Multiple Choice
In passive transport, how does increasing a cell's surface area (while keeping the concentration gradient and diffusion distance constant) affect the rate of diffusion across its membrane?
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9. Transport Across Membranes
Passive Transport: Diffusion and Osmosis
Multiple Choice
In the context of passive transport, how is osmosis different from simple diffusion?
A
Osmosis moves solutes from low to high concentration using ATP, whereas simple diffusion moves water from high to low concentration without ATP.
B
Osmosis is the movement of any molecule down its concentration gradient, whereas simple diffusion is specifically the movement of water across a membrane.
C
Osmosis occurs only through transport proteins, whereas simple diffusion always requires vesicle-mediated transport (endocytosis).
D
Osmosis is the diffusion of water across a selectively permeable membrane, whereas simple diffusion is the net movement of solute molecules down their concentration gradient without requiring a membrane.
Verified step by step guidance1
Step 1: Understand the concept of simple diffusion. Simple diffusion is the passive movement of solute molecules from an area of higher concentration to an area of lower concentration, moving down their concentration gradient without the need for energy or a membrane.
Step 2: Understand the concept of osmosis. Osmosis is a specific type of passive transport that involves the movement of water molecules across a selectively permeable membrane from an area of lower solute concentration (higher water concentration) to an area of higher solute concentration (lower water concentration).
Step 3: Identify the key difference. Osmosis specifically refers to the movement of water, whereas simple diffusion refers to the movement of solute molecules.
Step 4: Note the role of the membrane. Osmosis requires a selectively permeable membrane that allows water to pass but restricts solutes, while simple diffusion can occur with or without a membrane depending on the context.
Step 5: Summarize the distinction. Osmosis is the diffusion of water across a selectively permeable membrane driven by solute concentration differences, whereas simple diffusion is the net movement of solute molecules down their concentration gradient without necessarily involving a membrane.
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