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Multiple Choice
Which of the following is an example of passive transport across a membrane?
A
Endocytosis of nutrients
B
Sodium-potassium pump activity
C
Exocytosis of waste products
D
Diffusion of oxygen molecules
Verified step by step guidance
1
Understand the concept of passive transport: Passive transport is the movement of molecules across a cell membrane without the use of energy by the cell. It relies on the concentration gradient, moving substances from an area of higher concentration to an area of lower concentration.
Identify the types of passive transport: The main types of passive transport include diffusion, osmosis, and facilitated diffusion. These processes do not require cellular energy (ATP).
Examine the given options: Analyze each option to determine if it involves passive transport. Endocytosis and exocytosis are active transport processes that require energy, as they involve the movement of large molecules or particles into or out of the cell.
Consider the sodium-potassium pump: This is an example of active transport, as it requires energy to move sodium and potassium ions against their concentration gradients.
Recognize diffusion of oxygen molecules: Diffusion is a type of passive transport where molecules move from an area of higher concentration to an area of lower concentration. Oxygen molecules naturally diffuse across cell membranes without the need for energy, making it an example of passive transport.