Which passive process moves molecules from high to low concentration without energy input?

Which passive process moves molecules from high to low concentration without energy input?

• A. Biological Factor
• B. Disphotic Zone
• C. Diffusion
• D. Denitrifying Bacteria

Answer: (C)

Diffusion is the passive movement of molecules from an area of higher concentration to an area of lower concentration due to random thermal motion, requiring no energy input. In aquatic environments, this means solutes and gases spread through water or across membranes simply because molecules are constantly jostling and will gradually mix to balance concentrations. The rate depends on the size of the gradient, temperature (which increases molecular motion), surface area, and the size of the molecules involved. The other terms don’t describe a process where molecules move down a concentration gradient without energy input: one refers to a general factor affecting organisms, another to a depth zone in the ocean, and the last to bacteria that perform energy-requiring metabolism.

Diffusion is the passive movement of molecules from an area of higher concentration to an area of lower concentration due to random thermal motion, requiring no energy input. In aquatic environments, this means solutes and gases spread through water or across membranes simply because molecules are constantly jostling and will gradually mix to balance concentrations. The rate depends on the size of the gradient, temperature (which increases molecular motion), surface area, and the size of the molecules involved.

The other terms don’t describe a process where molecules move down a concentration gradient without energy input: one refers to a general factor affecting organisms, another to a depth zone in the ocean, and the last to bacteria that perform energy-requiring metabolism.