Answer the following question given this paragraph: 

Inside every cell of all living things, energy is needed to carry out life processes. Energy is required to break down and build up molecules and to transport molecules across plasma membranes. All life’s work needs energy. A lot of energy is also simply lost to the environment as heat. The story of life is a story of energy flow—its capture, its change of form, its use for work, and its loss as heat. Energy, unlike matter, cannot be recycled, so organisms require a constant input of energy. Life runs on chemical energy. Where do living organisms get this chemical energy?.


Q: What is required to break down and build up molecules and to transport molecules across plasma membranes?

 Choices:

- salt

- electricity

- calcium

- energy

A:
energy
