In fact, when looking at someone, you mostly see proteins since skin and hair are primarily made of them. Proteins acting as enzymes are particularly important substances because they trigger and control the chemical reactions by which carbohydrates, lipids, and other substances are created. When you look at another human being, you mostly see proteins. Our bodies produce about 90,000 thousand different kinds of proteins, all of which consist of simpler units called amino acids . Proteins in all organisms are mostly composed of just 20 kinds of amino acids.
Proteins differ in the number, sequence, and kinds of amino acids.
Our bodies produce some of these amino acids, while others come directly from food that we consume. T he largest molecules in people and other organisms are nucleic acids . Like proteins, they consist of very long chains of simpler units. However, the components, shapes, and functions of nucleic acids differ significantly from those of proteins. Both play critical roles in the production of proteins.