Multiple Choice
Which of the following is a form of active transmembrane transport?
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9. Transport Across Membranes
Principles of Transmembrane Transport
Multiple Choice
Which of the following is an example of active transmembrane transport (requires energy input to move a solute against its electrochemical gradient)?
A
Water movement through aquaporins down an osmotic gradient
B
Na+ uptake by the Na+/K+ ATPase
C
Glucose movement into a cell via GLUT1 (facilitated diffusion)
D
Oxygen diffusion directly through the lipid bilayer
Verified step by step guidance1
Step 1: Understand the difference between passive and active transport. Passive transport moves molecules down their concentration or electrochemical gradient without energy input, while active transport requires energy to move molecules against their gradient.
Step 2: Analyze each option to determine if energy input is required and if the movement is against the electrochemical gradient.
Step 3: Water movement through aquaporins occurs by osmosis, which is passive transport because it follows the osmotic gradient and does not require energy.
Step 4: Glucose movement via GLUT1 is facilitated diffusion, a type of passive transport where glucose moves down its concentration gradient without energy input.
Step 5: Na+ uptake by the Na+/K+ ATPase involves ATP hydrolysis to pump Na+ against its electrochemical gradient, making it an example of active transmembrane transport.
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