gradient established, the Na+ moves down its concentration gradient to move the glucose against its gradient, 1:1 transport across the membrane together.
ABC transporters (CFTR)
a ligand gated channel controlled by phosphorylation.
- Protein kinase A phosphorylates this regulatory binding domain, causes a conformational change which allows ATP to bind to the 2 ABD binding domains.
- Hydrolysis of the ATP drives the opening of the channel
contains two regulatory binding domains which controls the opening of the channel
Ca2+ ATPase examples (pmca and serca)
both channels work to lower Ca2+ concentration inside the cell, by pumping it out through the PM or into the sarcoplasmic reticulum
SERCA, active transport, uniport, located in the SR, Moves Ca2+ into the SR, and then ATP is needed to release Ca2+ into the lumen of the SR,
PMCA, active transport, uniport, located at the PM, pumps Ca2+ against its gradient from the cytosol, through PM and into the extracellular space
Na+-Ca2+ exchanger (antiport)
secondary active transport, antiport example NCX
pumps 3 Na+ into cell down its gradient while pumping 1 Ca2+ out of cell against its gradient
cell membrane transporter
