Category Archives: Proteins

biological chemistry

Difference between Collagen and Keratin – Comparison Table

Collagen vs Keratin

Collagen vs Keratin
(Similarities and Differences between Collagen and Keratin)

Collagen and Keratin are the main structural proteins. They are two main families of fibrous proteins and are abundantly present in the extracellular matrix and various connective tissues in animals. 

Collagen: A linear structural fibrous protein abundantly found in the connective tissue and extracellular space of the cells. They are also found in tendons, ligaments, cornea, cartilage, bone, blood vessels, intervertebral discs and the dentine in teeth.

Keratin: A structural protein abundantly present in epithelial cells. They protect the epithelial cells from damage or stress. Keratin is also present in appendages such as feathers, hairs and nail, horn, claws and hooves of animals. Keratin is the structural material that makes the human skin.

The present post discusses the similarities and Differences between Collagen and Keratin with a Comparison Table.

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biological chemistry

Chemical Bonds Involved in Protein Structure and Conformation

bonds stabilizing protein structure

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Bonds involved in Protein Structure
(Bonds Stabilizing the Primary, Secondary, Tertiary and Quaternary Structure of Proteins)

Proteins are the polymers of amino acids. Amino acids are joined together by a special type of covalent bond (peptide bond) to form linear structures called polypeptides. The polypeptides are then folded into specific structures to form the functional conformation of the protein. The folding of proteins into specific shapes and conformations are assisted and stabilized by many types of bonds in them. Some of these bonds are strong bonds whereas others are weak interactions. Important types of bonds involved in protein structure and conformation are Peptide bonds, Ionic bonds, Disulfide bonds, Hydrogen bonds and Hydrophobic Interactions. The current post describes the importance of each of these bonds and their role in the functional conformation of the protein.

What are the different types of bonds present in a protein?

Ø  Typically, proteins possess the following FIVE types of bonds.

(1).    Peptide bond

(2).   Ionic bond

(3).   Disulfide bond

(4).   Hydrogen bond

(5).   Hydrophobic Interactions

(1). Peptide Bond

Ø  Peptide bond definition: a covalent bond formed between the carboxylic group of one amino acid and the amino group of another amino acid.

Ø  Peptide bond is a strong covalent bond with high bond dissociation energy.

Ø  It is formed by the joining of two amino acid residues during protein synthesis.

Ø  The carboxylic group (- COOH) of one amino acid combine with the amino group (-NH2) of another amino acid to form the peptide bond.

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biological chemistry

Classification of Proteins Based on Structure and Function

protein classification

Classification of Proteins

Proteins are important macromolecules of the cells, formed by the polymerization of amino acids according to the sequence of genetic code in the mRNA. Proteins are the mode of expression of the genetic information. They perform a variety of duties in the cells such as they act as the structural components of cells, enzymes, hormones, pigments, storage proteins and some toxins in the cells. The proteins are classified into many categories based on different criterions.

Criterion for the classification of proteins:

Ø  Proteins are classified based on the following THREE criterions:

                             (I).     Classification based on STRUCTURE of Protein

                            (II).    Classification based on COMPOSITION of Protein

                           (III).    Classification based on FUNCTIONS of Proteins

(I). Classification of Proteins based on the Structure of Proteins

Ø  Based on the structure, proteins are classified into 3 groups.

(A).   Fibrous Proteins

(B).   Globular Proteins

(C).   Intermediate Proteins

(A). Fibrous Proteins

Ø  They are linear (long fibrous) in shape.

Ø  Secondary structure is the most important functional structure of fibrous proteins.

Ø  Usually, these proteins do not have tertiary structures.

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