Question
Which is the transport system shown below?
| A. |
GLUT 4 |
| B. |
Sodium glucose symporter |
| C. |
P Glycoprotein |
| D. |
Na⁺-K⁺ ATPase pump |
|
Correct Answer � C Explanation |
 |
Image Interpretation:
– Shows active transport needing ATP hydrolysis.
– Depicts export (efflux) of substance out of cell.
– Uses ATP → ADP + Pi, consistent with primary active transport.
– Common in drug efflux mechanisms.
P-glycoprotein:
– P-glycoprotein (MDR1) is an ATP-dependent efflux pump.
– Pumps drugs/toxins out against concentration gradient.
– Key in drug resistance in cancer, blood-brain barrier, intestines, kidneys, liver.
Why Other Options Are Incorrect:
A. GLUT4:
– Facilitated glucose diffusion into muscle/adipose, insulin-dependent.
– Does not use ATP, is passive, not an efflux pump.
B. Sodium-glucose symporter (SGLT):
– Secondary active transport using Na⁺ gradient, not ATP directly.
– Imports glucose into cells, no efflux.
D. Na⁺/K⁺-ATPase pump:
– Primary active transport using ATP, exchanges Na⁺ out/K⁺ in.
– Ion pump, not specific for drugs/toxins or drug efflux.