All carbon-containing substances, often known as organic chemicals, found in living organisms are classified as biomolecules. They are organic substances found in living cells that play a role in living organisms’ management and metabolic processes. Organic molecules such as carbohydrates, protein, nucleic acid, and lipids make up the cell and cellular organelles. A biomolecule is a good name for them. A cell also contains inorganic components like water and minerals.

Proteins have been identified as the “building blocks of life” because they are the most plentiful substances in the body, accounting for roughly 60% of cell dry weight. They are by far the most prominent type in all living things. The word “protein” comes from the Greek word “proteios,” which means “first or foremost.” The proteins are polymers of α-L-amino acids.

Structure of proteins: 

Proteins are made up of a polymeric chain of amino acids. A protein’s structure is primarily made up of polypeptide chains. Proteins have specific features according to the structure and location of amino acids. An amino-functional group (-NH2) and a carboxyl group make up amino acids (-COOH).

Common Amino Acid

A peptide bond or peptide linkage joins the polymers of a-amino acids that make up common amino acid proteins. Peptide linkage is chemically defined as an amide produced by the -COOH group and the -NH2 group.

Classification of the protein:

1. Fibrous proteins: A fibre-like structure is generated when polypeptide chains run parallel and are kept together by hydrogen and disulphide bonds. In most cases, these proteins are water-insoluble. Keratin is a good example.
2. Globular proteins: When polypeptide chains coil around each other to form a spherical shape, this structure is formed. These are frequently water-soluble. Globular proteins include insulin and albumin, for example.
3. Protein structure and shape can be investigated at four levels: primary, secondary, tertiary, and quaternary, with each level being much more complicated than the last:
4. Primary structure of proteins: One or more polypeptide chains can be found in a protein. Each polypeptide is a protein made up of amino acids linked together in a particular manner, which is referred to as the protein’s primary structure.
5. Secondary structure of proteins: A protein’s secondary structure describes the shape that a lengthy polypeptide chain can take. They can be characterized by two sorts of structures: α-helix and β-pleated sheet. Hydrogen bonding between a ketone and the –NH- groups of the peptide bond leads the core of the polypeptide chain to fold in a periodic rhythm.
6. The tertiary structure of proteins: The final 3-dimensional shape obtained by polypeptide chains under the electrostatic repulsion of the distinct R-groups of each amino acid is known as the tertiary structure. This is a coiled shape that is extremely important for protein activity.
7. Quaternary structure of proteins: Only proteins that have many polypeptide chains combining to form a big structure. Subunits are the names given to the individual chains.

Functions of Protein:

Proteins have a variety of activities in the body, and their structure determines how they work.

1. Digestion: Digestion is accomplished by digestive enzymes, which are primarily proteinaceous in origin.
2. Cellular communication: Cells use receptors on their surfaces to establish cell to cell communication and the outside world. Proteins make up these receptors.
3. Keratin is the structural protein that gives our hair, nails, and animal their support and structure.
4. Movement: Myosin is a protein present in muscles that allow muscles to contract, allowing for mobility.
   Perform as a messenger:
5. These proteins produce chemicals, messengers, allowing cells, tissues, and organs to communicate with one another.