Macromolecules are very large molecules that are composed of a number of atoms and smaller molecular structures. There are a number of different types of macromolecules, many of which are very useful or important to life. Plastics, rubber, and diamond are all formed from macromolecules. Four classes of macromolecules, the biopolymer macromolecules, are fundamentally important to living things and biology as a whole.
Proteins, like all macromolecules, are composed of smaller units that combine and connect together to form one larger molecule. Amino acids, which are smaller, simpler molecules, connect end to end to form proteins. Because there are 20 different amino acids that all life uses and requires, there are a number of possible combinations, and thus, a large number of possible proteins. Each protein has its own particular function, ranging from attacking antigens in the blood, to regulating metabolism, to digesting particles of food. Proteins are involved in most life processes.
DNA and RNA are nucleic acids, macromolecules that contain and describe the genetic code. Nucleic acids serve as a detailed instruction manual for the development of the body and the workings of each cell. Nucleic acids are built with the sugar 2-deoxyribose, a phosphate group, and one of four base molecules. Different combinations of the four base molecules along the DNA chain encode for certain amino acids, which eventually connect together to form proteins. While DNA contains the raw genetic information for life, RNA passes messages between DNA and the cell.
Carbohydrates are macromolecules found in many foods that provide energy for the muscles, the central nervous system, and the body in general. Carbohydrates are polymers of water and carbon, and contain nothing but carbon, hydrogen, and oxygen. The body breaks down carbohydrates into their base components, which are then used to fuel cells and maintain body processes. Plants use carbohydrates, particularly cellulose, to protect their cells and to grow larger. There are many kinds of carbohydrates, including all sugars and starches.
While carbohydrates supply immediate energy for the body, lipids are a class of macromolecule that provide long-term energy storage. Lipids are more commonly known as fats, and appear in many foods. There are dozens of lipids, many of which are important for living things. Lipids form the protective membranes around cells and deliver essential vitamins, among other functions. Lipids are stored by the body as reserves of fat, but the reserves will be depleted over time as cells use the stored energy.