Multiple Choice
In the context of principles of transmembrane transport, which molecule is directly used as an energy source for primary active transport across the plasma membrane?
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9. Transport Across Membranes
Principles of Transmembrane Transport
Multiple Choice
In the context of principles of transmembrane transport, what does active transport require to move a solute across a membrane against its electrochemical gradient?
A
No membrane protein; solute crosses freely through the lipid bilayer regardless of polarity
B
An input of energy, such as ATP hydrolysis or coupling to an ion gradient
C
Only an open aqueous channel (pore) that permits passive diffusion
D
Movement of solute down its concentration gradient without energy input
Verified step by step guidance1
Understand that active transport is the movement of solutes across a membrane against their electrochemical gradient, which means moving from a region of lower concentration to higher concentration or against an electrical potential difference.
Recognize that moving solutes against their gradient is energetically unfavorable and cannot occur spontaneously without an energy input.
Identify that active transport requires a specific membrane protein, such as a pump or transporter, that can use energy to change its conformation and move the solute across the membrane.
Know that the energy input for active transport often comes from ATP hydrolysis, which provides the necessary free energy to drive the transport process.
Alternatively, active transport can be coupled to the movement of another ion down its gradient (secondary active transport), using the energy stored in that gradient to move the solute against its own gradient.
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