What is cell made of?

Cells are made of water (approximately 70% of cell mass), proteins, lipids (fats), nucleic acids (DNA and RNA), carbohydrates, and inorganic ions, all organized into complex structures called organelles that perform specialized functions within the cell.

Water provides the medium where chemical reactions occur and helps maintain cell structure and temperature. It dissolves and transports nutrients, eliminates waste, and facilitates molecular interactions. Proteins represent the most diverse cellular molecules, comprising approximately 15-20% of cell mass. They function as enzymes (catalyzing chemical reactions), structural components (cytoskeleton maintaining cell shape), transporters (moving molecules across membranes), signaling molecules (hormones, receptors), and immune defenders (antibodies). Lipids (fats), constituting about 5-10% of cell mass, form cell membranes (phospholipid bilayers creating boundaries between cell interior and exterior, and between organelles), store energy (triglycerides in fat cells), and function as signaling molecules (steroid hormones). Nucleic acids—DNA (deoxyribonucleic acid) storing genetic information and RNA (ribonucleic acid) implementing genetic instructions—together comprise about 2-3% of cell mass. Carbohydrates provide energy (glucose), short-term energy storage (glycogen), structural support (in plant cell walls), and cell recognition markers (on cell surface). Inorganic ions including sodium, potassium, calcium, chloride, and others regulate electrical charges, enzyme activity, and cellular signaling, though they represent less than 1% of mass. These molecules organize into organelles: the nucleus containing DNA, mitochondria producing energy, endoplasmic reticulum synthesizing proteins and lipids, Golgi apparatus processing proteins, lysosomes breaking down waste, and others. The cell membrane encloses everything, regulating what enters and exits. Understanding cellular composition informs medicine—targeting specific cellular molecules enables precise therapies, while nutritional requirements reflect cells' need for building blocks (amino acids from proteins, fatty acids from fats, sugars from carbohydrates) to construct and maintain these components.