The differences in concentration or electrical potential across a membrane are referred to as what?

The correct choice, which indicates the differences in concentration or electrical potential across a membrane, is gradients. In biological systems, gradients are essential for processes such as diffusion and osmosis. They represent the change in concentration of solutes across a membrane, leading to the movement of substances from areas of higher concentration to areas of lower concentration, or vice versa, depending on the specific context.

Additionally, gradients can refer to electrical potential differences that exist across biological membranes, which are crucial for the functioning of cells, particularly in the context of nerve impulses and muscle contractions. The membrane potential created by these gradients is vital for cellular activities and communication.

Filters, transporters, and compounds describe other aspects of biological systems but do not specifically refer to the differences in concentration or electrical potential across a membrane. Filters generally pertain to mechanisms that separate substances, transporters refer to proteins that facilitate the movement of substances across membranes, and compounds are chemical substances formed from two or more elements.