Multiple Choice
Which of the following is an example of active transmembrane transport (requires energy input to move a solute against its electrochemical gradient)?
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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
Glucose moving into a cell through a GLUT transporter down its concentration gradient
B
Oxygen diffusing directly through the lipid bilayer from high to low concentration
C
Na+/K+ ATPase pumping Na+ out of the cell and K+ into the cell using ATP hydrolysis
D
Water moving across the plasma membrane through aquaporins in response to an osmotic gradient
Verified step by step guidance1
Step 1: Understand the difference between passive and active transport. Passive transport moves substances down their concentration or electrochemical gradients without energy input, while active transport requires energy to move substances against these gradients.
Step 2: Identify the examples given and classify them based on whether they require energy and the direction of solute movement relative to gradients.
Step 3: Recognize that glucose moving through a GLUT transporter and oxygen diffusing through the membrane are passive processes because they move down their concentration gradients without energy.
Step 4: Note that water moving through aquaporins is also passive, driven by osmotic gradients, and does not require energy.
Step 5: Conclude that the Na+/K+ ATPase example is active transport because it uses ATP hydrolysis to pump Na+ and K+ ions against their electrochemical gradients, requiring energy input.
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