How is proteomics different from studying genes (genomics)?
The proteome of an organism is much larger and more complex than its genome. Many genes have the potential to produce more than one version of the protein they encode. In addition, proteins are frequently modified by cells after they are made. Protein modifications include the addition of various chemical groups, such as phosphate, acetate, and methyl groups, or the addition of carbohydrate (sugar) and lipid (fat) molecules. These modifications help regulate the function of proteins, as well as their location inside or outside of cells. Taking protein modifications into account, it has been estimated that the human body may produce more than 1,000,000 different protein species from its 20,000 to 25,000 protein-coding genes (7). This higher level of complexity is compounded by the fact that the protein composition of an organism or a tissue changes constantly as new proteins are made, existing proteins are eliminated, and proteins become modified or demodified in response to internal an
