Biomolecules are the chemical compounds present in living organisms that perform essential biological functions. These molecules are responsible for the structure, function, and regulation of cells and tissues.
All living systemsβfrom bacteria to humansβare built from biomolecules. They include:
- Carbohydrates
- Proteins
- Nucleic acids
- Vitamins
π Core Idea: Life is essentially a network of chemical reactions controlled and carried out by biomolecules.
1. Carbohydrates (Energy Molecules)
Definition
Carbohydrates are organic compounds composed of carbon, hydrogen, and oxygen, generally in the ratio:
Cβ(HβO)ᡧ
They are the primary source of energy for living organisms.
Classification of Carbohydrates
(A) Monosaccharides
These are the simplest carbohydrates that cannot be hydrolyzed further.
Examples:
- Glucose
- Fructose
- Ribose
Structure of Glucose
Open Chain Structure
CHO β (CHOH)β β CHβOH
- Contains an aldehyde group (βCHO)
- Has multiple hydroxyl groups (βOH)
Cyclic Structure of Glucose
Glucose exists mainly in cyclic form due to intramolecular reaction.
Key Points:
- Forms a six-membered ring (pyranose form)
- Exists as:
- Ξ±-glucose
- Ξ²-glucose
Concept Clarity
π WHY glucose forms a ring?
Because the aldehyde group reacts with the hydroxyl group within the same molecule.
(B) Disaccharides
Formed by the combination of two monosaccharides through a glycosidic bond.
Examples:
- Sucrose = Glucose + Fructose
- Maltose = Glucose + Glucose
- Lactose = Glucose + Galactose
Glycosidic Linkage
A bond formed between two monosaccharides with the elimination of water.
(C) Polysaccharides
Complex carbohydrates made of many monosaccharide units.
Examples:
- Starch β energy storage in plants
- Glycogen β energy storage in animals
- Cellulose β structural component of plants
Concept Clarity
π WHY cellulose is not digestible in humans?
Because humans lack the enzyme required to break Ξ²-glycosidic bonds.
2. Proteins (Body Building Molecules)
Definition
Proteins are polymers of amino acids linked by peptide bonds.
They are responsible for:
- Growth and repair
- Enzyme activity
- Structural support
Amino Acids
General Structure
HβN β CH(R) β COOH
Where:
- NHβ β amino group
- COOH β carboxyl group
- R β side chain
Types of Amino Acids
Essential Amino Acids
Must be obtained from diet
Non-Essential Amino Acids
Synthesized by body
Peptide Bond
Formed when:
- COOH of one amino acid reacts with NHβ of another
Resulting bond:
βCOβNHβ
Structure of Proteins
1. Primary Structure
Sequence of amino acids
2. Secondary Structure
- Ξ±-helix
- Ξ²-pleated sheet
3. Tertiary Structure
3D folding due to interactions
4. Quaternary Structure
Multiple polypeptide chains
Denaturation of Proteins
Definition
Loss of native structure due to heat or chemicals.
Effects:
- Loss of biological activity
Concept Clarity
π WHY proteins lose function on heating?
Because their 3D structure gets destroyed.
3. Enzymes (Biological Catalysts)
Definition
Enzymes are proteins that speed up biochemical reactions.
Characteristics
- Highly specific
- Work at optimum pH and temperature
- Not consumed in reactions
Example
- Amylase β breaks starch
- Pepsin β digests proteins
Mechanism of Enzyme Action
Enzymes have an active site where substrate binds.
π Lock and key model explains specificity.
Concept Clarity
π WHY enzymes are specific?
Because only specific molecules fit into their active site.
4. Nucleic Acids (Genetic Material)
Definition
Nucleic acids are biomolecules that store and transmit genetic information.
Types
- DNA (Deoxyribonucleic Acid)
- RNA (Ribonucleic Acid)
Components of Nucleotides
Each nucleotide contains:
- Nitrogenous base
- Pentose sugar
- Phosphate group
Nitrogen Bases
- Adenine (A)
- Guanine (G)
- Cytosine (C)
- Thymine (T)
- Uracil (U)
DNA Structure
- Double helix
- Two strands twisted
- Complementary base pairing
Base Pairing Rules
- A = T
- G β‘ C
RNA Structure
- Single-stranded
- Contains uracil instead of thymine
Concept Clarity
π WHY DNA is stable?
Because of hydrogen bonding between base pairs.
5. Vitamins (Protective Biomolecules)
Definition
Vitamins are organic compounds required in small amounts for normal body functioning.
Classification
(A) Fat-Soluble Vitamins
- Vitamin A
- Vitamin D
- Vitamin E
- Vitamin K
Stored in body
(B) Water-Soluble Vitamins
- Vitamin B complex
- Vitamin C
Not stored β need regular intake
Deficiency Diseases
| Vitamin | Disease |
|---|---|
| A | Night blindness |
| B1 | Beriberi |
| C | Scurvy |
| D | Rickets |
Concept Clarity
π WHY vitamin C deficiency causes scurvy?
Because it is needed for collagen formation.
6. Hormones (Brief Overview)
Definition
Hormones are chemical messengers that regulate body functions.
Examples
- Insulin β controls blood sugar
- Thyroxine β regulates metabolism
7. Important Reactions
Glucose Reactions
- Oxidation β forms gluconic acid
- Reduction β forms sorbitol
Protein Reactions
- Hydrolysis β amino acids
8. Differences (Exam Important)
DNA vs RNA
| DNA | RNA |
|---|---|
| Double stranded | Single stranded |
| Contains thymine | Contains uracil |
| Stable | Less stable |
Starch vs Cellulose
| Starch | Cellulose |
|---|---|
| Digestible | Not digestible |
| Energy storage | Structural |
9. Important Points for Exams
- Glucose (open + cyclic structure)
- Peptide bond formation
- DNA base pairing
- Vitamin deficiencies
- Enzyme properties
10. Concept Clarity Section (Very Important)
π WHY biomolecules are essential?
Because they perform all life processes.
π WHY carbohydrates are energy sources?
Because they break down easily to release energy.
π WHY proteins are called building blocks?
Because they form tissues and enzymes.
π WHY nucleic acids are important?
Because they store genetic information.
11. Common Mistakes
- Confusing DNA and RNA
- Mixing Ξ± and Ξ² glucose
- Forgetting glycosidic bond
- Ignoring peptide bond
Conclusion
Biomolecules form the chemical foundation of life. Understanding their structure and function helps in mastering both chemistry and biology concepts.
This chapter is highly scoring because it is:
- Concept-based
- Easy to understand
- Frequently asked in exams
π Focus on structures + functions + examples + concept clarity.