There are three levels of structure in the formation of a protein: the primary, secondary, and tertiary structures (wow, how obvious). Let us examine these.
The primary structure is simply the sequence of amino acids, as directed by the genetic information found in the nucleus. Pretty simple enough.
The secondary structure is formed by the hydrogen bonds that are formed between the amino acids. There are two kinds of hydrogen bonding between amino acids, and therefore two kinds of secondary structure.
When the hydrogen bonds are intrachain, meaning they are within the same polypeptide chain, they form a helical structure called the alpha-helix. On the other hand, interchain hydrogen bonding (H-bonding among two different polypeptide chains) produce a stable structure called a pleated sheet (or a beta sheet).
The tertiary structure refers to the overall shape of the protein: either long and narrow, or globular. The tertiary structure is determined by many different kinds of interactions, such as hydrogen bonding, dipole-dipole interactions, ionic bonds, covalent bonds, and London dispersion forces.
An important amino acid that contributes to the tertiary structure is cysteine that forms a disulfide linkage in the presence of an oxidizing agent:
Protein structure may be damaged by too much heat, radiation, and pH changes. This is called denaturation. For example, when we hard boil an egg, we have denatured the proteins that make up the egg.
Proteins
- Amino acids
- Protein structure
- Enzymes