Proteins are large, complex molecules that perform the vast majority of tasks required for life, acting as everything from biological scaffolds to tiny machines. They are among the most abundant organic molecules in living systems. Proteins possess the most diverse range of functions among all biological macromolecules. Because of their immense variety, a single alternate name is insufficient, leading to multiple classifications based on their chemistry and role in the body.
Structural Names for Proteins
The most direct chemical alternate name for a protein is the term polypeptide. Proteins are polymers, meaning they are long chains built from smaller, repeating units called amino acid residues. These units are linked together by strong chemical bonds known as peptide bonds, forming the protein’s primary structure. The term polypeptide specifically refers to this linear chain of amino acid residues.
However, the terms polypeptide and protein are not entirely interchangeable. A polypeptide is technically an unfolded string of amino acids, typically containing more than 20 units. Proteins are generally much larger, often containing over 50 amino acids, and may consist of multiple polypeptide subunits.
The crucial distinction lies in the three-dimensional structure and function. A functional protein is a polypeptide chain that has twisted and folded into a highly specific, stable shape. This precise folding determines the protein’s activity. While all proteins are polypeptides, not all polypeptides have folded correctly to become functional proteins.
Functional Names for Proteins
Many common alternate names for proteins are classifications that describe the specific biological job the molecule performs. Proteins are grouped into functional categories, giving them titles that reflect their role rather than their chemical structure.
The following are key functional names used for proteins:
- Enzymes act as catalysts for biochemical reactions, accelerating processes like digestion by factors of a million or more without being consumed.
- Hormones are messenger proteins, such as insulin, that transmit signals and coordinate processes between different tissues and organs.
- Structural proteins provide physical scaffolding, exemplified by collagen in connective tissues or keratin in hair and nails.
- Antibodies or immunoglobulins are defense proteins that specifically bind to foreign particles like viruses and bacteria to protect the body.
The Fundamental Building Blocks
All proteins are built from fundamental units called amino acids, which are the monomers that link together to form the long polypeptide chains. There are 20 standard types of amino acids used in the creation of proteins across all forms of life. The side chain, or R group, of each amino acid is unique. The specific sequence of these building blocks dictates the final three-dimensional structure and function of the resulting protein.
The human body can synthesize some of these internally, known as non-essential amino acids. However, nine specific amino acids cannot be produced by the body in sufficient quantities. These nine are designated as essential amino acids and must be acquired through diet to support the body’s continuous need to build and repair proteins.