Biomolecules: Proteins & Lipids
COMPREHENSIVE STUDY & LECTURE NOTES
1. Classification of Proteins
On the basis of molecular structure, proteins are classified into two primary types:
a. Fibrous Proteins
• Structure: Polypeptide chains are twisted around each other to form a long, fiber-like linear structure.
• Solubility: Highly insoluble in water or any other common chemical reagents.
• Occurrence: Primarily found structural materials of animals.
• Examples: Keratin (found in skin, hair, nails), Collagen (found in muscles, tendons, and connective
tissues).
b. Globular Proteins
• Structure: Consists of one or more polypeptide chains folded tightly together into spherical or globular
shapes.
• Stabilization: Folded chains are stabilized and linked together via Hydrogen bonds (H₂ bonds).
• Solubility: Soluble in water, aqueous solutions of acids, bases, etc.
• Occurrence: Found commonly in both plants and animals, governing active metabolic functions.
• Examples: Albumin, Globulin (found in maize, rice, wheat).
2. Levels of Protein Structure
Proteins display complex three-dimensional arrangements. There are 4 distinct structural levels:
(1) Primary Structure
In this structure, amino acids (AA) are organized sequentially in a straight linear chain. They are linked
together via strong covalent bonds known as peptide bonds.
AA — AA — AA — AA — AA
(Linear sequence linked via peptide bonds; e.g., Insulin)
Biomolecules Study Guide: Proteins & Lipids 1
COMPREHENSIVE STUDY & LECTURE NOTES
1. Classification of Proteins
On the basis of molecular structure, proteins are classified into two primary types:
a. Fibrous Proteins
• Structure: Polypeptide chains are twisted around each other to form a long, fiber-like linear structure.
• Solubility: Highly insoluble in water or any other common chemical reagents.
• Occurrence: Primarily found structural materials of animals.
• Examples: Keratin (found in skin, hair, nails), Collagen (found in muscles, tendons, and connective
tissues).
b. Globular Proteins
• Structure: Consists of one or more polypeptide chains folded tightly together into spherical or globular
shapes.
• Stabilization: Folded chains are stabilized and linked together via Hydrogen bonds (H₂ bonds).
• Solubility: Soluble in water, aqueous solutions of acids, bases, etc.
• Occurrence: Found commonly in both plants and animals, governing active metabolic functions.
• Examples: Albumin, Globulin (found in maize, rice, wheat).
2. Levels of Protein Structure
Proteins display complex three-dimensional arrangements. There are 4 distinct structural levels:
(1) Primary Structure
In this structure, amino acids (AA) are organized sequentially in a straight linear chain. They are linked
together via strong covalent bonds known as peptide bonds.
AA — AA — AA — AA — AA
(Linear sequence linked via peptide bonds; e.g., Insulin)
Biomolecules Study Guide: Proteins & Lipids 1
