a. Movement of glucose and Na + through the apical
epithelial membrane in the intestinal epithelium
b. Movement of Na + and K + through the action of the
Na + /K + pumps
c. Movement of Na + and glucose across the kidney
tubules
d. Movement of Na + into a cell while Ca 2 + moves out
Als antwoord wordt b gegeven, maar volgens mij is d ook geen cotransport. In hetzelfde boek staat namelijk:
Dus in feite is optie d countertransport? Dus opties b en d zijn beide geen cotransport?
In secondary active transport, or coupled transport, the
energy needed for the “uphill” movement of a molecule or
ion is obtained from the “downhill” transport of Na + into the
cell. Hydrolysis of ATP by the action of the Na + /K + pumps is
required indirectly, in order to maintain low intracellular Na +
concentrations. The diffusion of Na + down its concentration
gradient into the cell can then power the movement of a different
ion or molecule against its concentration gradient. If the
other molecule or ion is moved in the same direction as Na +
(that is, into the cell), the coupled transport is called either
cotransport or symport. If the other molecule or ion is moved
in the opposite direction (out of the cell), the process is called
either countertransport or antiport.
(Human Physiology - S. Fox)
Wat denken jullie?
