01Introduction to biomolecules class 12 chemistry
Mastering the concepts of biomolecules class 12 chemistry is fundamental for any medical aspirant aiming to excel in NEET. Biomolecules are the organic compounds that form the basis of life, driving the complex chemical processes within living organisms. From providing energy through carbohydrates to carrying genetic information via nucleic acids, these molecules are the building blocks of every biological entity. In this guide, we provide a high-yield summary of the entire chapter to boost your NEET percentile.
Living systems are composed of various complex organic compounds such as carbohydrates, proteins, enzymes, lipids, vitamins, and nucleic acids. These molecules interact with each other and constitute the molecular logic of life processes. Understanding their structure, classification, and chemical properties is a major focus area for competitive entrance examinations.
02Classification in biomolecules class 12 chemistry: Carbohydrates
Carbohydrates, also known as saccharides, are polyhydroxy aldehydes or ketones or compounds which produce them on hydrolysis. They are the most abundant biomolecules on Earth and serve as the primary energy source for most organisms.
| Class | Definition | Examples |
|---|---|---|
| Monosaccharides | Cannot be hydrolyzed further into simpler units. | Glucose, Fructose, Ribose |
| Oligosaccharides | Yield 2 to 10 monosaccharide units on hydrolysis. | Sucrose, Maltose, Lactose |
| Polysaccharides | Large polymers yielding many monosaccharide units. | Starch, Cellulose, Glycogen |
Structure and Reactions of Glucose
Glucose (C6H12O6) is an aldohexose. Its structure consists of an aldehyde group and five hydroxyl groups. In aqueous solution, it predominantly exists in cyclic forms known as α-D-glucopyranose and β-D-glucopyranose.
Glucose + Conc. HNO3 → Saccharic Acid
03Proteins and Amino Acids
Proteins are the most versatile biomolecules class 12 chemistry students study. They are polymers of α-amino acids linked by peptide bonds. Amino acids contain both an amino (−NH2) and a carboxyl (−COOH) group attached to the same carbon atom.
(In neutral solution, amino acids exist as dipolar ions called Zwitterions.)
Classification of Amino Acids
- Essential: Cannot be synthesized by the body; must be taken through diet (e.g., Valine, Leucine).
- Non-essential: Can be synthesized by the body (e.g., Glycine, Alanine).
- Acidic: Contain extra −COOH (Aspartic acid).
- Basic: Contain extra −NH2 (Lysine).
04Structural Levels of Proteins
The complexity of protein architecture is divided into four levels. This is a high-yield conceptual area for biomolecules class 12 chemistry MCQ practice.
05Vitamins and Deficiency Diseases
Vitamins are essential micronutrients required in small amounts for normal growth and health. A detailed table of vitamins is a staple for any biomolecules class 12 chemistry student.
| Vitamin | Solubility | Deficiency Disease |
|---|---|---|
| Vitamin A (Retinol) | Fat Soluble | Xerophthalmia, Night Blindness |
| Vitamin D (Calciferol) | Fat Soluble | Rickets (children), Osteomalacia |
| Vitamin C (Ascorbic Acid) | Water Soluble | Scurvy (bleeding gums) |
| Vitamin B12 | Water Soluble | Pernicious Anemia |
| Vitamin K | Fat Soluble | Increased blood clotting time |
06Nucleic Acids in biomolecules class 12 chemistry
Nucleic acids are the biopolymers responsible for the storage and transmission of genetic information. There are two types: DNA (Deoxyribonucleic acid) and RNA (Ribonucleic acid). They are composed of nucleotides, which consist of a pentose sugar, a nitrogenous base, and a phosphate group.
Nucleotide = Sugar + Base + Phosphate
DNA vs RNA
- Sugar: DNA has 2-deoxyribose; RNA has ribose.
- Bases: DNA uses Adenine, Guanine, Cytosine, and Thymine. RNA uses Uracil instead of Thymine.
- Structure: DNA is a double helix; RNA is usually single-stranded.
- Base Pairing: A pairs with T (2 H-bonds) and G pairs with C (3 H-bonds) in DNA.
07Enzymes and Hormones
Enzymes are biological catalysts that speed up chemical reactions with incredible specificity. They generally work by lower the activation energy of a reaction through the “Lock and Key” mechanism.
Hormones are chemical messengers produced in ductless glands and transported by blood to target organs. They help maintain biological balance (homeostasis). Examples include insulin (regulates blood sugar) and adrenaline (prepares body for stress).
Quick Revision Summary
- Carbohydrates: General formula Cx(H2O)y. Classified into mono, oligo, and polysaccharides.
- Glucose: An aldohexose; reduces Tollens’ and Fehling’s reagents.
- Sucrose: Invert sugar; gives glucose and fructose on hydrolysis.
- Glycosidic Linkage: Bond between two monosaccharide units through oxygen.
- Amino Acids: Bifunctional molecules; α-amino acids build proteins.
- Peptide Bond: −CO−NH− linkage between amino acids.
- Fibrous Proteins: Water-insoluble (Keratin, Myosin).
- Globular Proteins: Water-soluble (Insulin, Albumin).
- DNA bases: A, G, C, T. RNA bases: A, G, C, U.
- Vitamin C: Heat-labile; must be supplemented daily as it is water-soluble.
08Frequently Asked Questions
What is the difference between a nucleoside and a nucleotide?
Why is sucrose called invert sugar?
What happens during the denaturation of proteins?
Why are vitamins A, D, E, and K called fat-soluble?
What is a glycosidic linkage?
How do enzymes differ from inorganic catalysts?
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Table of Contents
Chemistry — Class 12
| 01 | Solutions | Go to page |
| 02 | Electrochemistry | Go to page |
| 03 | Chemical Kinetics | Go to page |
| 04 | d- and f-Block Elements | Go to page |
| 05 | Coordination Compounds | Go to page |
| 06 | Haloalkanes and Haloarenes | Go to page |
| 07 | Alcohols, Phenols and Ethers | Go to page |
| 08 | Aldehydes, Ketones and Carboxylic Acids | Go to page |
| 09 | Amines | Go to page |
| 10 | Biomolecules | Go to page |