The cell contains organelles that carry out specific functions. The two major parts are the nucleus, which contains the cell's DNA, and the cytoplasm. Protoplasm makes up the cell and is composed of water, electrolytes, proteins, lipids, and carbohydrates. Water acts as a solvent, electrolytes provide inorganic chemicals, proteins serve structural and enzymatic roles, lipids provide energy storage and cell signaling, and carbohydrates provide nutrition. Cell membranes surround and separate organelles and delimit the cell.