Multiple Choice
In the context of principles of transmembrane transport, which statement best describes a key difference between simple diffusion and facilitated diffusion across a plasma membrane?
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9. Transport Across Membranes
Principles of Transmembrane Transport
Multiple Choice
In the context of principles of transmembrane transport, how is facilitated diffusion similar to simple diffusion?
A
Both can transport solutes against their concentration gradient as long as a membrane protein is present.
B
Both exhibit saturation kinetics in which transport rate plateaus at high solute concentration.
C
Both require a specific membrane transport protein that binds the solute and undergoes a conformational change each transport cycle.
D
Both move solutes down their concentration (electrochemical) gradient and do not require direct ATP hydrolysis.
Verified step by step guidance1
Step 1: Understand the basic concept of simple diffusion, which is the passive movement of solutes from an area of higher concentration to an area of lower concentration without the need for energy or membrane proteins.
Step 2: Recognize that facilitated diffusion also moves solutes down their concentration gradient, but it requires specific membrane transport proteins to help solutes cross the membrane.
Step 3: Note that both simple diffusion and facilitated diffusion do not require direct ATP hydrolysis, meaning they are passive transport processes relying on the natural movement of molecules down their electrochemical gradient.
Step 4: Differentiate facilitated diffusion from active transport by understanding that active transport moves solutes against their concentration gradient and requires energy, whereas both simple and facilitated diffusion do not.
Step 5: Conclude that the similarity between facilitated diffusion and simple diffusion lies in their direction of solute movement (down the concentration gradient) and their independence from direct energy input (ATP hydrolysis).
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