How is energy best defined in a biological context?

In a biological context, energy is best defined as the ability to do work. In living organisms, energy is essential for various biological processes, including metabolism, movement, growth, and reproduction. When cells perform work, they convert energy stored in chemical bonds (from nutrients) into forms that can be used to drive cellular processes, such as synthesizing molecules, transporting substances across membranes, and facilitating muscle contraction.

The concept of energy in biology often ties back to thermodynamics, where energy is not just a static entity but actively involved in transforming physical and chemical states to achieve cellular functions and maintain life. This definition aligns well with the role of ATP (adenosine triphosphate) in cells, which provides the necessary energy for reactions and activities that sustain life, thereby underscoring the significance of energy as the capacity to do work in biological systems.