Which of the following statements about passive transport is correct?

• A. Passive transport operates independently of diffusion.
• B. Passive transport operates independently of the concentrations of the moving solute.
• C. In passive transport, solute movement stops when the solute concentration is the same on both sides of the membrane.
• D. Passive transport does not occur in the human body.
• E. Passive transport permits the solute to move in either direction, but the net movement of solute molecules occurs down the concentration gradient of the molecule.

Answer: (E)

Verified step by step guidance

1. Understand the concept of passive transport: Passive transport is a type of cellular transport where substances move across cell membranes without the need for energy input from the cell. It relies on the natural motion of particles and the concentration gradient.
2. Identify the role of diffusion in passive transport: Diffusion is a key mechanism in passive transport. It involves the movement of molecules from an area of higher concentration to an area of lower concentration until equilibrium is reached.
3. Analyze the statement about solute concentration: In passive transport, solute movement continues until the concentration of the solute is equal on both sides of the membrane, achieving equilibrium. This is a fundamental characteristic of diffusion.
4. Consider the occurrence of passive transport in the human body: Passive transport is a common process in the human body, facilitating the movement of substances like oxygen, carbon dioxide, and small ions across cell membranes.
5. Evaluate the correct statement: The correct statement about passive transport is that it allows solute molecules to move in either direction, but the net movement is down the concentration gradient. This means that while individual molecules can move in both directions, the overall movement is from high to low concentration.