Richard Crooks's Website
About Proteins
Proteins are, in my opinion, the most exciting molecules in biochemistry. They are the biological machinery that allows all the chemical reactions vital in life to take place.
The study of proteins is an enormously complex field, covering a vast amount of research. Different researchers are interested in specific proteins, classes of proteins, or particular properties found in many proteins.
Proteins encompass all sorts of molecules. There are structural proteins such as collagen and keratin that provide structure to tissues. There are enzymes that catalyze chemical reactions and allow them to take place quickly. There are motor proteins that move anything from structures within cells to whole joints. There are cell surface proteins that allow cells to respond to external stimuli. The range of proteins is vast.
Proteins are made up of long chains of amino acids. Amino acids are small molecules containing both an amino (-NH2) group and a carboxylic acid (-COOH) group. These groups are able to form peptide bonds between them, and as each amino acid contains one of each, they can extend their chains indefinitely.
Despite the variety in what proteins do, there are a few general concepts that underpin how all of them work. You can read more about them here.
Structure underpins what a protein does, and protein structures are organized in increasingly complex levels of structure. You can read about the different levels of structure here.
The primary sequence of a protein is the order that the amino acids are found in.
The secondary structure of a protein describes the short distance interactions between amino acids that are close to each other in the primary sequence.
The tertiary structure describes the longer distance interactions between amino acids further away that give the protein its gross shape.
The quaternary structure describes the interactions between the protein and other molecules, to give it its final functional form.
Proteins are held in their various structures by a wide variety of different forces, which allow the formation of structures which can be specific, or flexible. Different types of amino acids have a role in different types of interactions.
Because amino acids contain both carboxl and amine groups, they are able to ionize into molecules that have both positive and negatively charged parts of the same molecule. This makes them Zwitterions, which have interesting chemistry.