Which of the following statements about diffusion is true?
A) It is very rapid over long distances
B) It requires an expenditure of energy by the cell.
C) It is a passive process in which molecules move from a region of higher concentration to a region of lower concentration
D) It is an active process in which molecules move from a region of lower concentration to a region of higher concentration.
The correct answer and explanation is :
The correct answer is C) Diffusion is a passive process in which molecules move from a region of higher concentration to a region of lower concentration.
Diffusion is a fundamental process where molecules move from an area of higher concentration to an area of lower concentration, driven by the concentration gradient, until equilibrium is reached. This movement is passive, meaning it does not require the cell to expend energy. The inherent kinetic energy of molecules causes them to move randomly, leading to diffusion.
To address the other options:
- A) It is very rapid over long distances: Diffusion is efficient over short distances, such as within a cell, but is not effective for long-distance transport. Over longer distances, diffusion becomes slow and inefficient.
- B) It requires an expenditure of energy by the cell: Diffusion is a passive process and does not require cellular energy (ATP). Molecules move down their concentration gradient without energy input.
- D) It is an active process in which molecules move from a region of lower concentration to a region of higher concentration: This describes active transport, not diffusion. Active transport requires energy to move molecules against their concentration gradient.
In summary, diffusion is a passive process where molecules move from high to low concentration areas without energy expenditure, making option C the correct choice.