Biomolecules Class 11 Question Bank | NCERT Notes, MCQs, Important Questions
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| Biomolecules Class 11 Biology Mind Map with NCERT Notes, Amino Acids, Wet Weight, Dry Weight, and Important CBSE & NEET Concepts. |
- Dr.Sankaykumar Pawar
Biomolecules
1. How do scientists study chemicals present in living tissues?
Text: In higher classes you will learn about how to analyse a living tissue sample and identify a particular organic compound.
Easy Note:
- Scientists study living tissues (leaf, liver, muscle, etc.) to find which chemicals are present.
- These chemicals are called biomolecules.
- In higher studies, you will learn the detailed laboratory methods.
NEET Point: Living tissues contain both organic and inorganic compounds.
2. Extraction of compounds
Text: One extracts the compounds...
Easy Note:
- First, scientists extract (remove) all chemicals from the tissue.
- The extract contains many different compounds mixed together.
Keyword: Extraction = Removing chemicals from a tissue.
3. Separation of compounds
Text: Subjects the extract to various separation techniques...
Easy Note:
- Different laboratory techniques separate one compound from another.
- Each compound is separated step by step.
Examples (Just Know):
- Chromatography
- Centrifugation
NEET Tip: No need to learn techniques in detail from NCERT.
4. Isolation and Purification
Text: One isolates and purifies a compound.
Easy Note:
- Isolation = Obtaining one compound separately.
- Purification = Removing impurities so that only one pure compound remains.
Remember
- Isolation → Separate
- Purification → Make pure
5. Analytical techniques
Text: Analytical techniques give an idea of molecular formula and probable structure.
Easy Note:
- After purification, scientists study the compound.
- They determine:
- Molecular formula
- Chemical structure
Example:
- Glucose → C₆H₁₂O₆
6. What are biomolecules?
Text: All the carbon compounds that we get from living tissues can be called biomolecules.
Easy Note:
- Any carbon-containing compound found in living organisms is called a biomolecule.
Examples
- Carbohydrates
- Proteins
- Lipids
- Nucleic acids
- Vitamins
Definition for NEET:
Biomolecules are carbon-containing compounds present in living organisms.
7. Living organisms also contain inorganic substances
Text: Living organisms have also got inorganic elements and compounds.
Easy Note:
- Living organisms do not contain only biomolecules.
- They also contain:
- Water
- Minerals
- Salts
- Metal ions
Destructive Experiment
8. Wet weight
Text: One weighs a small amount of living tissue...called wet weight.
Easy Note:
- Fresh tissue contains water.
- Weight before drying is called Wet Weight.
Formula
Wet Weight = Dry matter + Water
9. Dry weight
Text: Dry it. All the water evaporates. Remaining material gives dry weight.
Easy Note:
- Heat removes all water.
- Remaining solid is called Dry Weight.
Remember Wet Weight > Dry Weight
10. Burning the tissue
Text: If the tissue is fully burnt...
Easy Note:
- Dry tissue is completely burned.
- Organic compounds burn away.
11. What happens to organic compounds?
Text: Carbon compounds are oxidised into CO₂ and water vapour.
Easy Note:
- Organic compounds contain carbon.
- During burning:
- Carbon → CO₂
- Hydrogen → H₂O vapour
Both escape into the air.
12. What is ash?
Text: What is remaining is called ash.
Easy Note:
- After complete burning, only minerals remain.
- 1 residue is called Ash.
Definition
Ash = Inorganic residue left after complete burning.
13. What does ash contain?
Text: Ash contains inorganic elements like calcium and magnesium.
Easy Note: Ash contains minerals like:
- Calcium (Ca)
- Magnesium (Mg)
- Sodium (Na)
- Potassium (K)
- Iron (Fe)
14. Inorganic compounds
Text: Sulphate, phosphate etc. are seen in acid-soluble fraction.
Easy Note: Living tissues contain inorganic compounds like:
- Sulphate (SO₄²⁻)
- Phosphate (PO₄³⁻)
- Chloride (Cl⁻)
These dissolve in acids.
Elemental Analysis
15. What is elemental analysis?
Text: Elemental analysis gives elemental composition.
Easy Note: It tells us which elements are present.
Examples:
- Carbon
- Hydrogen
- Oxygen
- Nitrogen
- Sulphur
- Phosphorus
It does not tell us the actual compound.
16. Compound analysis
Text: Analysis for compounds gives an idea of organic and inorganic constituents.
Easy Note: Compound analysis identifies:
- Proteins
- Carbohydrates
- Lipids
- DNA
- RNA
It tells which compounds are present.
Table 9.1 – Elements in Earth vs Human Body
| Element | Earth (%) | Human Body (%) | Easy Memory |
|---|---|---|---|
| Oxygen | 46.6 | 65 | Highest in both |
| Carbon | 0.03 | 18.5 | Very high in humans |
| Hydrogen | 0.14 | 9.5 | High in humans due to water |
| Nitrogen | Very little | 3.3 | Needed for proteins |
| Calcium | 3.6 | 1.5 | Bones and teeth |
| Sodium | 2.8 | 0.2 | Nerve function |
| Magnesium | 2.1 | 0.1 | Enzyme activity |
| Sulphur | 0.03 | 0.3 | Amino acids |
| Silicon | 27.7 | Negligible | Mostly in rocks |
NEET Fact
- Silicon is abundant in Earth's crust but almost absent in the human body.
- Carbon is very low in Earth's crust but abundant in living organisms.
Table 9.2 – Important Inorganic Constituents
| Component | Formula | Function |
|---|---|---|
| Sodium | Na⁺ | Nerve impulse |
| Potassium | K⁺ | Muscle contraction |
| Calcium | Ca²⁺ | Bones, blood clotting |
| Magnesium | Mg²⁺ | Enzyme activation |
| Water | H₂O | Universal solvent |
| Sodium chloride | NaCl | Osmotic balance |
| Calcium carbonate | CaCO₃ | Structural material |
| Sulphate | SO₄²⁻ | Mineral ion |
| Phosphate | PO₄³⁻ | ATP, DNA, RNA |
Biological Classification of Organic Compounds
Text: Chemistry identifies aldehydes, ketones... Biology classifies them into amino acids, nucleotide bases, fatty acids.
Easy Note:
Chemistry classification
Based on functional groups:
- Aldehydes
- Ketones
- Alcohols
- Aromatic compounds
Biology classification
Based on biological role:
- Amino acids
- Fatty acids
- Nucleotide bases
- Sugars
NEET Tip: Biology uses biological names rather than chemical functional-group names.
Amino Acids
17. Definition
Text: Amino acids are organic compounds containing amino and acidic group.
Easy Note: Amino acids are the building blocks of proteins.
They contain:
- Amino group (–NH₂)
- Carboxyl group (–COOH)
18. α (Alpha) Amino Acids
Text: Both groups are attached to the same carbon.
Easy Note: In proteins,
- NH₂ and COOH are attached to the same carbon atom.
- This carbon is called the α-carbon.
Hence they are called α-amino acids.
19. Amino acids are substituted methanes
Easy Note: Imagine methane (CH₄).
Replace three H atoms with:
- NH₂
- COOH
- R group
One H remains unchanged.
20. Four groups attached to α-carbon
Every amino acid has four groups attached to the central (α) carbon:
- Hydrogen (H)
- Amino group (–NH₂)
- Carboxyl group (–COOH)
- R group (Variable side chain)
General Formula:
H
|
NH₂ — C — COOH
|
R
21. What is the R group?
Easy Note:
- R group differs in each amino acid.
- It gives each amino acid its unique properties.
Examples:
- Glycine → R = H
- Alanine → R = CH₃
22. Number of amino acids
Text: Those occurring in proteins are only twenty.
Easy Note: Although many amino acids exist, only 20 standard amino acids are used to make proteins in living organisms.
NEET Fact:
- 20 standard amino acids are the building blocks of proteins.
NCERT One-Liners for NEET Revision
- Biomolecules are carbon-containing compounds present in living organisms.
- Extraction removes compounds from tissues.
- Isolation separates one compound.
- Purification removes impurities.
- Wet weight includes water.
- Dry weight is obtained after removing water.
- Ash is the inorganic residue left after burning.
- Organic compounds burn into CO₂ and H₂O.
- Elemental analysis identifies elements.
- Compound analysis identifies biomolecules.
- Oxygen is the most abundant element in the human body.
- Silicon is abundant in Earth's crust but negligible in humans.
- Amino acids are the building blocks of proteins.
- Amino acids contain both amino (–NH₂) and carboxyl (–COOH) groups.
- Protein amino acids are α-amino acids.
- Every amino acid has one variable R group.
- There are 20 standard amino acids found in proteins.
Class 11 Biology (CBSE) – Biomolecules
Question Bank (NCERT Based)
A. Multiple Choice Questions (MCQs)
1. Biomolecules are mainly
a) Carbon compounds present in living organisms b) Minerals only c) Water only d) Inorganic salts
Answer: (a)
2. Wet weight of a tissue includes
a) Minerals only b) Water c) Ash only d) Carbon dioxide
Answer: (b)
3. Dry weight is obtained after
a) Burning tissue b) Removing water c) Adding acids d) Freezing tissue
Answer: (b)
4. Ash obtained after burning tissue mainly contains
a) Proteins b) Lipids c) Inorganic minerals d) Carbohydrates
Answer: (c)
5. Which is an inorganic constituent?
a) Protein b) DNA c) Sodium ion d) Lipid
Answer: (c)
6. Which element is most abundant in the human body?
a) Carbon b) Oxygen c) Nitrogen d) Calcium
Answer: (b)
7. Silicon is abundant in
a) Human body b) Earth's crust c) Proteins d) Blood
Answer: (b)
8. Amino acids are building blocks of
a) Lipids b) Proteins c) DNA d) Vitamins
Answer: (b)
9. Protein amino acids are
a) β-amino acids b) α-amino acids c) γ-amino acids d) δ-amino acids
Answer: (b)
10. Number of standard amino acids in proteins is
a) 10 b) 15 c) 20 d) 25
Answer: (c)
B. Very Short Answer Questions (1 Mark)
1. Define biomolecules.
Answer: Carbon-containing compounds present in living organisms are called biomolecules.
2. What is wet weight?
Answer: Weight of fresh tissue containing water.
3. What is dry weight?
Answer: Weight of tissue after removal of water.
4. What is ash?
Answer: Inorganic residue left after complete burning of tissue.
5. Name two inorganic ions found in living tissues.
Answer: Na⁺ and K⁺.
6. Which element is highest in the human body?
Answer: Oxygen.
7. Name the carbon atom present in amino acids.
Answer: Alpha (α)-carbon.
8. Name the variable group in amino acids.
Answer: R group.
9. How many amino acids are present in proteins?
Answer: 20.
10. Which group makes amino acids acidic?
Answer: Carboxyl group (–COOH).
C. Short Answer Questions (2–3 Marks)
1. Differentiate between wet weight and dry weight.
Answer:
| Wet Weight | Dry Weight |
|---|---|
| Contains water | Water removed |
| Weight of fresh tissue | Weight after drying |
2. What happens when living tissue is completely burnt?
Answer:
- Organic compounds convert into CO₂ and water vapour.
- Inorganic minerals remain as ash.
3. What are biomolecules?
Answer:
- Carbon-containing compounds.
- Present in living organisms.
- Include proteins, carbohydrates, lipids and nucleic acids.
4. Write four groups attached to α-carbon.
Answer:
- Hydrogen
- Amino group
- Carboxyl group
- R group
5. Name four inorganic constituents.
Answer:
- Water
- Sodium
- Potassium
- Calcium
D. Long Answer Questions (5 Marks)
1. Describe how scientists analyse living tissues.
Answer:
- Living tissue is collected.
- Compounds are extracted.
- Different compounds are separated.
- Pure compound is isolated.
- Analytical techniques determine molecular formula and structure.
- Carbon compounds are called biomolecules.
2. Explain the destructive experiment performed on living tissues.
Answer:
- Fresh tissue is weighed (wet weight).
- Tissue is dried to obtain dry weight.
- Dry tissue is completely burnt.
- Organic compounds become CO₂ and water vapour.
- Remaining ash contains inorganic minerals.
- This proves that living tissues contain both organic and inorganic substances.
3. Explain the structure of amino acids.
Answer:
- Amino acids contain amino (–NH₂) and carboxyl (–COOH) groups.
- Both are attached to the same α-carbon.
- α-carbon also carries hydrogen and R group.
- R group differs in each amino acid.
- Twenty amino acids form proteins.
E. Fill in the Blanks
-
Carbon compounds present in living organisms are called Biomolecules.
-
Fresh tissue gives Wet weight.
-
After drying tissue we obtain Dry weight.
-
Complete burning leaves Ash.
-
Ash mainly contains Inorganic minerals.
-
Amino acids contain Amino and Carboxyl groups.
-
Variable side chain is called R group.
-
Protein amino acids are α-amino acids.
-
Human body contains highest amount of Oxygen.
-
Proteins are made up of 20 amino acids.
F. Assertion and Reason
1.
Assertion (A): Ash contains inorganic minerals.
Reason (R): Organic compounds burn into CO₂ and water.
Answer: Both A and R are true and R is the correct explanation.
2.
Assertion: Wet weight is greater than dry weight.
Reason: Fresh tissue contains water.
Answer: Both true and Reason correctly explains Assertion.
3.
Assertion: Protein amino acids are α-amino acids.
Reason: Both amino and carboxyl groups are attached to the same carbon atom.
Answer: Both true and Reason is correct explanation.
4.
Assertion: Silicon is abundant in human body.
Reason: Silicon is abundant in Earth's crust.
Answer: Assertion is false, Reason is true.
5.
Assertion: Biomolecules contain carbon.
Reason: All carbon compounds are biomolecules.
Answer: Assertion is true, Reason is false.
G. Match the Columns
| Column A | Column B |
|---|---|
| Wet weight | Fresh tissue |
| Dry weight | Water removed |
| Ash | Inorganic residue |
| Amino acid | Protein building block |
| Oxygen | Highest in human body |
Answers
Wet weight → Fresh tissue
Dry weight → Water removed
Ash → Inorganic residue
Amino acid → Protein building block
Oxygen → Highest in human body
H. Statement-Based Questions
Statement I
Biomolecules are carbon-containing compounds.
Statement II
Living organisms contain inorganic minerals also.
Choose the correct option.
a) Both true
b) Both false
c) I true II false
d) I false II true
Answer: (a)
Statement I
Twenty amino acids form proteins.
Statement II
All amino acids have the same R group.
Answer: Statement I true, Statement II false.
I. Case Study Questions
Case Study
A scientist collected a fresh leaf. He measured its weight, dried it completely, and measured it again. Then he burnt the dried leaf. Only a small amount of ash remained.
Questions
1. What is the first weight called?
Answer: Wet weight.
2. What is the second weight called?
Answer: Dry weight.
3. What does ash contain?
Answer: Inorganic minerals.
4. Why did the weight decrease after drying?
Answer: Water evaporated.
5. Why did only ash remain after burning?
Answer: Organic compounds burnt into CO₂ and water vapour.
J. Important One-Word Questions
- Building blocks of proteins → Amino acids
- Residue after burning → Ash
- Fresh tissue weight → Wet weight
- Weight after drying → Dry weight
- Variable group of amino acid → R group
- Most abundant element in human body → Oxygen
- Number of standard amino acids → 20
- Carbon compounds of living organisms → Biomolecules
CBSE Exam Tip (NCERT-Based)
Focus especially on these frequently tested topics:
- Definition of biomolecules
- Wet weight vs dry weight
- Ash and destructive experiment
- Organic vs inorganic constituents
- Elemental analysis vs compound analysis
- Structure of α-amino acids
- Four groups attached to the α-carbon
- The 20 standard amino acids
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