Multiple Choice
In cell biology, diffusion is an example of which type of transport across membranes?
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9. Transport Across Membranes
Passive Transport: Diffusion and Osmosis
Multiple Choice
Which of the following is an example of passive transport across a cell membrane?
A
Large particles being engulfed by the plasma membrane during phagocytosis
B
Oxygen diffusing from an area of higher concentration to lower concentration across the lipid bilayer
C
Glucose entering a cell via a symporter that uses the sodium gradient (secondary active transport)
D
Sodium ions moving into a cell through the Na+/K+ ATPase pump using ATP
Verified step by step guidance1
Step 1: Understand the definition of passive transport. Passive transport is the movement of molecules across a cell membrane without the use of cellular energy (ATP), typically moving down their concentration gradient.
Step 2: Analyze each option to determine if it requires energy or moves molecules against their concentration gradient. For example, phagocytosis involves engulfing large particles and requires energy, so it is not passive transport.
Step 3: Recognize that oxygen diffusing from an area of higher concentration to lower concentration across the lipid bilayer fits the criteria of passive transport because it moves down its concentration gradient without energy input.
Step 4: Identify that glucose entering via a symporter using the sodium gradient is a form of secondary active transport, which indirectly uses energy, so it is not passive transport.
Step 5: Note that sodium ions moving through the Na+/K+ ATPase pump use ATP directly, making this an example of active transport, not passive transport.
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