Question

question 5 the energy used by cells comes from - molecules diffusing across the cell membrane. the synthesis of water molecules. proteins produced in the ribosomes. the breakdown of food and oxygen.

Explanation:

Cells obtain energy mainly through cellular respiration, which is the breakdown of food (usually glucose) in the presence of oxygen. Protein synthesis in ribosomes is not an energy - producing process for the cell but an energy - consuming one. Water synthesis is not a major energy - yielding process. Diffusion of molecules across the cell membrane is a passive process that does not produce energy for the cell.

Answer:

the breakdown of food and oxygen.