According to the University of New Mexico, macromolecules are large molecules that are created by the polymerization of smaller molecules. Nucleic acids, proteins, lipids and carbohydrates are the four classes of macromolecules.
Macromolecules are made of smaller molecules. In carbohydrates and proteins these smaller particles are referred to as monomers. When two similar or identical monomers are bonded together they form a larger polymer molecule. The monomers of carbohydrates are monosaccharides or simple sugars, and when two or more of these are linked by a covalent bond it creates a disaccharide. When they are bonded together they form a complex sugar or a polysaccharide. The monomers of proteins are called amino acids, which can be strung together in different combinations known as polypeptide chains.
Carbohydrates are the first macromolecules that are used as energy for the body. They are often referred to as fast fuel. Glucose and cellulose are both examples of carbohydrates. Lipids are stored inside the body as reserve energy because they are harder to break down than carbohydrates, but they do contain more energy per unit than carbohydrates. Once the body uses all of the fast fuel it has, it begins breaking down lipids which are stored in the body as fat molecules, including triglycerides.