Biomolecules: Proteins, Carbs, Lipids, Nucleic Acids & Enzymes GK Guide

Biomolecules are organic compounds that are essential for the survival and functioning of all living organisms. They are primarily composed of carbon, hydrogen, oxygen, nitrogen, and sometimes phosphorus or sulphur. The four major classes of biomolecules are carbohydrates, proteins, lipids, and nucleic acids, along with enzymes which act as biological catalysts to speed up chemical reactions in the body.

This topic is a high-yield area for the General Science section of WBCS, SSC, Railway, Banking, and UPSC examinations. Questions frequently test the basic building blocks of these molecules, their functions, and common deficiency-related facts. This article covers the fundamental properties, classification, key examples, and a special West Bengal connection to help you retain these concepts for your upcoming competitive exams.

Carbohydrates

Definition and Types

Carbohydrates are organic compounds with the general formula Cₙ(H₂O)ₙ. They are the primary and most immediate source of energy for the human body.

• Monosaccharides: Simplest sugars that cannot be hydrolysed further (e.g., Glucose, Fructose, Galactose).
• Disaccharides: Formed by the linkage of two monosaccharides (e.g., Sucrose = Glucose + Fructose; Lactose = Glucose + Galactose; Maltose = Glucose + Glucose).
• Polysaccharides: Complex carbohydrates with long chains (e.g., Starch in plants, Glycogen in animals, Cellulose in plant cell walls).

Proteins

Structure and Function

Proteins are polymers made up of amino acids linked by peptide bonds. There are 20 standard amino acids, out of which 9 are essential and must be obtained from the diet.

• Structural Proteins: Provide physical support (e.g., Keratin in hair and nails, Collagen in connective tissue).
• Functional Proteins: Perform dynamic roles (e.g., Haemoglobin for oxygen transport, Insulin for blood sugar regulation, Antibodies for immunity).
• Denaturation: The loss of a protein's 3D structure and biological function due to extreme heat or pH changes (e.g., the solidifying of egg white when boiled).

Lipids

Types and Roles

Lipids are hydrophobic (water-insoluble) molecules that serve as long-term energy storage and structural components of cell membranes.

Type	Structure	Function / Example
Triglycerides	1 Glycerol + 3 Fatty Acids	Main form of stored energy in animals (fats) and plants (oils).
Phospholipids	1 Glycerol + 2 Fatty Acids + 1 Phosphate	Major component of the cell membrane (forms the lipid bilayer).
Steroids	Fused four-ring carbon structure	Signalling molecules and hormones like cholesterol, testosterone, and oestrogen.

Nucleic Acids

DNA and RNA

Nucleic acids are polymers of nucleotides. Each nucleotide consists of a pentose sugar, a phosphate group, and a nitrogenous base. Understanding the molecular basis of life is crucial for modern biology. For broader scientific context, you can explore how fundamental research is supported in India through initiatives like the VAIBHAV Fellowship connecting Indian-origin scientists.

• DNA (Deoxyribonucleic Acid): Double-stranded helix. Sugar is deoxyribose. Bases: Adenine (A), Thymine (T), Cytosine (C), Guanine (G). A pairs with T, C pairs with G.
• RNA (Ribonucleic Acid): Usually single-stranded. Sugar is ribose. Bases: Adenine (A), Uracil (U), Cytosine (C), Guanine (G). A pairs with U.

Enzymes

Properties and Mechanism

Enzymes are biological catalysts, mostly proteins, that speed up chemical reactions without being consumed in the process.

• Specificity: Follows the "lock and key" model; each enzyme acts on a specific substrate.
• Optimum Conditions: Work best at specific temperatures (usually 37°C in humans) and specific pH levels.
• Naming Convention: Usually end with the suffix "-ase" (e.g., Amylase breaks down starch, Lipase breaks down lipids, Pepsin breaks down proteins in the stomach).

West Bengal Connection in Biomolecular Research

• Indian Institute of Chemical Biology (IICB), Kolkata: A premier constituent laboratory of the Council of Scientific and Industrial Research (CSIR). It focuses extensively on biomolecules, drug discovery, and molecular biology.
• Bose Institute, Kolkata: One of the oldest research institutes in India, established in 1917 by Sir Jagadish Chandra Bose, currently conducting advanced research in protein folding and biomolecular sciences.
• Biotechnology Hub: West Bengal is emerging as a key hub for biotechnology, linking fundamental biomolecular studies to practical applications in agriculture and ecosystem conservation.

Quick Comparison of Biomolecules

Biomolecule	Building Block	Bond Type	Primary Function
Carbohydrate	Monosaccharide	Glycosidic bond	Immediate energy source
Protein	Amino Acid	Peptide bond	Structure, transport, catalysis
Lipid	Fatty Acid + Glycerol	Ester bond	Long-term energy storage, membranes
Nucleic Acid	Nucleotide	Phosphodiester bond	Genetic information storage

For a strong foundation in measurement and basic scientific principles that underpin these biological concepts, refer to our guide on Units, Dimensions and Newton's Laws of Motion.

Q1. Which of the following is the building block of proteins?
(a) Monosaccharide
(b) Amino acid
(c) Nucleotide
(d) Fatty acid

Answer: (b) – Proteins are polymers made up of amino acids linked by peptide bonds.

Q2. Which sugar is commonly known as blood sugar?
(a) Glucose
(b) Fructose
(c) Sucrose
(d) Lactose

Answer: (a) – Glucose is the primary sugar circulating in the blood, providing immediate energy to cells.

Q3. The bond linking two amino acids in a protein is called:
(a) Glycosidic bond
(b) Ester bond
(c) Peptide bond
(d) Hydrogen bond

Answer: (c) – A peptide bond forms between the carboxyl group of one amino acid and the amino group of another.

Q4. Which of the following is NOT a polysaccharide?
(a) Starch
(b) Glycogen
(c) Cellulose
(d) Sucrose

Answer: (d) – Sucrose is a disaccharide, while starch, glycogen, and cellulose are complex polysaccharides.

Q5. In DNA, Adenine always pairs with:
(a) Cytosine
(b) Guanine
(c) Thymine
(d) Uracil

Answer: (c) – In DNA, Adenine (A) forms two hydrogen bonds specifically with Thymine (T).

Q6. Which biomolecule is the major structural component of the cell membrane?
(a) Carbohydrates
(b) Phospholipids
(c) Nucleic acids
(d) Polysaccharides

Answer: (b) – Phospholipids form the lipid bilayer, which is the fundamental barrier of all cell membranes.

Q7. Enzymes are primarily composed of:
(a) Lipids
(b) Carbohydrates
(c) Proteins
(d) Nucleic acids

Answer: (c) – Most enzymes are proteins, although some RNA molecules (ribozymes) also have catalytic activity.

Q8. Which of the following institutes in Kolkata is a premier CSIR laboratory for biomolecular research?
(a) Indian Statistical Institute
(b) Indian Institute of Chemical Biology (IICB)
(c) S.N. Bose National Centre for Basic Sciences
(d) Victoria Institution

Answer: (b) – IICB is a leading CSIR laboratory in Kolkata focused on chemical biology and biomolecular research.

Q9. The storage form of carbohydrate in the human liver is:
(a) Starch
(b) Cellulose
(c) Glycogen
(d) Sucrose

Answer: (c) – Glycogen is the multibranched polysaccharide of glucose that serves as a form of energy storage in animals.

Q10. Which nitrogenous base is present in RNA but absent in DNA?
(a) Adenine
(b) Thymine
(c) Uracil
(d) Cytosine

Answer: (c) – RNA contains Uracil (U) instead of Thymine (T), which is exclusively found in DNA.

Q11. What is the general chemical formula for carbohydrates?
(a) Cₙ(H₂O)ₙ
(b) CₙH₂ₙ₊₂
(c) CH₄
(d) C₆H₁₂O₆N₂

Answer: (a) – Carbohydrates are hydrates of carbon, generally following the formula Cₙ(H₂O)ₙ.

Q12. Which enzyme is responsible for breaking down starch in the human mouth?
(a) Pepsin
(b) Lipase
(c) Salivary Amylase
(d) Trypsin

Answer: (c) – Salivary amylase (ptyalin) initiates the digestion of starch into maltose in the mouth.

Q13. Lipids are characterized by their:
(a) High solubility in water
(b) Insolubility in water and solubility in organic solvents
(c) High nitrogen content
(d) Polymeric nature

Answer: (b) – Lipids are hydrophobic molecules, meaning they do not dissolve in water but dissolve in organic solvents like ether.

Q14. The loss of biological activity of a protein due to heat or pH change is called:
(a) Denaturation
(b) Hydrolysis
(c) Polymerisation
(d) Condensation

Answer: (a) – Denaturation disrupts the secondary and tertiary structure of proteins, leading to a loss of function.

Q15. Which of the following is an example of a structural protein?
(a) Insulin
(b) Haemoglobin
(c) Keratin
(d) Amylase

Answer: (c) – Keratin is a fibrous structural protein found in hair, nails, feathers, and horns.

Q16. How many essential amino acids must be obtained from the human diet?
(a) 5
(b) 9
(c) 12
(d) 20

Answer: (b) – There are 9 essential amino acids that the human body cannot synthesize and must get from food.

Q17. The bond connecting nucleotides in a nucleic acid chain is:
(a) Peptide bond
(b) Glycosidic bond
(c) Phosphodiester bond
(d) Ester bond

Answer: (c) – Nucleotides are linked together by phosphodiester bonds between the sugar of one nucleotide and the phosphate of the next.

Q18. Which of the following is a disaccharide?
(a) Glucose
(b) Fructose
(c) Lactose
(d) Starch

Answer: (c) – Lactose is a disaccharide composed of glucose and galactose, commonly found in milk.

Q19. Ribosomes, the site of protein synthesis in a cell, are primarily made of:
(a) DNA and lipids
(b) Lipids and polysaccharides
(c) Carbohydrates and DNA
(d) rRNA and proteins

Answer: (d) – Ribosomes are complex molecular machines composed of ribosomal RNA (rRNA) and ribosomal proteins.

Q20. Which vitamin group acts as a coenzyme in many metabolic reactions involving biomolecules?
(a) Vitamin C
(b) Vitamin B complex
(c) Vitamin D
(d) Vitamin K

Answer: (b) – B-complex vitamins (like B1, B2, B3, B6, B12) are crucial precursors for coenzymes in metabolic pathways.

Focus on the building blocks of each biomolecule, the specific bonds that link them (peptide, glycosidic, ester, phosphodiester), and their primary biological functions. Pay special attention to enzyme naming conventions, DNA vs. RNA differences, and the role of Kolkata-based institutes like IICB in biomolecular research. Regular revision of these core concepts will help you easily tackle General Science questions in WBCS, SSC, and Railway exams. For more daily updates and study materials, visit CrackGK. Reference: NCERT Class 11 Biology (Chapter 9: Biomolecules) and NCERT Class 12 Chemistry (Chapter 14: Biomolecules).