What molecules are carbon atoms in before the chemical change?

Before a chemical change, carbon atoms can be found in a variety of molecules, including organic compounds like carbohydrates, lipids, proteins, and nucleic acids, as well as inorganic compounds such as carbon dioxide (CO2) and carbonates (e.g., calcium carbonate). In these molecules, carbon typically forms covalent bonds with other atoms, contributing to the diverse structures and functions of organic and inorganic substances. The specific molecules present depend on the context and the chemical environment.