What is diffusion?

What is diffusion?

• A. Active transport requiring energy
• B. Movement of particles from high to low concentration due to random motion
• C. Movement of water across a semipermeable membrane
• D. Chemical bonding between molecules

Answer: (B)

Diffusion is the passive spread of particles from regions of higher concentration to regions of lower concentration, driven by their random thermal motion. This means molecules move and mix on their own until the concentrations are even, without the cell needing to supply energy. That’s why diffusion is described as a process that doesn't require external energy input. In contrast, active transport uses cellular energy to move substances, so it’s not diffusion. Osmosis is a specific type of diffusion focusing on the movement of water across a semipermeable membrane, but the general idea of diffusion covers the spread of many types of particles, not just water. Chemical bonding between molecules is about how atoms connect, not about how substances move from one area to another. So the statement that best captures diffusion is the movement of particles from high to low concentration due to random motion.

Diffusion is the passive spread of particles from regions of higher concentration to regions of lower concentration, driven by their random thermal motion. This means molecules move and mix on their own until the concentrations are even, without the cell needing to supply energy. That’s why diffusion is described as a process that doesn't require external energy input.

In contrast, active transport uses cellular energy to move substances, so it’s not diffusion. Osmosis is a specific type of diffusion focusing on the movement of water across a semipermeable membrane, but the general idea of diffusion covers the spread of many types of particles, not just water. Chemical bonding between molecules is about how atoms connect, not about how substances move from one area to another.

So the statement that best captures diffusion is the movement of particles from high to low concentration due to random motion.