What type of transport process describes molecules moving from high to low concentration?

The transport process that describes molecules moving from an area of high concentration to an area of low concentration is diffusion. This passive transport mechanism relies on the natural kinetic energy of molecules, allowing them to move freely across a gradient until equilibrium is reached.

In diffusion, there are no energy requirements since it occurs without the input of cellular energy. This process can involve gases or solutes and is vital for many physiological functions, such as the exchange of oxygen and carbon dioxide in the lungs, as well as the movement of nutrients and waste products across cell membranes.

While osmosis specifically refers to the movement of water molecules through a selectively permeable membrane and involves a similar concentration gradient, it is a distinct process with specific relevance to water transport. Facilitated diffusion, on the other hand, involves specific transport proteins to help move substances across cell membranes but still follows the concentration gradient. Active transport is different, as it requires energy to move molecules against their concentration gradient, from low to high concentration. Hence, diffusion is the correct answer to describe the movement from high to low concentration.