Glucose provides energy to the cell. The mitochondria in our cells break down glucose into useable energy in the form of ATP and ADP. This energy is transmitted to various cells in the body for brain and body functioning. Protein works in muscle cells to maintain the shape and strength of the cell. Proteins also serve as communicators between cells. Certain protein structures trigger organ cells to start performing activities such as digestion or skin regeneration. In addition, proteins trigger developmental genetic processes in human embryonic cells. Lipids help a cell maintain its shape. The cell membrane and cell wall are made of lipid layers.