What term describes the movement of substances through a semi-permeable membrane from a low to a high concentration?

The movement of substances through a semi-permeable membrane from a low to a high concentration is best described as active transport. This process requires energy to move molecules against their concentration gradient, which is why it is distinct from passive processes like diffusion and osmosis.

In osmosis, the movement specifically pertains to water molecules across a semi-permeable membrane and occurs from an area of low solute concentration (high water concentration) to an area of high solute concentration (low water concentration) without the input of energy.

In contrast, active transport involves the use of energy (usually from ATP) to move ions or molecules through a membrane where they are less concentrated to an area where they are more concentrated, resulting in an increase of the concentration gradient. This mechanism is crucial for maintaining proper cellular functions and homeostasis in living organisms.

Understanding the difference between these processes is essential in plant and animal physiology, as well as in various agricultural practices where nutrient uptake is vital.