Session 3.1: Primary and Secondary Active Transporters Flashcards
what is primary active transport
driven directly by hydolysis of ATP which is catalysed by the transporter itself
what is an example of primary active transporter
plasma membrane Ca2+ ATPase (ca-mg-atpase)
hydrolysis of ATP used to drive calcium out of cell against concentration gradient
what is an example of primary active transporter in reverse mode
F1/F0 ATPase (ATP sythetase)
in inner membrane of mitochondria
uses proton gradient to allow reentry of protons into matrix through ATPsynthase to form ATP
what are the different types of transporter
uniport, symport, antiport
what is uniport
on its own, through a channel/transporter
what is symport
2 ions/molecules in same direction (cotransport)
what is antiport
2 ions/molecules in opposite direction (cotransport)
how does the Na+-K+-ATPase pump work
uses hydrolysis of ATP, to pump 3 Na out and 2 K in against gradient
a type of antiport - primary active transporter
called a P-type ATPase - ATP phosphorylates - confrimational change for transport of ions
what are examples of alpha subunits
K+, Na+, ATP, ouabain binding sites
what is the beta subunit and why is it so important
glycoprotein directs pumps to surface
allow transport of alpha subunit and association with pump
why is Na+/K+/ATPase so important
establishes ion gradients that are used ins secondary active transport
what is the purpose of the sodium pump in relation to membrane potential
creates a gradient for potassium. this high concentration of potassium in the intracellular space, and it is the K+ diffusion that is mainly responsible for membrane potential (-70mV), wheras sodium pump does little to affect membrane potential
what is secondary active transport
driven indirectly by the energy released by hydrolysis of ATP to ADP
dissipation of gradient formed from another ion that provides energy
what is an example of a secondary active transporter
Na+-Ca2+ exchanger
sodium gradient is driven by primary active transporter
uses the gradient allow re entry of sodium along electrochemical gradient to provide energy for removal of calcium out of the cell (antiport)
which has a higher affinity for calcium
primary active transport
what is another example of a secondary active transporter
Na-H exchanger
uses sodium gradietn from primary transport
this energy used to drive hydrogen ions out of the cell(involved in regulation of pH)
what is another example of a secondary active transporter
Na+-glucose co transport
symport
sodium gradient drives inward movement of glucose against concentration gradient
eg: small intestine and kidney
what happens with transporters in cystic fibrosis
sodium potassium ATPase and Na/cl/k
in epithelial cells - chloride into cell and potassium out of cell. the chloride transferred across membrane into lumen of alveoli through a cystic fibrosis transmembrane conductance regulator (CFTR). water follows the chloride (for constituency of mucus.) this CFTR can mutate, then chloride can not pass, so water no longer follows, mucus surfaces becomes thick
what happens with transporters in diarrhoea
sodium potassium ATPase and Na/Cl/K
when infected, activates protein kinase A, which phosphorylates CFTR and increases its activity. chloride more readily passed, as is water - cholera
