Proteins

Functions

The functions of proteins are structured, functional, and being a food source. Proteins make up all of the structures in living things. For example, actin and myosin are muscle proteins. Keratin makes up horns, nails, feathers, and hair. The bones, teeth, blood vessels, and ligaments in your body are made up of collagen. Proteins are made up of an amino group, a carboxyl group, and a side chain (an r group) 

The amino acids in proteins bind together with peptide bonds and involves dehydration synthesis (because one water is lost). Two amino acids is a dipeptide. This grows to become a tripeptide (3 amino acids). In the end, a polypeptide is formed, which can have anywhere between 30 and 30,000 amino acids. Proteins differ because of the order of their amino acids. There are four levels of protein structure: 

1. Primary Structure

Primary structure is the first level in the forming of proteins. The amino acids are simply joined together with peptide bonds. This sequence if amino acids will determine the characteristics of the protein. 

2. Secondary Structure

This is the second step in forming a protein. An alpha helix (also called a beta pleated sheet) is formed because of the negative carboxyl group being attracted to the positive amino group. This results in the formation of hydrogen bonds.

 

 

 

3. Tertiary Structure

Some R groups will react with other R groups in the chain. These are either amino acids that are charged or that have a sulphur atom. When the positive/negative attrations and the sulphur bridges interact, the molecule is folded into a very specific 3D shape. This shape is what determines the protein's job in the body.

 

 



4. Quaternary Structure

This is the final stage in protein formulation, and is does not apply to all proteins. The proteins that reach this stage are actually two or more molecules joined together with ionic bonds. Examples are insulin (2 subunits) and hemoglobin (4 subunits).