biological chemistry

Structure of Proteins (Biochemistry Lecture Notes)

protein structure

Protein Structure
(Primary, Secondary, Tertiary & Quaternary Structure of Proteins)

Learning objectives: Protein Structure: Primary Structure, Secondary Structure (Alpha Helix, Beta Plates, Beta Turns), Tertiary Structure, Quaternary Structure, Bonds Stabilizing different Protein Structures.

Protein Structure

Ø  Proteins are the polymers of amino acids. Individual amino acids (residues) are joined by peptide bonds to form the linear polypeptide chain. This linear polypeptide chain is folded into specific structural conformations or simply ‘structure’.  A protein can have up to four levels of structural conformations. Previously we have discussed but the ‘Bonds involved in Protein Structure”. In the present post, we will discuss different types of protein structures.

Ø  A protein can have Four levels of structural organization:

Ø  They are designated as:

(1). Primary Structure

(2). Secondary Structure

(3). Tertiary Structure

(4). Quaternary Structure

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mcq biology

Biochemistry MCQ on Proteins-Structure and Functions (Biochemistry MCQ 15)

Proteins questions for net exam

Biochemistry MCQ – 15
(Biology / Life Sciences MCQ: Multiple Choice Questions in Biochemistry)

(Sample/Model/Practice Questions for CSIR JRF/NET Life Science Examination, ICMR JRF Exam, DBT BET JRF Exam, GATE BT and XL Exam, ICAR JRF NE Exam, PG Entrance Exam, JAM Exam, GS Biology Exam and Medical Entrance Exam)

MCQ Biology Lecture Notes

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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

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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