Session 3.1: Primary and Secondary Active Transporters

Question 1

what is primary active transport

Answer 1

driven directly by hydolysis of ATP which is catalysed by the transporter itself

Question 2

what is an example of primary active transporter

Answer 2

plasma membrane Ca2+ ATPase (ca-mg-atpase)

hydrolysis of ATP used to drive calcium out of cell against concentration gradient

Question 3

what is an example of primary active transporter in reverse mode

Answer 3

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

Question 4

what are the different types of transporter

Answer 4

uniport, symport, antiport

Question 5

what is uniport

Answer 5

on its own, through a channel/transporter

Question 6

what is symport

Answer 6

2 ions/molecules in same direction (cotransport)

Question 7

what is antiport

Answer 7

2 ions/molecules in opposite direction (cotransport)

Question 8

how does the Na+-K+-ATPase pump work

Answer 8

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

Question 9

what are examples of alpha subunits

Answer 9

K+, Na+, ATP, ouabain binding sites

Question 10

what is the beta subunit and why is it so important

Answer 10

glycoprotein directs pumps to surface

allow transport of alpha subunit and association with pump

Question 11

why is Na+/K+/ATPase so important

Answer 11

establishes ion gradients that are used ins secondary active transport

Question 12

what is the purpose of the sodium pump in relation to membrane potential

Answer 12

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

Question 13

what is secondary active transport

Answer 13

driven indirectly by the energy released by hydrolysis of ATP to ADP
dissipation of gradient formed from another ion that provides energy

Question 14

what is an example of a secondary active transporter

Answer 14

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)

Question 15

which has a higher affinity for calcium

Answer 15

primary active transport

Question 16

what is another example of a secondary active transporter

Answer 16

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)

Question 17

what is another example of a secondary active transporter

Answer 17

Na+-glucose co transport
symport
sodium gradient drives inward movement of glucose against concentration gradient
eg: small intestine and kidney

Question 18

what happens with transporters in cystic fibrosis

Answer 18

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

Question 19

what happens with transporters in diarrhoea

Answer 19

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