Multiple Choice
In cell biology, what is diffusion?
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9. Transport Across Membranes
Passive Transport: Diffusion and Osmosis
Multiple Choice
Which statement best defines passive transport across a cell membrane?
A
Movement of substances down their concentration or electrochemical gradient without direct expenditure of cellular ATP
B
Directional movement of vesicles along microtubules using motor proteins to deliver membrane proteins to the plasma membrane
C
Movement of substances against their concentration gradient using energy from ATP hydrolysis
D
Bulk uptake of extracellular fluid and solutes into vesicles formed from the plasma membrane
Verified step by step guidance1
Step 1: Understand the concept of passive transport. Passive transport refers to the movement of molecules across a cell membrane without the use of cellular energy (ATP). It relies on the natural tendency of molecules to move from areas of higher concentration to areas of lower concentration, or down their electrochemical gradient.
Step 2: Identify key characteristics of passive transport: it does not require energy input, and substances move down their concentration or electrochemical gradient.
Step 3: Compare the given options to the definition of passive transport. Look for the option that mentions movement without ATP and down a gradient.
Step 4: Recognize that other options describe active transport (movement against gradient using ATP), vesicle transport (bulk uptake or motor protein-driven movement), which are not passive transport.
Step 5: Conclude that the correct statement defining passive transport is the one describing movement of substances down their concentration or electrochemical gradient without direct expenditure of cellular ATP.
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