Which of the following is a key function of cells?

• A. Carry out metabolic processes.
• B. Carry out photosynthesis.
• C. All cells require no energy.
• D. Coordinate long-distance signaling.

Answer: (A)

All living cells rely on metabolic processes—the chemical reactions that break down nutrients to release energy and to build the molecules a cell needs for growth, repair, and division. This turnover of energy and materials powers every other function a cell performs, making metabolism a universal and defining activity of cells.

Photosynthesis happens only in certain cells that have the machinery to capture light and fix carbon; many cells do not have this capability, so it isn’t a universal function of cells. The idea that all cells require no energy is false because cells must constantly use energy to drive active transport, synthesize biomolecules, and carry out movements. Coordinating long-distance signaling is an organism-level process involving tissues and hormones, not something every cell is responsible for, even though some cells do participate in signaling.