Identifying Active Transport Mechanisms

Homeostasis is a fundamental concept in biology that describes the process by which living organisms regulate their internal environment to maintain stable, constant conditions despite changes in the external environment. One of the critical mechanisms for maintaining homeostasis is the transport of substances across cell membranes.

This transport process can be either passive or active. Passive transport occurs when substances move across cell membranes without the use of energy, often along the concentration gradient. Active transport, however, requires energy expenditure to move substances against their concentration gradient.

Which of the following describes a mechanism of transport that utilizes energy to move substances across a cell membrane, thereby contributing to homeostasis?