Living organisms are composed of atoms, molecules, and macromolecules.

Atoms are the basic unit of matter and are composed of a nucleus surrounded by electrons.

Molecules are groups of atoms that are held together by chemical bonds and are the basic unit of compounds.

Macromolecules are large molecules that are composed of many smaller molecules. Macromolecules include proteins, carbohydrates, lipids, and nucleic acids.

Living organisms are composed of a variety of atoms, including hydrogen, carbon, nitrogen, oxygen, phosphorus, and sulfur. These atoms are organized into molecules, such as water, carbon dioxide, and glucose, which are essential for life. Macromolecules, such as proteins, lipids, and carbohydrates, are also essential for life and are responsible for many of the functions of living organisms.