Which term denotes the process of moving substances across a membrane with energy, often against a gradient?

Which term denotes the process of moving substances across a membrane with energy, often against a gradient?

• A. Adaptation
• B. Active Transport
• C. Artificial System of Classification
• D. Autotroph

Answer: (B)

Active transport is the process where a cell uses energy to move substances across a membrane against their concentration gradient. Energy, usually from ATP, powers membrane pump proteins that change shape to shuttle ions or molecules from low to high concentration. This energy requirement sets it apart from passive processes like diffusion or facilitated diffusion, which let substances move down their gradients without direct energy input. Some active transport uses the energy stored in an existing gradient to move another solute, but the key idea remains: movement with energy against a gradient. Other terms here don’t describe this mechanism—adaptation is a trait that helps survival, autotroph refers to an organism that makes its own food, and an artificial system of classification is unrelated.

Active transport is the process where a cell uses energy to move substances across a membrane against their concentration gradient. Energy, usually from ATP, powers membrane pump proteins that change shape to shuttle ions or molecules from low to high concentration. This energy requirement sets it apart from passive processes like diffusion or facilitated diffusion, which let substances move down their gradients without direct energy input. Some active transport uses the energy stored in an existing gradient to move another solute, but the key idea remains: movement with energy against a gradient. Other terms here don’t describe this mechanism—adaptation is a trait that helps survival, autotroph refers to an organism that makes its own food, and an artificial system of classification is unrelated.