Every living cell works through chemicals, but not all chemicals have the same role. Biomolecules are chemical compounds found in living organisms and required for cellular structure and function. Proteins, carbohydrates, lipids, nucleic acids, enzymes, and metabolites are major examples of biomolecules.
Biomolecules explain why carbon, hydrogen, oxygen, nitrogen, proteins, nucleic acids, polysaccharides, and enzymes matter in life processes. CBSE 2026 questions from this chapter usually test definitions, chemical analysis, metabolites, macromolecules, protein structure, enzyme activity, and cofactors. These Important Questions Class 11 Biology Chapter 9 are based on NCERT Reprint 2026-27 and written for clear board-style revision.
Key Takeaways
- Water: It forms 70 to 90 per cent of total cellular mass.
- Proteins: They are heteropolymers made of amino acids linked by peptide bonds.
- Lipids: They are not true macromolecules but appear in the acid-insoluble fraction.
- Enzymes: They lower activation energy and increase reaction rate.
Important Questions Class 11 Biology Chapter 9 Structure 2026
| Principle |
Application |
Unit |
| Chemical analysis |
Separates acid-soluble and acid-insoluble fractions |
Dalton |
| Biomacromolecules |
Builds proteins, nucleic acids, and polysaccharides |
Polymer |
| Enzyme action |
Converts substrate into product through active site |
Reaction rate |
Biomolecules Class 11 Important Questions with Answers
Biomolecules class 11 important questions usually begin with definitions and examples. Students should connect each term with its role inside living tissues.
Q1. What are biomolecules?
Answer: Biomolecules are carbon-containing compounds found in living organisms.
They include amino acids, sugars, fatty acids, nucleotides, proteins, polysaccharides, and nucleic acids.
Example: DNA, RNA, proteins, starch, glycogen, and enzymes are biomolecules.
Q2. Why are carbon and hydrogen more abundant in living tissues?
Answer: Carbon and hydrogen are more abundant because living tissues contain many organic compounds.
Organic compounds like carbohydrates, proteins, lipids, and nucleic acids are built mainly around carbon skeletons.
Example: Glucose contains carbon, hydrogen, and oxygen.
Q3. What is the difference between wet weight and dry weight?
Answer: Wet weight is the weight of living tissue before water removal.
Dry weight is the weight left after all water evaporates from the tissue.
Final Result: Dry weight helps measure non-water chemical material in living tissue.
Q4. What is ash in chemical analysis of living tissue?
Answer: Ash is the inorganic residue left after complete burning of dried tissue.
Carbon compounds oxidise into gases like carbon dioxide and water vapour.
Example: Ash may contain calcium, magnesium, sulphate, and phosphate.
Q5. What are amino acids?
Answer: Amino acids are organic compounds with amino and carboxyl groups on the same alpha carbon.
They also contain hydrogen and a variable R group.
Example: Glycine, alanine, serine, lysine, and glutamic acid are amino acids.
Biomolecules Class 11 MCQ with Answers
Biomolecules class 11 MCQ questions test definitions, examples, and NCERT facts. Read every option carefully because many terms look similar.
Q1. The most abundant chemical in living organisms is:
(A) Protein
(B) Water
(C) Lipid
(D) Nucleic acid
Answer: (B) Water
Water forms 70 to 90 per cent of total cellular mass.
Q2. Proteins are polymers of:
(A) Nucleotides
(B) Fatty acids
(C) Amino acids
(D) Glucose
Answer: (C) Amino acids
Proteins are polypeptides made of amino acids linked by peptide bonds.
Q3. DNA and RNA are made of:
(A) Amino acids
(B) Nucleotides
(C) Fatty acids
(D) Minerals
Answer: (B) Nucleotides
Nucleic acids are polynucleotides.
Q4. The most abundant protein in the animal world is:
(A) Insulin
(B) Collagen
(C) Trypsin
(D) Antibody
Answer: (B) Collagen
Collagen forms intercellular ground substance in animals.
Q5. The most abundant protein in the biosphere is:
(A) RuBisCO
(B) Insulin
(C) Haemoglobin
(D) Keratin
Answer: (A) RuBisCO
RuBisCO is Ribulose bisphosphate Carboxylase-Oxygenase.
Q6. Cellulose is a polymer of:
(A) Fructose
(B) Glucose
(C) Amino acids
(D) Nucleotides
Answer: (B) Glucose
Cellulose is a homopolymer made only of glucose units.
Q7. The active site is found in:
(A) Substrate
(B) Enzyme
(C) Product
(D) Cofactor only
Answer: (B) Enzyme
The active site is the pocket where the substrate fits.
Q8. Lipids are generally:
(A) Water soluble
(B) Water insoluble
(C) Made of nucleotides
(D) Made of amino acids only
Answer: (B) Water insoluble
Lipids do not dissolve in water due to their non-polar nature.
Q9. Competitive inhibition occurs when inhibitor resembles:
(A) Product
(B) Substrate
(C) Cofactor
(D) Apoenzyme
Answer: (B) Substrate
The inhibitor competes with the substrate for the active site.
Q10. Enzymes usually work best at:
(A) Any pH
(B) Any temperature
(C) Optimum pH and temperature
(D) Only freezing temperature
Answer: (C) Optimum pH and temperature
Each enzyme has a specific optimum pH and temperature.
How to Analyse Chemical Composition Class 11 Questions
How to analyse chemical composition class 11 questions focus on tissue grinding, filtration, and fractions. The main idea is to separate small soluble compounds from larger insoluble compounds.
Q1. How is chemical composition of living tissue analysed?
Answer: Living tissue is ground in trichloroacetic acid and filtered.
- Tissue Used: A vegetable, liver piece, or microbial paste can be used.
- Chemical Used: Trichloroacetic acid helps extract chemical compounds.
- Separation Step: Filtration separates the filtrate and retentate.
- Final Result: The filtrate forms the acid-soluble pool.
Q2. What is the acid-soluble pool?
Answer: The acid-soluble pool is the filtrate obtained after tissue extraction.
It contains small molecular weight compounds found in living tissues.
Example: Amino acids, sugars, nucleotides, and fatty acids occur in this fraction.
Q3. What is the acid-insoluble fraction?
Answer: The acid-insoluble fraction is the retentate left after filtration.
It mainly contains proteins, nucleic acids, polysaccharides, and membrane fragments.
Final Result: This fraction represents the macromolecular part of living tissue.
Q4. Why is elemental analysis important in biomolecules?
Answer: Elemental analysis shows which elements are present in living tissue.
It helps compare living matter with non-living matter.
Example: Living tissues contain more carbon and hydrogen relative to earth’s crust.
Q5. What does compound analysis show?
Answer: Compound analysis shows the types of organic and inorganic substances present.
It identifies groups like amino acids, sugars, fatty acids, and nucleotides.
Final Result: It explains the chemical nature of living tissues.
Primary and Secondary Metabolites Class 11 Questions
Primary and secondary metabolites class 11 questions test examples and functions. Primary metabolites support normal physiology, while secondary metabolites often support ecological or human-use roles.
Q1. What are primary metabolites?
Answer: Primary metabolites are biomolecules with known roles in normal physiological processes.
They occur in animal, plant, fungal, and microbial cells.
Example: Amino acids, sugars, nucleotides, and fatty acids are primary metabolites.
Q2. What are secondary metabolites?
Answer: Secondary metabolites are compounds mainly found in plants, fungi, and microbes.
Their functions in host organisms are not always fully understood.
Example: Alkaloids, flavonoids, rubber, essential oils, antibiotics, and pigments are secondary metabolites.
Q3. Give examples of secondary metabolites useful to humans.
Answer: Rubber, drugs, spices, scents, gums, and pigments are useful secondary metabolites.
They support industries, medicine, food, and agriculture.
Example: Morphine, codeine, vinblastin, curcumin, and essential oils are secondary metabolites.
Q4. What is the difference between primary and secondary metabolites?
Answer: Primary metabolites support basic life processes, while secondary metabolites often have specialised roles.
Primary metabolites include amino acids and sugars.
Secondary metabolites include alkaloids, toxins, and essential oils.
Biomacromolecules Class 11 Notes and Questions
Biomacromolecules class 11 notes should focus on molecular weight and polymeric nature. Proteins, nucleic acids, and polysaccharides are true macromolecules.
Q1. What are biomacromolecules?
Answer: Biomacromolecules are large biomolecules with molecular weight above about 10,000 daltons.
They occur mainly in the acid-insoluble fraction.
Example: Proteins, nucleic acids, and polysaccharides are biomacromolecules.
Q2. Why are lipids not true macromolecules?
Answer: Lipids are not true macromolecules because their molecular weight usually stays below 800 daltons.
They appear in the acid-insoluble fraction due to membrane association.
Final Result: Lipids are small molecules present in larger membrane structures.
Q3. What is the difference between micromolecules and macromolecules?
Answer: Micromolecules have molecular weight below 1000 daltons.
Macromolecules have molecular weight around 10,000 daltons or more.
Example: Amino acids are micromolecules, while proteins are macromolecules.
Q4. Why are proteins, nucleic acids, and polysaccharides called polymers?
Answer: They are called polymers because they contain repeating building blocks.
Proteins contain amino acids, nucleic acids contain nucleotides, and polysaccharides contain sugars.
Final Result: Their monomers join to form long biological chains.
Proteins Class 11 Biology Questions with Answers
Proteins class 11 biology questions often ask about amino acids, peptide bonds, and structural levels. Students should remember proteins as heteropolymers.
Q1. What are proteins?
Answer: Proteins are polypeptides made of amino acids linked by peptide bonds.
Each protein has a specific amino acid sequence.
Example: Collagen, insulin, trypsin, antibodies, and receptors are proteins.
Q2. Why are proteins called heteropolymers?
Answer: Proteins are heteropolymers because they contain different types of amino acids.
A homopolymer has only one repeating monomer.
Example: A protein may contain alanine, lysine, serine, glycine, and tryptophan.
Q3. What is a peptide bond?
Answer: A peptide bond joins two amino acids in a protein chain.
It forms between the amino group of one amino acid and carboxyl group of another.
Final Result: Peptide bonds build polypeptide chains.
Q4. What are essential amino acids?
Answer: Essential amino acids are amino acids that the body cannot synthesise.
They must come from food.
Example: Dietary proteins supply essential amino acids.
Q5. What are the functions of proteins?
Answer: Proteins perform structural, enzymatic, hormonal, transport, and defence functions.
- Collagen: It forms intercellular ground substance.
- Trypsin: It acts as an enzyme.
- Insulin: It acts as a hormone.
- Antibodies: They fight infectious agents.
- GLUT-4: It helps glucose enter cells.
Protein Structure Class 11 Biology Questions with Answers
Protein structure class 11 biology questions test four levels of organisation. Explain each level with a direct role and example.
Q1. What is primary structure of protein?
Answer: Primary structure is the linear sequence of amino acids in a protein.
It tells which amino acid comes first, second, and later.
Final Result: The first amino acid is N-terminal, and the last is C-terminal.
Q2. What is secondary structure of protein?
Answer: Secondary structure is local folding of the protein chain.
Some parts form a helix, while other parts fold into sheet-like forms.
Example: Proteins usually show right-handed helices.
Q3. What is tertiary structure of protein?
Answer: Tertiary structure is the three-dimensional folding of a protein chain.
It gives the protein its active shape.
Final Result: Tertiary structure is necessary for many biological functions.
Q4. What is quaternary structure of protein?
Answer: Quaternary structure is the arrangement of more than one polypeptide subunit.
It occurs in proteins made of multiple chains.
Example: Adult human haemoglobin has two alpha and two beta subunits.
Polysaccharides Class 11 Biology Questions with Answers
Polysaccharides class 11 biology questions focus on glucose polymers and storage forms. Cellulose, starch, and glycogen are the most important examples.
Q1. What are polysaccharides?
Answer: Polysaccharides are long chains of monosaccharides.
They are carbohydrates found in the acid-insoluble fraction.
Example: Cellulose, starch, glycogen, and inulin are polysaccharides.
Q2. Why is cellulose called a homopolymer?
Answer: Cellulose is called a homopolymer because it contains only glucose units.
It forms the structural material of plant cell walls.
Final Result: Paper and cotton fibre are mainly cellulosic.
Q3. What is glycogen?
Answer: Glycogen is the storage polysaccharide found in animals.
It is a branched polymer of glucose.
Final Result: It stores energy in animal tissues.
Q4. How is starch different from cellulose?
Answer: Starch forms helical secondary structures, while cellulose does not form complex helices.
Starch can hold iodine molecules and gives blue colour.
Final Result: Cellulose does not give the same iodine colour response.
Q5. What is chitin?
Answer: Chitin is a complex polysaccharide found in arthropod exoskeletons.
It contains chemically modified sugar units.
Example: Insects and crustaceans have chitin in their outer covering.
Nucleic Acids Class 11 Biology Questions with Answers
Nucleic acids class 11 biology questions test nucleotide structure and DNA-RNA differences. Nucleic acids are polynucleotides.
Q1. What are nucleic acids?
Answer: Nucleic acids are polynucleotides found in living cells.
They store and transmit genetic information.
Example: DNA and RNA are nucleic acids.
Q2. What are the components of a nucleotide?
Answer: A nucleotide has nitrogenous base, pentose sugar, and phosphate group.
- Base: It may be adenine, guanine, cytosine, thymine, or uracil.
- Sugar: It may be ribose or deoxyribose.
- Phosphate: It links nucleotides in nucleic acid chains.
- Final Result: Nucleotides form DNA and RNA.
Q3. What is the difference between a nucleoside and nucleotide?
Answer: A nucleoside contains a nitrogenous base and sugar.
A nucleotide contains a nitrogenous base, sugar, and phosphate.
Example: Adenosine is a nucleoside, while adenylic acid is a nucleotide.
Q4. What is the difference between DNA and RNA?
Answer: DNA contains deoxyribose sugar, while RNA contains ribose sugar.
DNA usually stores hereditary information.
RNA helps in gene expression and protein synthesis.
Q5. Name the purines and pyrimidines found in nucleic acids.
Answer: Adenine and guanine are purines.
Cytosine, thymine, and uracil are pyrimidines.
Final Result: DNA has thymine, while RNA has uracil.
Enzymes Class 11 Important Questions with Answers
Enzymes class 11 important questions are high-value for CBSE 2026. Focus on active site, substrate specificity, activation energy, and factors affecting activity.
Q1. What are enzymes?
Answer: Enzymes are biological catalysts that increase the rate of biochemical reactions.
Almost all enzymes are proteins, but some nucleic acids act as ribozymes.
Example: Carbonic anhydrase, trypsin, catalase, and peroxidase are enzymes.
Q2. What is the active site of an enzyme?
Answer: The active site is a pocket in the enzyme where the substrate binds.
It gives the enzyme its substrate specificity.
Final Result: The active site helps form the enzyme-substrate complex.
Q3. How do enzymes lower activation energy?
Answer: Enzymes lower the energy barrier needed to convert substrate into product.
- Substrate Binding: The substrate binds to the active site.
- Transition State: The substrate reaches a less stable transition state.
- Energy Change: The enzyme lowers the required activation energy.
- Final Result: The product forms faster than in an uncatalysed reaction.
Q4. Explain enzyme action through ES complex.
Answer: Enzyme action begins when substrate binds to the active site.
- E + S: Enzyme and substrate come together.
- ES Complex: The substrate fits into the active site.
- EP Complex: Bonds break or form inside the active site.
- E + P: Product leaves, and enzyme becomes free again.
Q5. Why is carbonic anhydrase a strong example of enzyme action?
Answer: Carbonic anhydrase greatly increases the formation of carbonic acid.
Without enzyme, about 200 molecules form in one hour.
With enzyme, about 600,000 molecules form every second.
Final Result: It increases reaction rate by about 10 million times.
Q6. What factors affect enzyme activity class 11?
Answer: Temperature, pH, substrate concentration, and inhibitors affect enzyme activity.
Each enzyme works best at optimum temperature and optimum pH.
Example: High temperature denatures many protein enzymes.
Q7. What is competitive inhibition?
Answer: Competitive inhibition occurs when an inhibitor resembles the substrate.
The inhibitor competes for the active site.
Example: Malonate inhibits succinic dehydrogenase because it resembles succinate.
Q8. What are cofactors in enzymes class 11?
Answer: Cofactors are non-protein parts required for enzyme activity.
They help the apoenzyme become catalytically active.
Types: Prosthetic groups, coenzymes, and metal ions are cofactors.
Q9. What is the difference between apoenzyme and cofactor?
Answer: Apoenzyme is the protein part of an enzyme.
Cofactor is the non-protein part required for catalytic activity.
Final Result: Enzyme activity may stop when the cofactor is removed.
Q10. What are the six classes of enzymes?
Answer: Enzymes are classified by the reactions they catalyse.
- Oxidoreductases: They catalyse oxidation-reduction reactions.
- Transferases: They transfer groups between substrates.
- Hydrolases: They catalyse hydrolysis reactions.
- Lyases: They remove groups without hydrolysis.
- Isomerases: They convert one isomer into another.
- Ligases: They join two compounds using energy.
Class 11 Biology Chapter 9 Questions and Answers
Class 11 biology chapter 9 questions and answers should cover definitions, differences, examples, and application-based enzyme questions. These answers follow the NCERT Reprint 2026-27 scope.
Q1. Why are amino acids called substituted methanes?
Answer: Amino acids are called substituted methanes because four groups attach to the alpha carbon.
These groups are hydrogen, amino group, carboxyl group, and R group.
Final Result: The R group decides the type of amino acid.
Q2. What is zwitterionic form of amino acid?
Answer: Zwitterionic form has both positive and negative charges in the same molecule.
Amino and carboxyl groups ionise at different pH values.
Final Result: Amino acid structure changes with pH.
Q3. What are phospholipids?
Answer: Phospholipids are lipids containing phosphorus and a phosphorylated organic compound.
They are important components of cell membranes.
Example: Lecithin is a phospholipid.
Q4. Why are biomolecules classified biologically, not only chemically?
Answer: Biological classification explains their role in living systems.
Chemistry identifies groups like aldehydes and ketones.
Biology groups them as amino acids, sugars, fatty acids, and nucleotides.
Q5. Why is water the most abundant chemical in living organisms?
Answer: Water forms the main medium for biochemical reactions.
It supports transport, temperature control, and cellular metabolism.
Final Result: Living cells contain about 70 to 90 per cent water.
Q6. What is the role of GLUT-4 protein?
Answer: GLUT-4 enables glucose transport into cells.
It helps move glucose across the cell membrane.
Final Result: It supports cellular glucose uptake.
Q7. Why are enzymes damaged at high temperature?
Answer: High temperature denatures enzyme proteins.
Denaturation changes the tertiary structure and active site.
Final Result: The substrate can no longer fit properly.
Q8. What is a metabolic pathway?
Answer: A metabolic pathway is a sequence of enzyme-catalysed reactions.
Each step converts one compound into another.
Example: Glucose converts into pyruvic acid through ten enzyme-catalysed steps.
Q9. What are ribozymes?
Answer: Ribozymes are nucleic acids with catalytic activity.
They behave like enzymes but are not proteins.
Final Result: Not all enzymes are proteinaceous.
Q10. Why is tertiary structure important in proteins?
Answer: Tertiary structure gives proteins their functional three-dimensional shape.
Many active sites and binding regions form only after proper folding.
Final Result: Protein function depends strongly on tertiary structure.