Sugar molecules are also used as starting material for molecules like the amino acids and nucleotides from which larger more complicated molecules used by our bodies are formed. In the picture above, the little black lines between atoms represent the chemical bonds which you can think of as sort of like hand holding between the atoms. It's how they hold on to each other. It's not really how they look. Carbohydrate molecules have twice as many hydrogen atoms as carbon and oxygen.
Carbon atoms have a quirk.
This ability to hold on to four other atoms, allows for a tremendous diversity and variety of molecules based on the carbon atom attached to other atoms. Pretty much all living things are built around carbon based molecules. The study of the chemistry and molecules of living things is basically the study of the chemistry of carbon. Living compounds are based on carbon atoms attaching to themselves and to other atoms. Back to the Top of the Page Oxygen is not just used by our bodies for respiration .