Multiple Choice
In the context of passive transport, how does oxygen (O2) typically cross the plasma membrane into a cell?
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9. Transport Across Membranes
Passive Transport: Diffusion and Osmosis
Multiple Choice
Which of the following best explains diffusion in the context of passive transport across cell membranes?
A
The movement of ions across a membrane against their electrochemical gradient using energy from ATP hydrolysis
B
The transport of specific molecules across a membrane via carrier proteins that bind solute and require ATP to change conformation
C
The movement of water across a selectively permeable membrane from lower solute concentration to higher solute concentration, driven by differences in water potential
D
The net movement of molecules from a region of higher concentration to a region of lower concentration due to random thermal motion
Verified step by step guidance1
Step 1: Understand the concept of diffusion as a type of passive transport, which means it does not require cellular energy (ATP) to occur.
Step 2: Recognize that diffusion involves the movement of molecules from an area of higher concentration to an area of lower concentration, driven by the random thermal motion of molecules.
Step 3: Differentiate diffusion from active transport, which requires energy and moves substances against their concentration or electrochemical gradients.
Step 4: Note that diffusion is a spontaneous process that aims to reach equilibrium, where the concentration of molecules is equal on both sides of the membrane.
Step 5: Conclude that the best explanation of diffusion in the context of passive transport is the net movement of molecules down their concentration gradient without the use of energy.
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