Organic compounds are those that contain carbon. These compounds, such as glucose, triacylglycerol, and guanine, are used in day-to-day metabolic processes. Many of these molecules are polymers formed from repeated smaller units called monomers.
Inorganic compounds are those that do not contain carbon. These make up a very small fraction of mass in living organisms and are usually minerals such as potassium, sodium, and iron.
There are several classes of organic compounds commonly found in living organisms. These biological molecules include carbohydrates, proteins, lipids, and nucleic acids, which, when combined, make up more than 95 percent of non-water material in living organisms.
Carbohydrates (sugars) are molecules made of carbon, hydrogen, and oxygen. Sugars are primarily used in organisms as a source of energy: they can be catabolized (broken down) to create energy molecules such as adenosine triphosphate (ATP) or nicotinamide adenine dinucleotide (NAD+).
The monomer of carbohydrates is the monosaccharide, a sugar with the formula CnH2nOn. Glucose, for example, is the monosaccharide C6H12O6.
Structure of Glucose
Simple sugars like glucose can bond together to form polymers called polysaccharides. Some polymers of glucose include starch, which is used to store excess sugar, and cellulose, which is a support fiber responsible in part for the strength of plants.