NCERT Notes for Class 11 Biology Chapter 9 Biomolecules- Download PDF Notes

NCERT Notes for Class 11 Biology Chapter 9 Biomolecules: Biology is the study of life, and at the core of it, biomolecules play a significant part in maintaining life processes. This chapter of NCERT explores the structure, function, and importance of these vital organic molecules that serve as the building units of life.

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This Story also Contains

1. What Are Biomolecules?
2. Types of Biomolecules
3. Most Important Questions Class 11 Biology Chapter 9
4. Approach to Solve Questions of Class 11 Biology Chapter 9
5. Chapter-Wise NCERT Class 11 Notes Biology

From the food we consume to the DNA with our genetic information, biomolecules play a role in all aspects of life. Biomolecules are engaged in crucial processes such as energy generation, growth, repair, and metabolism. Students who wish to perform well in biology and competitive examinations like NEET can have a clear understanding from these NCERT Notes for Class 11.

These NCERT Class 11 Biology Notes discuss carbohydrates, proteins, lipids, nucleic acids, and enzymes, their structure, types, and biological significance. Let us learn the major concepts of this chapter step by step.

Also, students can refer to:

• NCERT Solutions for Class 11 Biology Chapter 9 Biomolecules
• NCERT Exemplar for Class 11 Biology Chapter 9 Biomolecules

What Are Biomolecules?

Biomolecules are organic molecules essential for the structure and function of living organisms. These molecules are primarily composed of carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur. Biomolecules are involved in various biological processes, such as energy production, growth, metabolism, and genetic information transfer.

Definition and Importance of Biomolecules

Biomolecules are chemical compounds present in living organisms that contribute to cellular functions and life-sustaining processes. Their importance includes:

• Providing Energy: Carbohydrates and lipids serve as energy sources.

• Structural Components: Proteins and lipids contribute to cell membranes and tissues.

• Genetic Information: Nucleic acids (DNA & RNA) store and transmit genetic instructions.

• Catalysis of Reactions: Enzymes (proteins) speed up biochemical reactions.

• Cell Communication: Hormones and neurotransmitters regulate body functions.

Classification of Biomolecules

Biomolecules are categorised into two major types:

1. Organic Biomolecules: Contain carbon and hydrogen and form the backbone of life. Examples include carbohydrates, proteins, lipids, and nucleic acids.

2. Inorganic Biomolecules: Do not contain carbon-hydrogen bonds and are essential for biological functions. Examples include water, minerals, and gases like oxygen and carbon dioxide.

Subject-Wise NCERT Exemplar Solutions

• NCERT Exemplar Class 11 Solutions
• NCERT Exemplar Class 11 Maths
• NCERT Exemplar Class 11 Physics
• NCERT Exemplar Class 11 Chemistry
• NCERT Exemplar Class 11 Biology

Types of Biomolecules

The different types of biomolecules are described as follows:

1. Carbohydrates

Carbohydrates are organic compounds composed of carbon (C), hydrogen (H), and oxygen (O) in a ratio of 1:2:1. Their general formula is (CH₂O)ₙ.

Classification of Carbohydrates

Carbohydrates are categorised based on their complexity:

• Monosaccharides (Simple Sugars): The smallest carbohydrate units, e.g., glucose, fructose, galactose.

• Disaccharides: Formed by the condensation of two monosaccharides, e.g., sucrose (glucose + fructose), lactose (glucose + galactose).

• Polysaccharides: Long chains of monosaccharides, e.g., starch (plant storage), glycogen (animal storage), and cellulose (plant cell walls).

Functions of Carbohydrates

• Provide immediate energy through glucose metabolism.

• Act as structural components (e.g., cellulose in plants, chitin in fungi).

• Play a role in cell recognition and signalling (glycoproteins).

2. Proteins

Proteins are macromolecules composed of amino acids linked by peptide bonds. Each amino acid contains an amino group (-NH₂), a carboxyl group (-COOH), and a variable side chain (R-group).

Classification of Proteins

Proteins are classified based on their structure and function:

• Structural Proteins: Provide support, e.g., collagen in connective tissues.

• Functional Proteins: Enzymes, hormones, and antibodies perform specific biological functions.

• Fibrous Proteins: Insoluble, providing structural support, e.g., keratin in hair.

• Globular Proteins: Soluble, involved in metabolism, e.g., haemoglobin.

Functions of Proteins

• Catalyses biochemical reactions (enzymes).

• Provide structural support (collagen, keratin).

• Transport molecules (haemoglobin carries oxygen).

• Regulate body functions (hormones like insulin).

• Defend against infections (antibodies in immunity).

3. Lipids

Lipids are hydrophobic molecules composed mainly of carbon, hydrogen, and oxygen. They are insoluble in water but soluble in organic solvents like ethanol.

Classification of Lipids

• Simple Lipids: Fats and oils (triglycerides) are composed of glycerol and fatty acids.

• Compound Lipids: Contain additional groups, e.g., phospholipids in cell membranes.

• Derived Lipids: Steroids (cholesterol), terpenes, and fat-soluble vitamins.

Functions of Lipids

• Store energy for long-term use.

• Act as structural components of cell membranes (phospholipids).

• Serve as insulation and protection (fat in the body).

• Function as signaling molecules (steroids like hormones).

4. Nucleic Acids

Nucleic acids are polymers of nucleotides, where each nucleotide consists of:

• A pentose sugar (ribose in RNA, deoxyribose in DNA).

• A phosphate group.

• A nitrogenous base (adenine, guanine, cytosine, thymine in DNA, uracil in RNA).

Types of Nucleic Acids

Nucleic acids are classified as:

1. DNA (Deoxyribonucleic Acid):

• Double-stranded helix.

• Stores genetic information.

• Composed of adenine (A), thymine (T), cytosine (C), and guanine (G).

2. RNA (Ribonucleic Acid):

• Single-stranded.

• Involved in protein synthesis.

• Contains uracil (U) instead of thymine.

Functions of Nucleic Acids

• DNA stores and transmits genetic information.

• RNA helps in protein synthesis by translating genetic codes into proteins.

• Regulates gene expression and cellular activities.

Also Read:

• NCERT Books for Class 11
• NCERT Syllabus for Class 11

Most Important Questions Class 11 Biology Chapter 9

Biomolecules are organic compounds essential for the structure and function of living organisms. They include carbohydrates, proteins, lipids, and nucleic acids, each playing unique roles in metabolism, energy storage, genetic information, and cellular structure.

Q1. Which is the most abundant chemical found in living organisms?
A. Hydrogen
B. Oxygen
C. Water
D. Carbon

Answer:
Water is the most abundant chemical in living organisms, making up a major portion of their composition.
Hence, the correct option is C. Water.

Q2. How many major classes of biomolecules are present in living organisms?
A. Two
B. Three
C. Four
D. Five

Answer:
There are four major classes of biomolecules: carbohydrates, proteins, lipids, and nucleic acids.
Hence, the correct option is C. Four.

Q3. What are the products formed after hydrolysis of lactose?
A. Glucose and fructose
B. Glucose and galactose
C. Glucose and sucrose
D. Glucose and maltose

Answer:
Lactose breaks down into glucose and galactose upon hydrolysis.
Hence, the correct option is B. Glucose and galactose.

Q4. What is the monomeric unit of nucleic acids?
A. Amino acid
B. Fatty acid
C. Nucleotide
D. Monosaccharide

Answer:
Nucleotides are the monomeric units that make up nucleic acids.
Hence, the correct option is C. Nucleotide.

Q5. Which polymer forms the exoskeleton of insects?
A. Cellulose
B. Glycogen
C. Chitin
D. Starch

Answer:
Chitin forms the exoskeleton of insects.
Hence, the correct option is C. Chitin.

Subject-Wise NCERT Solutions

• NCERT Solutions for Class 11 Mathematics
• NCERT Solutions for Class 11 Chemistry
• NCERT Solutions for Class 11 Physics

• NCERT Solutions for Class 11 Biology

Approach to Solve Questions of Class 11 Biology Chapter 9

To answer Biomolecules questions well, adopt this easy-to-follow approach:

1. Read and learn the rudimentary definitions and classes of biomolecules- carbohydrates, proteins, lipids, and nucleic acids- including their forms and functions.
2. Master core vocabulary such as monomer, polymer, enzyme, metabolite, and provide examples for each.
3. Practice structurally drawing drawings of major biomolecules and learning types of bonds, including glycosidic, peptide, ester, and phosphodiester bonds.
4. Study enzyme properties: their structure, their functioning, and which factors influence their activity (such as temperature, pH, and inhibitors).
5. Regularly solve NCERT textbook questions and previous years' questions to acclimate yourself with the question pattern and strengthen your grip

Chapter-Wise NCERT Class 11 Notes Biology

The various notes for chapters from Class 11 are mentioned below: