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Multiple Choice
Which of the following describes a form of passive transport?
A
Diffusion of oxygen across a cell membrane
B
Endocytosis of large molecules
C
Movement of glucose via a symporter using ATP
D
Sodium-potassium pump activity
Verified step by step guidance
1
Step 1: Understand the concept of passive transport. Passive transport is the movement of molecules across a cell membrane without the use of energy (ATP). It relies on the concentration gradient, moving substances from areas of high concentration to areas of low concentration.
Step 2: Analyze the first option, 'Diffusion of oxygen across a cell membrane.' Diffusion is a classic example of passive transport, as oxygen moves from an area of high concentration (outside the cell) to an area of low concentration (inside the cell) without requiring energy.
Step 3: Evaluate the second option, 'Endocytosis of large molecules.' Endocytosis is an active transport process that requires energy to engulf large molecules into the cell, so it does not qualify as passive transport.
Step 4: Examine the third option, 'Movement of glucose via a symporter using ATP.' The use of ATP indicates active transport, as energy is required to move glucose against its concentration gradient, making this option incorrect for passive transport.
Step 5: Assess the fourth option, 'Sodium-potassium pump activity.' The sodium-potassium pump is an active transport mechanism that uses ATP to move sodium and potassium ions against their concentration gradients, so it is not a form of passive transport.