Multiple Choice
Transporter proteins transport solutes across the membrane via which of the following mechanisms?
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9. Transport Across Membranes
Principles of Transmembrane Transport
Multiple Choice
In the context of transmembrane transport, which statement correctly distinguishes active transport from passive transport?
A
Active transport occurs only through ion channels, whereas passive transport occurs only through carrier proteins (transporters).
B
Active transport moves solutes down their electrochemical gradient without energy input, whereas passive transport requires ATP hydrolysis to move solutes up their gradient.
C
Active transport occurs only in prokaryotic cells, whereas passive transport occurs only in eukaryotic cells.
D
Active transport requires an energy input (directly or indirectly, e.g., from ATP) to move solutes against their electrochemical gradient, whereas passive transport moves solutes down their electrochemical gradient without energy input.
Verified step by step guidance1
Step 1: Understand the definitions of active and passive transport. Active transport requires energy input to move solutes against their electrochemical gradient, while passive transport moves solutes down their electrochemical gradient without energy input.
Step 2: Recognize that active transport can use energy directly from ATP hydrolysis or indirectly through other energy sources, such as ion gradients, to move molecules against their concentration or electrochemical gradients.
Step 3: Note that passive transport does not require energy and relies on the natural movement of molecules from areas of higher concentration to lower concentration, often through channels or carrier proteins.
Step 4: Evaluate the given statements by comparing them to these definitions. For example, active transport is not limited to ion channels, nor is passive transport limited to carrier proteins; both can involve different types of membrane proteins.
Step 5: Conclude that the correct distinguishing statement is that active transport requires energy input to move solutes against their electrochemical gradient, whereas passive transport moves solutes down their electrochemical gradient without energy input.
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