HSSLIVE Plus One Zoology Chapter 4: Biomolecules Notes – Hsslive | Hsslive.co.in | Hss Live

Biomolecules are the organic compounds that form the molecular basis of life. This chapter investigates the four major classes of biomolecules: carbohydrates, proteins, lipids, and nucleic acids. It examines their chemical structures, physical properties, and biological functions, as well as how these molecules interact in metabolic pathways. The chapter also covers enzymes—specialized proteins that catalyze biochemical reactions—explaining their mechanism of action and their crucial role in cellular metabolism.

Chapter 4: Biomolecules

Introduction to Biomolecules

Biomolecules are organic compounds present in living organisms. They include macromolecules like proteins, carbohydrates, lipids, and nucleic acids, as well as smaller molecules like vitamins, hormones, and metabolites.

Chemical Composition of Living Cells

Living organisms are made up of approximately 70% water, while the remaining 30% consists of carbon-containing compounds. The major elements in biomolecules are carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur (CHONPS).

Primary and Secondary Metabolites

Primary Metabolites: Essential for normal growth, development, and reproduction (proteins, carbohydrates, lipids, nucleic acids)
Secondary Metabolites: Not directly involved in normal growth but often have ecological or defensive roles (alkaloids, flavonoids, rubber, resins)

Carbohydrates

Carbohydrates are composed of carbon, hydrogen, and oxygen, typically with the formula (CH₂O)n.

Classification of Carbohydrates:

Monosaccharides: Simple sugars that cannot be hydrolyzed further
- Examples: Glucose, fructose, galactose (hexoses – 6 carbon)
- Examples: Ribose, deoxyribose (pentoses – 5 carbon)
- Properties: Sweet taste, crystalline, soluble in water
Disaccharides: Two monosaccharides joined by glycosidic bond
- Examples: Sucrose (glucose + fructose), lactose (glucose + galactose), maltose (glucose + glucose)
- Hydrolyzed to simple sugars by digestive enzymes
Polysaccharides: Many monosaccharides joined together
- Examples: Starch, glycogen (storage), cellulose (structural)
- Usually tasteless, non-crystalline, form colloidal solutions

Functions of Carbohydrates:

Energy source (glucose is the primary fuel)
Storage of energy (starch in plants, glycogen in animals)
Structural components (cellulose in plant cell walls, chitin in arthropod exoskeletons)
Cell recognition and adhesion (glycoproteins)

Proteins

Proteins are polymers of amino acids joined by peptide bonds.

Amino Acids:

Building blocks of proteins
Contains amino group (-NH₂), carboxyl group (-COOH), and R-group (side chain)
20 different amino acids commonly found in proteins
Essential amino acids cannot be synthesized by the body and must be obtained from diet

Structure of Proteins:

Primary Structure: Sequence of amino acids
Secondary Structure: Regular folding patterns (α-helix, β-pleated sheet)
Tertiary Structure: Three-dimensional folding of the polypeptide chain
Quaternary Structure: Association of multiple polypeptide chains

Functions of Proteins:

Structural components (collagen, keratin)
Enzymes (biological catalysts)
Transport (hemoglobin, transferrin)
Defense (antibodies)
Hormones (insulin, growth hormone)
Contractile proteins (actin, myosin)
Regulatory proteins (histones)

Lipids

Lipids are diverse biomolecules that are insoluble in water but soluble in organic solvents.

Types of Lipids:

Simple Lipids: Esters of fatty acids with alcohols
- Fats and oils (triglycerides): Glycerol + 3 fatty acids
- Waxes: Long-chain alcohol + fatty acid
Compound Lipids: Lipids with additional groups
- Phospholipids: Main components of cell membranes
- Glycolipids: Found in cell membranes, especially nerve tissues
- Lipoproteins: Transport lipids in blood
Derived Lipids: Hydrolysis products of simple and compound lipids
- Steroids: Cholesterol, sex hormones, adrenal hormones
- Prostaglandins: Hormone-like substances

Functions of Lipids:

Energy storage (fats store more energy than carbohydrates)
Structural components of cell membranes
Insulation and protection of organs
Vitamins A, D, E, K are fat-soluble
Hormones (steroids)

Nucleic Acids

Nucleic acids are polymers of nucleotides that store and transmit genetic information.

Types of Nucleic Acids:

DNA (Deoxyribonucleic Acid):
- Double-helix structure
- Contains deoxyribose sugar, phosphate, and nitrogenous bases (A, T, G, C)
- Stores genetic information
RNA (Ribonucleic Acid):
- Usually single-stranded
- Contains ribose sugar, phosphate, and nitrogenous bases (A, U, G, C)
- Types: mRNA, tRNA, rRNA
- Involved in protein synthesis

Functions of Nucleic Acids:

Storage of genetic information (DNA)
Transmission of genetic information (DNA replication)
Protein synthesis (DNA → RNA → Protein)
Gene regulation

Enzymes

Enzymes are biological catalysts, mostly proteins, that accelerate biochemical reactions.

Characteristics of Enzymes:

High specificity for substrates
Efficient catalysis without being consumed
Function optimally at specific temperature and pH
Can be regulated (activators, inhibitors)

Mechanism of Enzyme Action:

Substrate binds to the active site of enzyme (enzyme-substrate complex)
Reaction occurs
Products are released
Enzyme is ready for next reaction

Enzyme Classification:

Oxidoreductases: Catalyze oxidation-reduction reactions
Transferases: Transfer functional groups
Hydrolases: Catalyze hydrolysis reactions
Lyases: Add or remove groups without hydrolysis
Isomerases: Catalyze isomerization reactions
Ligases: Join two molecules using ATP energy

Complete Chapter-wise Hsslive Plus One Zoology Notes

Our HSSLive Plus One Zoology Notes cover all chapters with key focus areas to help you organize your study effectively: