Organic compounds function in all living things as carbohydrates, lipids, protein and nucleic acids. All these components provide the energy and the means to maintain and create life.
Carbohydrates provide energy for all living things and form the basis for some of their structures. Simple carbohydrates, or sugars, are monosaccharides that are directly absorbed. Glucose is a monosaccharide that is the basic fuel for life. Cellular respiration begins with glucose, and is the main product of photosynthesis.
Linked monosaccharides, or polysaccharides, are complex carbohydrates that are broken down by enzymes into simple sugars so they can be absorbed by the body. Most important are the starches, which are a storage form for carbohydrates. Glycogen is stored in the liver as glucose. Cellulose, such as cotton fabric and paper, is primarily a structural carbohydrate.
Lipids make up waxes, fats and the steroids that compose many hormones. When oxidized, fat provides almost twice the energy of carbohydrates. Fats are often stored in plant seeds and in the adipose tissue of animals for reserve energy.
All life consists of proteins, which build and repair tissues and make up the enzymes that catalyze chemical reactions inside cells. Proteins also store a cell’s reserve energy.
There are two types of nucleic acids: deoxyribonucleic acid and ribonucleic acid. DNA stores and transfers genetic information, while RNA directly codes for amino acids and serves as the messenger between DNA and ribosomes to make proteins.