Chapter 2: Biological Molecules Exercise Solution Class 11

MCQs with answers from Chapter 2 Biological Molecules (Federal Board, 11th Class):

Biological Molecules MCQs Solution of Chapter 2

1. An amino acid molecule has the following structure: Which two groups combine to form a peptide link between two amino acids?

(A) 1 and 2
(B) 1 and 3
(C) 2 and 3
(D) 2 and 4
✅ Answer: (C) 2 and 3

2. Which class of molecule is the major component of the cell membrane?

(A) Phospholipid
(B) Cellulose
(C) Wax
(D) Triglyceride
✅ Answer: (A) Phospholipid

3. Glycerol is the backbone molecule for:

(A) ATP
(B) Terpenes
(C) Neutral lipids
(D) Steroids
✅ Answer: (C) Neutral lipids

4. A fatty acid is unsaturated if it:

(A) Contains hydrogen
(B) Contains double bonds
(C) Contains an acid group
(D) All of them
✅ Answer: (B) Contains double bonds

5. In RNA, the nitrogen base that takes the place of thymine is:

(A) Adenine
(B) Cytosine
(C) Guanine
(D) Uracil
✅ Answer: (D) Uracil

6. The ending "-ose" means a substance is a:

(A) Sugar
(B) Lipid
(C) Protein
(D) Nucleic acid
✅ Answer: (A) Sugar

7. Glycolipids and lipoproteins are important components of:

(A) Cellular membrane
(B) Cell wall
(C) Both of them
(D) None of them
✅ Answer: (A) Cellular membrane

8. When two amino acids are linked to form a peptide bond, what is removed?

(A) Hydroxyl (-OH)
(B) Water (H₂O)
(C) Carbon (C)
(D) Nitrogen (N)
✅ Answer: (B) Water (H₂O)

9. What is the theoretical number of chemically different dipeptides that may be assembled from two amino acids?

(A) One
(B) Two
(C) Three
(D) Four
✅ Answer: (D) Four

10. A polar molecule is ________ in water.

(A) Soluble
(B) Insoluble
(C) Reactive
(D) Inert
✅ Answer: (A) Soluble

11. Which statement correctly describes a property of water?

(A) A relatively large amount of heat is needed to increase its temperature.
(B) At normal room temperature, its molecules are bound together by ionic bonds.
(C) The highest density of water occurs below its freezing point.
(D) Water acts as a solvent for non-polar molecules.
✅ Answer: (A) A relatively large amount of heat is needed to increase its temperature.

12. Estrogen, Vitamin-D, and cholesterol are all examples of:

(A) Glycolipids
(B) Lipoproteins
(C) Terpenes
(D) Steroids
✅ Answer: (D) Steroids

13. Which term includes all others?

(A) Carbohydrate
(B) Starch
(C) Monosaccharide
(D) Polysaccharide
✅ Answer: (A) Carbohydrate

14. Choose the pair of terms that correctly completes this sentence: Nucleotides are to nucleic acids as ________ are to proteins.

(A) Nucleic acids; Amino acids
(B) Amino acids; Polypeptides
(C) Glycosidic linkages; Polypeptide linkages
(D) Polymers; Polypeptides
✅ Answer: (B) Amino acids; Polypeptides

15. The enantiomer of D-glucose is:

(A) D-galactose
(B) L-galactose
(C) Both of them
(D) None of them
✅ Answer: (D) None of them

Biological Molecules Short Questions with answers from Chapter 2 (Federal Board, 11th Class):

2️⃣ How would you describe biochemistry?

✅ Answer: Biochemistry is the branch of science that studies the chemical composition and reactions of biomolecules in living organisms. It includes the study of proteins, carbohydrates, lipids, nucleic acids, and the processes like metabolism, enzyme activity, and genetic regulation.

3️⃣ What are bioelements?

✅ Answer: Bioelements are chemical elements essential for the structure and function of living organisms. They are categorized into:
✔ Major bioelements (99%) – Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N), Phosphorus (P), Sulfur (S).
✔ Minor bioelements (<1%) – Calcium (Ca), Potassium (K), Sodium (Na), Chlorine (Cl), Magnesium (Mg).
✔ Trace elements (<0.01%) – Iron (Fe), Copper (Cu), Zinc (Zn), Manganese (Mn), Iodine (I).

4️⃣ Describe the chemical composition of protoplasm.

✅ Answer: Protoplasm is the living content of a cell, composed of:
✔ Water (70-80%) – Acts as a solvent & medium for biochemical reactions.
✔ Proteins (15-18%) – Structural & enzymatic functions.
✔ Carbohydrates (3-4%) – Energy source.
✔ Lipids (2-3%) – Energy storage, membrane structure.
✔ Nucleic Acids (DNA & RNA) – Genetic information & protein synthesis.
✔ Inorganic Ions (Na⁺, K⁺, Cl⁻, Mg²⁺, Ca²⁺) – Maintain cellular function.

5️⃣ What are the four fundamental kinds of biological molecules? Explain.

✅ Answer: The four fundamental biological molecules are:
✔ Carbohydrates – Made of C, H, O; provide energy & structural support (e.g., glucose, starch, cellulose).
✔ Proteins – Made of amino acids; function in enzymes, hormones, transport, and structure (e.g., hemoglobin, enzymes).
✔ Lipids – Made of fatty acids & glycerol; used for energy storage, insulation, and cell membranes (e.g., triglycerides, phospholipids).
✔ Nucleic Acids – Made of nucleotides; store & transmit genetic information (e.g., DNA, RNA).

6️⃣ Why is the covalent bond in water polar?

✅ Answer: The covalent bond in water (H₂O) is polar because:
✔ Oxygen is more electronegative than hydrogen, attracting electrons more strongly.
✔ This creates a partial negative charge (δ⁻) on oxygen and partial positive charges (δ⁺) on hydrogen, resulting in a dipole moment.
✔ This polarity allows water to form hydrogen bonds and act as a universal solvent.

7️⃣ Why is water regarded as a universal solvent?

✅ Answer: Water is called the universal solvent because:
✔ It dissolves many substances due to its polarity.
✔ Ionic compounds (e.g., NaCl) dissolve as water separates their ions.
✔ Polar covalent molecules (e.g., sugars, proteins) dissolve via hydrogen bonding.
✔ This property allows water to transport nutrients, remove waste, and support biochemical reactions in living organisms.

8️⃣ What is the importance of hydrogen bonding?

✅ Answer: Hydrogen bonding plays a crucial role in biological systems by:
✔ Stabilizing DNA – Holds base pairs (A=T, G≡C) together.
✔ Maintaining protein structure – Forms secondary & tertiary protein structures.
✔ Giving water unique properties – High cohesion, surface tension, and heat capacity.
✔ Supporting cellular function – Helps in enzyme-substrate binding and membrane integrity.

9️⃣ Why does a very large amount of heat increase the temperature of water only slightly?

✅ Answer: Water has a high specific heat capacity (4.18 J/g°C), meaning:
✔ A large amount of heat is needed to break hydrogen bonds before raising the temperature.
✔ This property allows cells & aquatic environments to maintain stable temperatures, protecting organisms from sudden temperature changes.

🔟 How does water protect living things against sudden thermal change?

✅ Answer: Water has a high specific heat capacity, meaning it absorbs and releases heat slowly. This helps:
✔ Maintain body temperature in living organisms.
✔ Protect aquatic life from extreme temperature fluctuations.
✔ Ensure enzyme stability, preventing protein denaturation.

1️⃣1️⃣ What is the importance of high heat of vaporization of water to animals?

✅ Answer: Water has a high heat of vaporization (574 cal/g), which helps:
✔ Cooling through evaporation – Sweating and panting remove excess body heat.
✔ Temperature regulation – Heat is absorbed before evaporation, stabilizing body temperature.
✔ Prevent dehydration – Slow evaporation rate conserves water in desert animals.

1️⃣2️⃣ Describe the classification of carbohydrates.

✅ Answer: Carbohydrates are classified into:
✔ Monosaccharides – Single sugar units (Glucose, Fructose).
✔ Disaccharides – Two monosaccharides linked by a glycosidic bond (Sucrose, Maltose, Lactose).
✔ Polysaccharides – Long chains of monosaccharides (Starch, Glycogen, Cellulose).

1️⃣3️⃣ Describe the classification of monosaccharides.

✅ Answer: Monosaccharides are classified based on:
✔ Number of Carbon Atoms:

Trioses (3C) – Glyceraldehyde.
Pentoses (5C) – Ribose, Deoxyribose.
Hexoses (6C) – Glucose, Fructose.
✔ Functional Group:
Aldoses – Contain an aldehyde (-CHO) group (e.g., Glucose).
Ketoses – Contain a ketone (-CO) group (e.g., Fructose).

1️⃣4️⃣ Describe the conversion of open-chain ribose into a ring chain.

✅ Answer:
✔ Ribose (a pentose sugar) exists in an open-chain form in dry state.
✔ In an aqueous solution, the -OH on C4 attacks the carbonyl carbon (C1), forming a furanose (5-membered) ring.
✔ This process is called intramolecular cyclization, creating α-ribose and β-ribose.

1️⃣5️⃣ Draw and label the ring forms of alpha and beta glucose.

✅ Answer:
✔ α-Glucose – The -OH on C1 is below the ring.
✔ β-Glucose – The -OH on C1 is above the ring.
✔ Both exist in pyranose (6-membered) ring form in solutions.

1️⃣6️⃣ Justify that the laboratory-manufactured sweeteners are 'left-handed' sugars and cannot be metabolized by 'right-handed' enzymes.

✅ Answer:
✔ Natural sugars are D-form (right-handed) and fit into enzyme active sites.
✔ Artificial sweeteners are L-form (left-handed), making them unrecognizable by digestive enzymes.
✔ Since enzymes are stereospecific, they cannot metabolize L-sugars, making them calorie-free.

1️⃣7️⃣ Illustrate the formation and breakage of:

✅ (a) Sucrose (b) Maltose (c) Lactose
✔ Formation – Disaccharides form via condensation (dehydration synthesis), where a glycosidic bond is formed, and a water molecule (H₂O) is removed.
✔ Breakage – Disaccharides are broken by hydrolysis, where water is added, breaking the glycosidic bond.

Disaccharide	Monosaccharides	Bond Type	Formation Process
Sucrose	Glucose + Fructose	α-1,2-glycosidic	Condensation
Maltose	Glucose + Glucose	α-1,4-glycosidic	Condensation
Lactose	Glucose + Galactose	β-1,4-glycosidic	Condensation

1️⃣8️⃣ Draw the structural formula of an amino acid.

✅ Answer:
✔ General structure of an amino acid:

$H₂N - CH(R) - COOH$

✔ Components:

Amino group (-NH₂)
Carboxyl group (-COOH)
Hydrogen atom (H)
Variable R group (Side chain) – determines amino acid type

1️⃣9️⃣ Describe the synthesis of a peptide bond.

✅ Answer:
✔ A peptide bond is formed between the carboxyl (-COOH) group of one amino acid and the amino (-NH₂) group of another.
✔ Condensation reaction removes H₂O to form a -CO-NH- (peptide bond).
✔ Example: Two amino acids forming a dipeptide.

2️⃣0️⃣ Describe the four types of protein structure

✅ Answer:

Level	Description	Example
Primary	Linear sequence of amino acids	Insulin
Secondary	Folding into α-helix or β-pleated sheet due to hydrogen bonding	Keratin, Silk
Tertiary	3D structure formed by disulfide, ionic, hydrogen bonds	Enzymes, Myoglobin
Quaternary	Two or more polypeptides form a functional protein	Hemoglobin, Collagen

2️⃣1️⃣ Describe:
✅ (a) Globular proteins

✔ Spherical, water-soluble, and functional proteins (e.g., enzymes, hemoglobin).

✅ (b) Fibrous proteins

✔ Long, insoluble, and structural proteins (e.g., collagen, keratin).

2️⃣2️⃣ Describe the classification of lipids.

✅ Answer: Lipids are classified into:

Type	Examples	Function
Simple Lipids	Triglycerides	Energy storage
Compound Lipids	Phospholipids, Glycolipids	Membrane structure
Derived Lipids	Steroids, Vitamins	Hormones, signaling

2️⃣3️⃣ What role do lipids play in living organisms?

✅ Answer:
✔ Energy storage – Provides 2× more energy than carbohydrates.
✔ Membrane formation – Phospholipids form cell membranes.
✔ Insulation & Protection – Fat stores insulate and cushion organs.
✔ Signaling molecules – Steroids regulate physiological functions.

2️⃣4️⃣ Why do phospholipids form a thin layer on the surface of an aqueous solution?

✅ Answer:
✔ Phospholipids are amphipathic – They have a hydrophilic (polar) head and hydrophobic (non-polar) tails.
✔ In water, they arrange in a monolayer with hydrophilic heads facing water and hydrophobic tails avoiding water.

2️⃣5️⃣ What is an isoprene unit? Explain.

✅ Answer:
✔ Isoprene unit (C₅H₈) is the basic building block of terpenes, steroids, and fat-soluble vitamins.
✔ Five-carbon structure that polymerizes to form natural rubber, carotenoids, and cholesterol precursors.

2️⃣6️⃣ Describe a steroid nucleus.

✅ Answer:
✔ A steroid nucleus is a four-ringed hydrocarbon structure (three 6-membered rings and one 5-membered ring).
✔ It is found in cholesterol, steroid hormones (testosterone, estrogen), and vitamin D.
✔ Steroids are hydrophobic and play key roles in membrane stability, signaling, and metabolism.

2️⃣7️⃣ How might an error in the DNA of an organism affect protein function?

✅ Answer:
✔ A mutation in DNA can change the amino acid sequence of a protein.
✔ This may result in:

Loss of function (e.g., sickle cell anemia due to a single amino acid change in hemoglobin).
Reduced enzyme activity or misfolded proteins.
Defective cell signaling, leading to diseases (e.g., cancer).

2️⃣8️⃣ Define a gene.

✅ Answer: A gene is a specific sequence of nucleotides in DNA that codes for the synthesis of a polypeptide or functional RNA.

✔ Genes determine traits, enzyme production, and cell functions.
✔ They follow the Central Dogma: DNA → RNA → Protein.

2️⃣9️⃣ Write the differences between:

✅ (a) Major and Minor Bioelements
✔ Major (99%) – C, H, O, N, P, S (found in macromolecules).
✔ Minor (<1%) – Ca, K, Na, Cl, Mg (used in nerve signaling, bones).

✅ (b) Dimer and Polymer
✔ Dimer – Two monomers linked (e.g., Maltose = Glucose + Glucose).
✔ Polymer – Many monomers linked (e.g., Starch, Proteins, DNA).

✅ (c) Polar and Non-Polar Covalent Bonds
✔ Polar – Unequal sharing of electrons (e.g., H₂O).
✔ Non-Polar – Equal sharing of electrons (e.g., O₂, CH₄).

✅ (d) Polyhydroxy Aldehyde and Polyhydroxy Ketone
✔ Aldehyde (-CHO) group in aldoses (e.g., Glucose).
✔ Ketone (-CO) group in ketoses (e.g., Fructose).

✅ (e) Alpha and Beta Glucose
✔ Alpha (α) Glucose – -OH on C1 is below the plane.
✔ Beta (β) Glucose – -OH on C1 is above the plane.

✅ (f) D-Glucose and L-Glucose
✔ D-Glucose – Found in nature, digestible by humans.
✔ L-Glucose – Synthetic, not metabolized by enzymes.

✅ (g) Amylose and Amylopectin
✔ Amylose – Linear, unbranched starch (α-1,4 bonds).
✔ Amylopectin – Branched starch (α-1,4 and α-1,6 bonds).

✅ (h) Amylopectin and Glycogen
✔ Amylopectin – Less branched, found in plants.
✔ Glycogen – Highly branched, stored in liver and muscles.

✅ (i) Primary and Secondary Structure of Proteins
✔ Primary – Linear sequence of amino acids.
✔ Secondary – Folding into α-helix or β-sheet (H-bonding).

✅ (j) Tertiary and Quaternary Structure of Proteins
✔ Tertiary – 3D folding due to disulfide & ionic bonds.
✔ Quaternary – Two or more polypeptides form a functional protein (e.g., Hemoglobin).

✅ (k) Purines and Pyrimidines
✔ Purines – Double-ringed bases (Adenine, Guanine).
✔ Pyrimidines – Single-ringed bases (Cytosine, Thymine, Uracil).

✅ (l) Saturated and Unsaturated Fatty Acids
✔ Saturated – No double bonds, solid at room temp (Butter).
✔ Unsaturated – Has double bonds, liquid at room temp (Olive oil).

✅ (m) DNA and RNA
✔ DNA – Double-stranded, stores genetic information.
✔ RNA – Single-stranded, helps in protein synthesis.

Biological Molecules Long Questions with answers from Chapter 2 (Federal Board, 11th Class):

30. Chemical Composition of Protoplasm

Protoplasm is the living substance of cells, consisting of:

Water (70–90%) – Solvent for biochemical reactions, maintains cell shape.
Proteins (10–15%) – Enzymes, structural components, signaling molecules.
Lipids (2–3%) – Membrane formation, energy storage.
Carbohydrates (1–2%) – Energy source, structural roles (e.g., glycocalyx).
Nucleic Acids (1%) – DNA, RNA for genetic information storage & transfer.
Inorganic Ions (1%) – Na⁺, K⁺, Ca²⁺, Cl⁻, Mg²⁺, involved in homeostasis, signaling.

31. Distinction of Biological Molecules

Property	Carbohydrates	Proteins	Lipids	Nucleic Acids
Monomers	Monosaccharides	Amino acids	Fatty acids & glycerol	Nucleotides
Elements	C, H, O	C, H, O, N (some S)	C, H, O (some P)	C, H, O, N, P
Function	Energy, structure	Enzymes, transport, immunity	Energy storage, membranes	Genetic information
Example	Glucose, starch	Hemoglobin, collagen	Phospholipids, steroids	DNA, RNA

32. Dehydration Synthesis & Hydrolysis Reactions

Dehydration synthesis: Joins monomers by removing water (e.g., peptide bond formation).
Hydrolysis: Breaks polymers by adding water (e.g., digestion of proteins).

Sketch:

Dehydration Synthesis:
- A—OH + B—H → A—B + H₂O
Hydrolysis:
- A—B + H₂O → A—OH + B—H

33. Properties of Water as the Cradle of Life

Cohesion & Adhesion – Maintains fluidity & transport in organisms.
High Heat Capacity – Stabilizes temperature.
Solvent Property – Universal solvent for biochemical reactions.
Density Anomaly – Ice floats, insulating aquatic life.
pH Buffering – Maintains stable internal pH.

34. Properties & Role of Monosaccharides

Properties:

Sweet, water-soluble, crystalline.
Reducing sugars (except ketoses).
Exist as linear & cyclic structures.

Roles:

Energy source (glucose).
Storage (glycogen, starch precursor).
Structural components (ribose in RNA, deoxyribose in DNA).

35. Empirical Formula & Classification of Monosaccharides

Empirical formula: (CH₂O)ₙ
Classification:
- Based on C-atoms: Triose (3C), Tetrose (4C), Pentose (5C), Hexose (6C).
- Based on functional group: Aldose (e.g., glucose), Ketose (e.g., fructose).

36. Stereoisomers of Glucose

D-Glucose & L-Glucose – Mirror images.
α-Glucose & β-Glucose – Differ in OH position at C1 (anomers).
Epimers – Differ at one C (e.g., glucose & galactose at C4).

37. Properties & Role of Disaccharides

Disaccharide	Composition	Properties	Role
Maltose	Glucose + Glucose	Reducing sugar	Starch digestion
Lactose	Glucose + Galactose	Reducing sugar	Energy in milk
Sucrose	Glucose + Fructose	Non-reducing sugar	Plant transport

38. Glycosidic Bond in Disaccharide Transport

Definition: Covalent bond between monosaccharides via dehydration.
Example: Sucrose transport in plants via phloem.
Enzyme: Sucrase hydrolyzes sucrose in digestion.

39. Properties & Role of Polysaccharides

Polysaccharide	Properties	Role
Starch	Insoluble, digestible	Plant energy storage
Glycogen	Highly branched	Animal energy storage
Cellulose	Fibrous, indigestible	Structural in plants
Chitin	Hard, polymer of N-acetylglucosamine	Exoskeleton in arthropods

40. Properties & Roles of Starch, Glycogen, Cellulose & Chitin

Starch – Plant storage, composed of amylose & amylopectin.
Glycogen – Animal glucose storage, stored in liver & muscles.
Cellulose – Structural, β(1→4) linked glucose in plant cell walls.
Chitin – Exoskeleton in insects, fungal cell walls.

41. Significance of Amino Acid Sequence (Sickle Cell Hb Example)

HbA (normal): Glu at position 6 of β-chain.
HbS (sickle cell): Glu → Val mutation causes hydrophobic interaction → sickle shape → occlusion → anemia.
Significance: Single AA change → altered protein function → disease.

42. Examples & Roles of Structural & Functional Proteins

Type	Examples	Role
Structural	Collagen, Keratin	Support, strength
Functional	Enzymes (amylase), Hormones (insulin)	Catalysis, regulation

Would you like any elaboration on specific topics?

43. Properties & Roles of Specific Lipids

(a) Acylglycerol (Triglycerides)

Properties:
- Esters of glycerol & fatty acids.
- Hydrophobic, energy-dense.
Roles:
- Major energy storage in adipose tissue.
- Insulation & organ protection.

(b) Phospholipids

Properties:
- Amphipathic (hydrophilic head, hydrophobic tail).
- Major component of cell membranes.
Roles:
- Forms lipid bilayer in membranes.
- Involved in cell signaling (e.g., phosphatidylinositol).

(c) Terpenes

Properties:
- Made of isoprene units (C₅H₈).
- Lipophilic, volatile.
Roles:
- Precursors to steroids, vitamins (A, K, E).
- Plant pigments (carotenoids), essential oils.

(d) Waxes

Properties:
- Long-chain fatty acids + alcohols.
- Water-resistant, solid at room temp.
Roles:
- Protective coatings (e.g., cuticle in plants, beeswax).
- Prevents dehydration in animals & plants.

44. Role of Specific Lipid Groups

(a) Steroids

Structure: Four fused rings (cyclopentanoperhydrophenanthrene).
Examples & Roles:
- Cholesterol – Membrane stability, precursor of bile acids.
- Hormones – Cortisol (stress), Estrogen/Testosterone (sex hormones).
- Vitamin D – Bone health, calcium metabolism.

(b) Prostaglandins

Structure: 20C fatty acids with a cyclopentane ring.
Roles:
- Inflammation, pain (prostaglandin E₂).
- Vasodilation/constriction (thromboxanes, prostacyclins).
- Uterine contractions (labor).

45. Molecular Structure of Nucleotides

Components:
- Pentose sugar (ribose or deoxyribose).
- Nitrogenous base (purine/pyrimidine).
- Phosphate group(s).
Types:
- Ribonucleotide (RNA) – Ribose sugar.
- Deoxyribonucleotide (DNA) – Deoxyribose sugar.

46. Nitrogenous Bases in Nucleotides

Type	Bases	Structure
Purines	Adenine (A), Guanine (G)	Double-ring
Pyrimidines	Cytosine (C), Thymine (T, in DNA), Uracil (U, in RNA)	Single-ring

47. Structure of ATP (Mononucleotide) & NAD (Dinucleotide)

(a) ATP (Adenosine Triphosphate)

Structure:
- Adenine (N-base) + Ribose + 3 phosphate groups.
Function:
- Universal energy currency.
- Hydrolysis releases energy for metabolism.

(b) NAD (Nicotinamide Adenine Dinucleotide)

Structure:
- Two nucleotides: Adenine + Nicotinamide.
Function:
- Electron carrier in redox reactions (cellular respiration).

48. Formation of Phosphodiester Bond

Definition: Covalent bond between 3’-OH of one nucleotide & 5’-phosphate of another.
Catalyzed by: DNA/RNA polymerase.
Role: Forms sugar-phosphate backbone of nucleic acids.

49. Watson & Crick's DNA Double Helix Model

Key Features:
- Two antiparallel strands.
- Sugar-phosphate backbone outside.
- Complementary base pairing (A-T, G-C) via H-bonds.
- Right-handed helical structure.
Significance: Stability, replication, genetic information storage.

50. Definition & Function of a Gene

Gene: DNA segment coding for a polypeptide/protein.
Gene Expression:
1. Transcription – DNA → mRNA.
2. Translation – mRNA → Protein (via ribosomes & tRNA).

51. General Structure of RNA

Single-stranded, but may fold into secondary structures.
Components: Ribose sugar, phosphate, nitrogenous bases (A, U, G, C).

52. Structure & Roles of Three Types of RNA

RNA Type	Structure	Role
mRNA	Linear, carries codons	Genetic message from DNA to ribosome
tRNA	Cloverleaf-shaped, anticodon region	Transfers amino acids to ribosome
rRNA	Component of ribosome	Catalyzes peptide bond formation

53. Roles of Conjugated Molecules

(a) Glycolipids

Structure: Lipid + carbohydrate.
Function: Cell recognition, membrane stability (e.g., blood group antigens).

(b) Glycoproteins

Structure: Protein + carbohydrate.
Function: Cell signaling, immune response (e.g., antibodies, receptors).

(c) Lipoproteins

Structure: Lipids + proteins.
Function: Transport lipids in blood (e.g., LDL, HDL in cholesterol transport).

(d) Nucleoproteins

Structure: Nucleic acids + proteins.
Function: DNA packaging (e.g., histones in chromatin), RNA-binding proteins.

Biological Molecules – Frequently Examined Questions (FEQs)

Short Conceptual Questions

What are bioelements? Classify them based on their abundance in living organisms.
Explain why water is considered a universal solvent.
Why does water have a high specific heat capacity, and how does it benefit living organisms?
Define the primary, secondary, tertiary, and quaternary structures of proteins with examples.
What are the key differences between globular and fibrous proteins?
Describe the different types of lipids and their biological functions.
Why do phospholipids arrange in a bilayer when placed in water?
What is an isoprene unit? Give an example of its biological significance.
Explain the difference between a polar and non-polar covalent bond with examples.
Differentiate between simple, compound, and derived lipids.

Diagram & Structural Questions

Draw and label the general structure of an amino acid.
Illustrate the formation and breakage of a peptide bond.
Draw the ring structures of alpha and beta glucose.
Illustrate the structural difference between aldoses and ketoses using glucose and fructose as examples.
Show the process of intramolecular cyclization of ribose into its ring form.

Application-Based Questions

How does an error in DNA affect protein function? Provide an example.
Justify why artificial sweeteners are non-metabolizable by the human body.
How does the high heat of vaporization of water help in thermoregulation?
Why do phospholipids form a monolayer at the surface of an aqueous solution?
Explain how hydrogen bonding contributes to the stability of DNA and protein structures.

Comparison-Based Questions

Differentiate between:

Major and minor bioelements.
Dimer and polymer.
Monosaccharides, disaccharides, and polysaccharides.
Peptide bond and glycosidic bond.
Starch and cellulose in terms of structure and function.

These FEQs cover conceptual, structural, application-based, and comparative aspects of biological molecules, making them useful for exams and revision. Let me know if you need more.

Understanding biological molecules is essential for grasping the fundamental principles of biochemistry and molecular biology. These molecules, including carbohydrates, proteins, lipids, and nucleic acids, play crucial roles in the structure and function of living organisms. By mastering the MCQs and short questions from Class 11 Chapter 2 (Federal Board), students can strengthen their concepts and prepare effectively for exams.

Chapter 2 Biological Molecules Exercise Solution 11 Class Biology Notes (FBISE, Best for Exams)