Multiple Choice
Which of the following statements is correct regarding net diffusion across a membrane?
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9. Transport Across Membranes
Passive Transport: Diffusion and Osmosis
Multiple Choice
In the context of passive transport (diffusion and osmosis), which process requires no energy input (ATP) from the cell?
A
Simple diffusion of oxygen across the phospholipid bilayer
B
Endocytosis of extracellular fluid by pinocytosis
C
Exocytosis of neurotransmitters from synaptic vesicles
D
Primary active transport of and by the sodium-potassium pump
Verified step by step guidance1
Identify the key concept: Passive transport involves the movement of molecules across the cell membrane without the use of cellular energy (ATP). This includes processes like simple diffusion and osmosis.
Understand simple diffusion: It is the movement of small, nonpolar molecules (like oxygen) directly through the phospholipid bilayer from an area of higher concentration to an area of lower concentration, requiring no energy input.
Recognize other processes listed: Endocytosis, exocytosis, and primary active transport all require energy because they involve moving substances against their concentration gradients or engulfing materials into vesicles.
Compare each option to the definition of passive transport: Only simple diffusion fits the criteria of no energy usage and movement down a concentration gradient.
Conclude that simple diffusion of oxygen across the phospholipid bilayer is the process that requires no ATP, distinguishing it from energy-dependent processes like endocytosis, exocytosis, and active transport.
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