Introduction
Imagine your body as a complex machine. Just like a car needs fuel, oil, and various parts to function, our body needs special molecules to grow, repair, and function properly. These special molecules are called biomolecules - the building blocks of life!
The four major types of biomolecules are carbohydrates, lipids, proteins, and nucleic acids. In this post, we'll break down these essential biomolecules into simple, easy-to-understand sections with clear examples and tables that will help you remember key facts for your exams.
In competitive exams like UPSC, SSC, Railway, and Delhi Police, questions about biomolecules appear regularly in the General Science and Biology sections.
What Are Biomolecules?
Biomolecules are organic
molecules produced by living organisms that are necessary for
their growth, development, and functioning.
They are made up of carbon
(C), hydrogen (H), oxygen (O), nitrogen (N), and sometimes phosphorus (P) and sulfur (S).
Classification of Biomolecules:
|
Type |
Monomer/unit |
Key functions |
Common examples |
Indian food links |
|
Carbohydrates |
Monosaccharides |
Quick energy, energy storage, fiber |
Glucose, starch, cellulose |
Rice, chapati, potato |
|
Lipids |
Fatty acids + glycerol |
Long-term energy, membranes, hormones |
Triglycerides, phospholipids, cholesterol |
Oil, ghee, nuts |
|
Proteins |
Amino acids |
Enzymes, structure, transport, defense |
Hemoglobin, enzymes, antibodies |
Dal, paneer, eggs |
|
Nucleic acids |
Nucleotides |
Store and express genetic information |
DNA, RNA |
Found in all cells/foods |
Carbohydrates
What are Carbohydrates?
Carbohydrates are organic compounds made up of carbon, hydrogen, and oxygen,
usually in a ratio close to 1:2:1 (for example, C6H12O6 for glucose). They are
found in foods like rice, wheat, potatoes, fruits, and vegetables, and can be
classified by the size and complexity of their molecules.
Types
of Carbohydrates:
|
Type |
Building Block |
Examples |
Main Functions |
|
Monosaccharides |
Single sugar units |
Glucose, Fructose |
Quick energy release |
|
Disaccharides |
2 sugar units |
Sucrose, Lactose |
Energy, sweetness |
|
Oligosaccharides |
3-10 sugar units |
Raffinose, Stachyose |
Cell recognition, prebiotics |
|
Polysaccharides |
Many sugar units |
Starch, Glycogen, Cellulose |
Energy storage, structural support |
1. Monosaccharides:
a. Simplest
carbohydrates (cannot be broken down further).
b. Sweet in taste and water soluble.
Real-life Example: When you eat an apple, the fructose in it provides quick energy to your body.
2. Disaccharides
a. Formed when two monosaccharides combine by condensation reaction
b. Important Disaccharides
(i) Sucrose (Glucose + Fructose): Table sugar
(ii) Lactose (Glucose + Galactose): Milk sugar
(iii) Maltose (Glucose + Glucose): Malt sugar
Real-life Example: The sugar you add to tea is sucrose. Some people
cannot digest lactose (lactose intolerance).
3. Polysaccharides
a. These are complex carbohydrates made of long chains of monosaccharides
b.
Important Polysaccharides:
(i) Starch: Energy storage in plants
(ii) Glycogen: Energy storage in animals (stored in liver and muscles)
(iii) Cellulose: Structural component of plant cell walls (fiber)
(iv) Chitin: Structural component in fungi and arthropods
Real-life Examples: Eating rice or bread (starch) gives you long-lasting energy, Your body stores extra glucose as glycogen in the liver, Eating vegetables provides cellulose (fiber) that helps digestion.
Main Functions of Carbohydrates
a. Energy Source: Main source of fuel for body and brain. Glucose provides fast-release energy.
b. Energy Storage: Excess glucose stored as glycogen in animals or starch in plants for later use.
c. Structural Functions: Cellulose in plants, chitin in fungi and insects for structural integrity.
d. Cell Communication: Oligosaccharides form glycoproteins and glycolipids on cell surfaces, aiding in recognition and signaling.
e. Digestive Health: Dietary fiber, a complex carbohydrate, supports good digestion and gut health.
f. Protein Sparing: Prevents breakdown of proteins for energy if enough carbohydrates are available.
g. Fat Oxidation: Needed for proper fat metabolism, prevents production of harmful ketones.
Carbohydrate Digestion
The process of breaking down complex carbohydrates into simple sugars:
1. Mouth: Salivary amylase breaks down starch into smaller chains
2. Stomach: Acid stops carbohydrate digestion
3. Small Intestine: Pancreatic amylase breaks down carbohydrates into disaccharides
4. Intestinal Wall: Enzymes break disaccharides into monosaccharides
5. Absorption: Monosaccharides are absorbed into the bloodstream
Real-life Example: When you eat a potato (starch), your body breaks it down into glucose, which enters your bloodstream and provides energy to your cells.
Lipids
What are Lipids?
Lipids are a group of naturally occurring molecules that include fats, oils,
waxes, and certain vitamins. They are hydrophobic, meaning they do not dissolve
in water but dissolve in organic solvents like chloroform and alcohol.
Structure
· Made of glycerol and fatty acids.
· Triglycerides = 1 Glycerol + 3 Fatty Acids.
Types of Lipids
|
Type of Lipid |
Examples |
Main Function |
|
Fats and Oils |
Butter, Ghee, Olive Oil |
Energy storage |
|
Phospholipids |
Lecithin |
Cell membrane formation |
|
Steroids |
Cholesterol, Testosterone |
Hormone production and cell structure |
|
Waxes |
Beeswax, Cutin |
Protection and waterproofing |
Simple Fats (Triglycerides)
Simple fats are esters formed by glycerol and three fatty acid molecules. They are the most common form of lipids in our body.
Example: When you eat butter or ghee, you are consuming triglycerides. These are broken down during digestion and stored in adipose tissue for future energy needs.
Saturated vs. Unsaturated Fats
Saturated Fats: These fats have no double bonds between carbon atoms. They are solid at room temperature.
· Examples: Butter, coconut oil, ghee
· Found mainly in animal products
Unsaturated Fats: These fats contain one or more double bonds. They are liquid at room temperature.
· Examples: Olive oil, sunflower oil, fish oil
· Considered healthier for the heart
Phospholipids
Phospholipids are major components of cell membranes. They have a hydrophilic (water-loving) head and hydrophobic (water-fearing) tails. This unique property allows them to form the lipid bilayer in cell membranes.
Example: Lecithin found in egg yolk is a phospholipid used as an emulsifier in food products.
Steroids
Steroids are lipids with a characteristic four-ring structure. Cholesterol is the most common steroid, which serves as a precursor for many hormones.
Example: Cholesterol in our body is used to make vitamin D when skin is exposed to sunlight. It also forms bile acids that help digest fats.
Functions of Lipids
a. Energy Storage: Lipids store energy more efficiently
than carbohydrates
b. Cell Membrane
Structure: Phospholipids form the basic structure of cell
membranes
c. Signaling Molecules:
Hormones like testosterone and estrogen are lipid-based
d. Insulation:
Fat tissue under the skin provides thermal insulation
e. Protection:
Waxes protect plant leaves from water loss
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Protein
What are Protein?
Proteins are large, complex biomolecules made up of amino acids. They are called the "workhorses" of the cell because they perform most cellular functions.
Structure of Proteins
Proteins are polymers of amino acids joined by peptide bonds. There are 20 different amino acids that combine in various sequences to form different proteins.
Example: Hemoglobin in red blood cells is a protein made of 574 amino acids. It carries oxygen from lungs to body tissues.
Levels of Protein Structure
|
Structure Level |
Description |
Example |
|
Primary Structure |
Linear sequence of amino acids |
Chain of amino acids like beads on a string |
|
Secondary Structure |
Local folding into alpha-helix or beta-sheet |
Silk fiber has beta-sheet structure |
|
Tertiary Structure |
3D folding of the entire protein chain |
Myoglobin in muscles |
|
Quaternary Structure |
Multiple protein chains working together |
Hemoglobin has four chains |
Simple Analogy: Think of protein structure like making a woolen sweater:
Primary: Straight wool yarn (amino acid sequence), Secondary: Knitting basic patterns (alpha/beta structures), Tertiary: Shaping into sweater (3D structure), Quaternary: Adding buttons and designs (multiple chains)
Amino Acids: The Building Blocks
Amino acids are the monomers that make up proteins. There are 20 standard amino acids that combine in different sequences to form various proteins.
|
Type |
Number |
Examples |
Characteristics |
|
Essential |
9 |
Valine, Leucine, Isoleucine |
Cannot be made by body, must come from food |
|
Non-essential |
11 |
Glycine, Alanine, Serine |
Can be synthesized by body |
|
Conditionally essential |
6 |
Arginine, Cysteine |
Normally non-essential, but required during illness |
Functions of Proteins
a. Enzymes: Catalyze biochemical reactions (Example: Amylase breaks down starch)
b. Structural Support: Provide strength to tissues (Example: Collagen in skin)
c. Transport: Carry molecules across membranes (Example: Hemoglobin transports oxygen)
d. Defense: Antibodies fight infections (Example: Immunoglobulins)
e. Hormones: Regulate body processes (Example: Insulin controls blood sugar)
f. Movement: Enable muscle contraction (Example: Actin and myosin)
Protein Denaturation
When proteins lose their structure due to heat, pH change, or chemicals, it is called denaturation. Denatured proteins lose their function.
Example: When you boil an egg, the transparent
egg white becomes solid and white. This happens because heat denatures the
albumin protein.
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Nucleic Acids
What Are Nucleic Acids?
Nucleic acids are biomolecules that store and transmit genetic information. There are two types: DNA (Deoxyribonucleic Acid) and RNA (Ribonucleic Acid).
Structure of Nucleic Acids
Nucleic acids are polymers made of nucleotides. Each nucleotide consists of three components:
a. Nitrogenous Base: Adenine (A), Guanine (G), Cytosine
(C), Thymine (T), or Uracil (U)
b. Pentose Sugar:
Deoxyribose in DNA, Ribose in RNA
c. Phosphate
Group: Links nucleotides together
DNA (Deoxyribonucleic Acid)
DNA is the genetic material found in the nucleus of cells. It carries instructions for making proteins and passing traits from parents to offspring.
Structure: DNA has a double helix structure discovered by Watson and Crick in 1953. Two strands run antiparallel and are held together by hydrogen bonds between complementary bases.
Base Pairing Rules:
· Adenine (A) pairs with Thymine (T)
· Guanine (G) pairs with Cytosine (C)
Example: If one DNA strand has the sequence ATGC, the complementary strand will be TACG.
RNA (Ribonucleic Acid)
RNA is involved in protein synthesis. Unlike DNA, RNA is usually single-stranded and contains uracil instead of thymine.
Types of RNA
|
Type of RNA |
Full Form |
Function |
|
mRNA |
Messenger RNA |
Carries genetic information from DNA to ribosomes |
|
tRNA |
Transfer RNA |
Brings amino acids to ribosomes during protein synthesis |
|
rRNA |
Ribosomal RNA |
Forms the structure of ribosomes |
Differences Between DNA and RNA
|
Feature |
DNA |
RNA |
|
Sugar |
Deoxyribose |
Ribose |
|
Bases |
A, T, G, C |
A, U, G, C |
|
Structure |
Double-stranded helix |
Usually single-stranded |
|
Location |
Nucleus |
Nucleus and cytoplasm |
|
Function |
Stores genetic information |
Involved in protein synthesis |
Functions of Nucleic Acids
a. Storage of Genetic Information: DNA stores all genetic instructions
b. Transmission of Heredity: DNA passes traits from parents to children
c. Protein Synthesis: RNA helps make proteins based on DNA instructions
d. Genetic Variation: Mutations in DNA lead to variation
Example: The color of your eyes, your height, and blood group are all determined by the DNA you inherited from your parents.
Replication of DNA
Before a cell divides, DNA makes a copy of itself. This process is called DNA replication. Each new cell gets an exact copy of genetic material.
Example: When a fertilized egg divides to form an embryo, DNA replication ensures that every cell has the same genetic information.
Mind Map:
Frequently Asked Questions (FAQs)
Q1. What is the difference between saturated and unsaturated fats?
Saturated fats have no double bonds between carbon atoms and are solid at room
temperature (like butter). Unsaturated fats have one or more double bonds and
are liquid at room temperature (like vegetable oil).
Q2. Why are proteins called the workhorses of the cell?
Proteins perform most cellular functions including acting as enzymes, providing
structure, transporting molecules, and defending against diseases. This is why
they are called workhorses.
Q3. What happens when proteins are denatured?
When proteins are denatured, they lose their 3D structure and cannot perform
their biological functions. This can happen due to heat, extreme pH, or
chemicals.
Q4. Which biomolecule stores genetic information?
DNA (Deoxyribonucleic Acid) stores genetic information in all living organisms.
Q5. What is the role of enzymes in our body?
Enzymes act as biological catalysts that speed up chemical reactions in the
body without being consumed. They are essential for digestion, metabolism, and
other life processes.
Q6. How does DNA replication occur?
DNA replication is the process where DNA makes an exact copy of itself before
cell division. The double helix unwinds, and each strand serves as a template
for a new complementary strand.
Q7. What are the main differences between DNA and RNA?
DNA is double-stranded with deoxyribose sugar and thymine base, while RNA is
single-stranded with ribose sugar and uracil base. DNA stores genetic
information; RNA helps in protein synthesis.
Q8. Why are lipids important for cell membranes?
Phospholipids form the lipid bilayer of cell membranes due to their hydrophilic
heads and hydrophobic tails. This structure controls what enters and exits the
cell.
Conclusion
Biomolecules
are the foundation of
life.
Each type plays a unique and essential role:
· Carbohydrates → Provide quick energy
· Lipids → Store energy & protect organs
· Proteins → Build and repair tissues
· Nucleic Acids → Carry genetic code
Excellent! You've now mastered the
fundamental concepts about Biomolecules that are crucial for your competitive
exams.
Regular revision is the key to mastering biology topics. Keep this guide handy
for your quick revisions. Your consistent effort and smart preparation will
definitely lead to success in your exams!
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