Something all macromolecules have in common is some degree of repeating structure. Artificial polymers, such as plastics tend to be very homogenous, meaning that they are composed of identical repeating units. Some natural polymers, particularly polysaccharides are also homogenous in nature. Starch and cellulose, for example, are both polysaccharides formed by the repeated linkage of glucose molecules. The structures of the other natural polymers vary considerably. Proteins and nucleic acids are comprised of repeating units having different groups; it is these differences that give both types of molecules their specific properties.
Artificial macromolecules, usually referred to as polymers or plastics, are synthesized using a process called polymerization. The starting materials of polymers are called monomers, which can be made to react with themselves any number of times to form stable, long-chained molecules. Polymerization often also requires a catalyst or initiator to facilitate this conjugation. Polymerization catalysts provide "work space" in which polymers can grow, and they usually are organic molecules with metallic cores.
Deoxyribonucleic acid (DNA) is found in the nucleus of every plant and animal cell. The structure of DNA dictates all of the characteristics that are inherited in offspring from their parents. Some creatures, such as bacteria, reproduce without mating, meaning that new bacteria are genetically identical to their parents. In high lifeforms, such as mammals, DNA is donated from both parents at the point of conception. DNA exists as an intertwined double helix which unravels to allow duplication. During cell division, information from DNA is copied onto another type of nucleic acid called ribonucleic acid (RNA) which is then used by the cell to build a new DNA molecule for a new cell.
DNA also provides a blueprint for the synthesis of proteins in animal and plant cells. Nucleic acids have a backbone of ribose or deoxyribose molecules. Ribose are linked together by phosphate molecules to form a very long chain. Variation in nucleic acids is due to compounds called bases that are attached to the ribose. DNA features four types of compounds called bases: adenine, cytosine, guanine and thymine. It is these four bases that form the code of DNA.
Proteins are synthesized in cells using information from certain sections of DNA molecules. As with cell division, this information is transferred via RNA, which is read by a special type cell molecule called a ribosome. A ribosome acts a both a translator and an assembly plant, using the information in the RNA to build a specific protein. How ribosomes translate information from mRNA to create proteins is incredibly complex and not yet fully understood.