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Biomolecules: questions with answers

Class 12 Chemistry, Chapter 10 (NCERT). 15 questions by concept. Open “Show answer” for the answer and why.

How to teach this chapter · Common misconceptions & worked visual for this chapter

Carbohydrate classification and structure

Question 1

Which statement gives the correct Class XII chemistry for ‘Carbohydrate classification and structure’?

  1. (a)For carbohydrate classification and structure, the relevant direction, trend, product ordering, or cause-and-effect relation is always the exact reverse of the governing rule.
  2. (b)Only the name of the substance is needed for carbohydrate classification and structure; equations, structures, stoichiometry, evidence, and conditions cannot change the answer.
  3. (c)The same conclusion about carbohydrate classification and structure remains valid after changing the reagent, molecular structure, medium, or condition that controls the result.
  4. (d)Carbohydrates are classified by hydrolysis and carbonyl type. Glucose and fructose form cyclic hemiacetal or hemiketal structures with anomers. Glycosidic linkage determines reducing behaviour and the properties of disaccharides and polysaccharides.
Show answer

(d) Carbohydrates are classified by hydrolysis and carbonyl type. Glucose and fructose form cyclic hemiacetal or hemiketal structures with anomers. Glycosidic linkage determines reducing behaviour and the properties of disaccharides and polysaccharides.

Carbohydrates are classified by hydrolysis and carbonyl type. Glucose and fructose form cyclic hemiacetal or hemiketal structures with anomers; glycosidic linkage determines reducing behaviour and the properties of disaccharides and polysaccharides.

Question 2

Which principle should be kept in mind when checking a conclusion about ‘Carbohydrate classification and structure’?

  1. (a)Only the name of the substance is needed for carbohydrate classification and structure; equations, structures, stoichiometry, evidence, and conditions cannot change the answer.
  2. (b)Carbohydrates are classified by hydrolysis and carbonyl type. Glucose and fructose form cyclic hemiacetal or hemiketal structures with anomers. Glycosidic linkage determines reducing behaviour and the properties of disaccharides and polysaccharides.
  3. (c)For carbohydrate classification and structure, the relevant direction, trend, product ordering, or cause-and-effect relation is always the exact reverse of the governing rule.
  4. (d)The same conclusion about carbohydrate classification and structure remains valid after changing the reagent, molecular structure, medium, or condition that controls the result.
Show answer

(b) Carbohydrates are classified by hydrolysis and carbonyl type. Glucose and fructose form cyclic hemiacetal or hemiketal structures with anomers. Glycosidic linkage determines reducing behaviour and the properties of disaccharides and polysaccharides.

Carbohydrates are classified by hydrolysis and carbonyl type. Glucose and fructose form cyclic hemiacetal or hemiketal structures with anomers; glycosidic linkage determines reducing behaviour and the properties of disaccharides and polysaccharides.

Question 3

Which statement survives a structure, equation, reagent, and condition audit for carbohydrate classification and structure?

  1. (a)Only the name of the substance is needed for carbohydrate classification and structure; equations, structures, stoichiometry, evidence, and conditions cannot change the answer.
  2. (b)Carbohydrates are classified by hydrolysis and carbonyl type. Glucose and fructose form cyclic hemiacetal or hemiketal structures with anomers. Glycosidic linkage determines reducing behaviour and the properties of disaccharides and polysaccharides.
  3. (c)For carbohydrate classification and structure, the relevant direction, trend, product ordering, or cause-and-effect relation is always the exact reverse of the governing rule.
  4. (d)The same conclusion about carbohydrate classification and structure remains valid after changing the reagent, molecular structure, medium, or condition that controls the result.
Show answer

(b) Carbohydrates are classified by hydrolysis and carbonyl type. Glucose and fructose form cyclic hemiacetal or hemiketal structures with anomers. Glycosidic linkage determines reducing behaviour and the properties of disaccharides and polysaccharides.

Carbohydrates are classified by hydrolysis and carbonyl type. Glucose and fructose form cyclic hemiacetal or hemiketal structures with anomers; glycosidic linkage determines reducing behaviour and the properties of disaccharides and polysaccharides.

Amino acids and protein structure

Question 4

Which statement gives the correct Class XII chemistry for ‘Amino acids and protein structure’?

  1. (a)For amino acids and protein structure, the relevant direction, trend, product ordering, or cause-and-effect relation is always the exact reverse of the governing rule.
  2. (b)Only the name of the substance is needed for amino acids and protein structure; equations, structures, stoichiometry, evidence, and conditions cannot change the answer.
  3. (c)Amino acids exist as zwitterions and form peptide bonds by condensation. Protein primary sequence folds into secondary, tertiary, and sometimes quaternary structures. Denaturation disrupts higher-order structure without normally hydrolysing peptide bonds.
  4. (d)The same conclusion about amino acids and protein structure remains valid after changing the reagent, molecular structure, medium, or condition that controls the result.
Show answer

(c) Amino acids exist as zwitterions and form peptide bonds by condensation. Protein primary sequence folds into secondary, tertiary, and sometimes quaternary structures. Denaturation disrupts higher-order structure without normally hydrolysing peptide bonds.

Amino acids exist as zwitterions and form peptide bonds by condensation. Protein primary sequence folds into secondary, tertiary, and sometimes quaternary structures; denaturation disrupts higher-order structure without normally hydrolysing peptide bonds.

Question 5

Which principle should be kept in mind when checking a conclusion about ‘Amino acids and protein structure’?

  1. (a)For amino acids and protein structure, the relevant direction, trend, product ordering, or cause-and-effect relation is always the exact reverse of the governing rule.
  2. (b)Only the name of the substance is needed for amino acids and protein structure; equations, structures, stoichiometry, evidence, and conditions cannot change the answer.
  3. (c)The same conclusion about amino acids and protein structure remains valid after changing the reagent, molecular structure, medium, or condition that controls the result.
  4. (d)Amino acids exist as zwitterions and form peptide bonds by condensation. Protein primary sequence folds into secondary, tertiary, and sometimes quaternary structures. Denaturation disrupts higher-order structure without normally hydrolysing peptide bonds.
Show answer

(d) Amino acids exist as zwitterions and form peptide bonds by condensation. Protein primary sequence folds into secondary, tertiary, and sometimes quaternary structures. Denaturation disrupts higher-order structure without normally hydrolysing peptide bonds.

Amino acids exist as zwitterions and form peptide bonds by condensation. Protein primary sequence folds into secondary, tertiary, and sometimes quaternary structures; denaturation disrupts higher-order structure without normally hydrolysing peptide bonds.

Question 6

Which statement survives a structure, equation, reagent, and condition audit for amino acids and protein structure?

  1. (a)The same conclusion about amino acids and protein structure remains valid after changing the reagent, molecular structure, medium, or condition that controls the result.
  2. (b)Only the name of the substance is needed for amino acids and protein structure; equations, structures, stoichiometry, evidence, and conditions cannot change the answer.
  3. (c)For amino acids and protein structure, the relevant direction, trend, product ordering, or cause-and-effect relation is always the exact reverse of the governing rule.
  4. (d)Amino acids exist as zwitterions and form peptide bonds by condensation. Protein primary sequence folds into secondary, tertiary, and sometimes quaternary structures. Denaturation disrupts higher-order structure without normally hydrolysing peptide bonds.
Show answer

(d) Amino acids exist as zwitterions and form peptide bonds by condensation. Protein primary sequence folds into secondary, tertiary, and sometimes quaternary structures. Denaturation disrupts higher-order structure without normally hydrolysing peptide bonds.

Amino acids exist as zwitterions and form peptide bonds by condensation. Protein primary sequence folds into secondary, tertiary, and sometimes quaternary structures; denaturation disrupts higher-order structure without normally hydrolysing peptide bonds.

Enzymes and biochemical catalysis

Question 7

Which statement gives the sound Class XII chemistry for ‘Enzymes and biochemical catalysis’?

  1. (a)Enzymes are highly selective biological catalysts whose activity depends on substrate binding, temperature, pH, and structure. They lower activation energy but do not change equilibrium, and loss of conformation can destroy activity.
  2. (b)For enzymes and biochemical catalysis, the relevant direction, trend, product ordering, or cause-and-effect relation is always the exact reverse of the governing rule.
  3. (c)The same conclusion about enzymes and biochemical catalysis remains valid after changing the reagent, molecular structure, medium, or condition that controls the result.
  4. (d)Only the name of the substance is needed for enzymes and biochemical catalysis; equations, structures, stoichiometry, evidence, and conditions cannot change the answer.
Show answer

(a) Enzymes are highly selective biological catalysts whose activity depends on substrate binding, temperature, pH, and structure. They lower activation energy but do not change equilibrium, and loss of conformation can destroy activity.

Enzymes are highly selective biological catalysts whose activity depends on substrate binding, temperature, pH, and structure. They lower activation energy but do not change equilibrium, and loss of conformation can destroy activity.

Question 8

Which principle should be retained when checking an inference about ‘Enzymes and biochemical catalysis’?

  1. (a)For enzymes and biochemical catalysis, the relevant direction, trend, product ordering, or cause-and-effect relation is always the exact reverse of the governing rule.
  2. (b)The same conclusion about enzymes and biochemical catalysis remains valid after changing the reagent, molecular structure, medium, or condition that controls the result.
  3. (c)Enzymes are highly selective biological catalysts whose activity depends on substrate binding, temperature, pH, and structure. They lower activation energy but do not change equilibrium, and loss of conformation can destroy activity.
  4. (d)Only the name of the substance is needed for enzymes and biochemical catalysis; equations, structures, stoichiometry, evidence, and conditions cannot change the answer.
Show answer

(c) Enzymes are highly selective biological catalysts whose activity depends on substrate binding, temperature, pH, and structure. They lower activation energy but do not change equilibrium, and loss of conformation can destroy activity.

Enzymes are highly selective biological catalysts whose activity depends on substrate binding, temperature, pH, and structure. They lower activation energy but do not change equilibrium, and loss of conformation can destroy activity.

Question 9

Which statement survives a structure, equation, reagent, and condition audit for enzymes and biochemical catalysis?

  1. (a)Only the name of the substance is needed for enzymes and biochemical catalysis; equations, structures, stoichiometry, evidence, and conditions cannot change the answer.
  2. (b)Enzymes are highly selective biological catalysts whose activity depends on substrate binding, temperature, pH, and structure. They lower activation energy but do not change equilibrium, and loss of conformation can destroy activity.
  3. (c)For enzymes and biochemical catalysis, the relevant direction, trend, product ordering, or cause-and-effect relation is always the exact reverse of the governing rule.
  4. (d)The same conclusion about enzymes and biochemical catalysis remains valid after changing the reagent, molecular structure, medium, or condition that controls the result.
Show answer

(b) Enzymes are highly selective biological catalysts whose activity depends on substrate binding, temperature, pH, and structure. They lower activation energy but do not change equilibrium, and loss of conformation can destroy activity.

Enzymes are highly selective biological catalysts whose activity depends on substrate binding, temperature, pH, and structure. They lower activation energy but do not change equilibrium, and loss of conformation can destroy activity.

Vitamins and deficiency

Question 10

Which statement gives the correct Class XII chemistry for ‘Vitamins and deficiency’?

  1. (a)Vitamins are required in small amounts and are grouped as water- or fat-soluble. Each vitamin has characteristic functions and deficiency diseases. Solubility affects storage and excess risk, so one vitamin cannot be swapped for another.
  2. (b)Only the name of the substance is needed for vitamins and deficiency; equations, structures, stoichiometry, evidence, and conditions cannot change the answer.
  3. (c)The same conclusion about vitamins and deficiency remains valid after changing the reagent, molecular structure, medium, or condition that controls the result.
  4. (d)For vitamins and deficiency, the relevant direction, trend, product ordering, or cause-and-effect relation is always the exact reverse of the governing rule.
Show answer

(a) Vitamins are required in small amounts and are grouped as water- or fat-soluble. Each vitamin has characteristic functions and deficiency diseases. Solubility affects storage and excess risk, so one vitamin cannot be swapped for another.

Vitamins are required in small amounts and are grouped as water- or fat-soluble. Each vitamin has characteristic functions and deficiency diseases; solubility affects storage and excess risk, so vitamin identities are not interchangeable.

Question 11

Which principle should be kept in mind when checking a conclusion about ‘Vitamins and deficiency’?

  1. (a)Vitamins are required in small amounts and are grouped as water- or fat-soluble. Each vitamin has characteristic functions and deficiency diseases. Solubility affects storage and excess risk, so one vitamin cannot be swapped for another.
  2. (b)For vitamins and deficiency, the relevant direction, trend, product ordering, or cause-and-effect relation is always the exact reverse of the governing rule.
  3. (c)The same conclusion about vitamins and deficiency remains valid after changing the reagent, molecular structure, medium, or condition that controls the result.
  4. (d)Only the name of the substance is needed for vitamins and deficiency; equations, structures, stoichiometry, evidence, and conditions cannot change the answer.
Show answer

(a) Vitamins are required in small amounts and are grouped as water- or fat-soluble. Each vitamin has characteristic functions and deficiency diseases. Solubility affects storage and excess risk, so one vitamin cannot be swapped for another.

Vitamins are required in small amounts and are grouped as water- or fat-soluble. Each vitamin has characteristic functions and deficiency diseases; solubility affects storage and excess risk, so vitamin identities are not interchangeable.

Nucleic acids and genetic information

Question 12

Which statement gives the sound Class XII chemistry for ‘Nucleic acids and genetic information’?

  1. (a)Only the name of the substance is needed for nucleic acids and genetic information; equations, structures, stoichiometry, evidence, and conditions cannot change the answer.
  2. (b)Nucleotides contain a base, pentose sugar, and phosphate and join through phosphodiester bonds. DNA and RNA differ in sugar, bases, typical structure, and biological roles; complementary base pairing supports replication and information transfer.
  3. (c)For nucleic acids and genetic information, the relevant direction, trend, product ordering, or cause-and-effect relation is always the exact reverse of the governing rule.
  4. (d)The same conclusion about nucleic acids and genetic information remains valid after changing the reagent, molecular structure, medium, or condition that controls the result.
Show answer

(b) Nucleotides contain a base, pentose sugar, and phosphate and join through phosphodiester bonds. DNA and RNA differ in sugar, bases, typical structure, and biological roles; complementary base pairing supports replication and information transfer.

Nucleotides contain a base, pentose sugar, and phosphate and join through phosphodiester bonds. DNA and RNA differ in sugar, bases, typical structure, and biological roles; complementary base pairing supports replication and information transfer.

Question 13

Which principle should be retained when checking an inference about ‘Nucleic acids and genetic information’?

  1. (a)For nucleic acids and genetic information, the relevant direction, trend, product ordering, or cause-and-effect relation is always the exact reverse of the governing rule.
  2. (b)The same conclusion about nucleic acids and genetic information remains valid after changing the reagent, molecular structure, medium, or condition that controls the result.
  3. (c)Only the name of the substance is needed for nucleic acids and genetic information; equations, structures, stoichiometry, evidence, and conditions cannot change the answer.
  4. (d)Nucleotides contain a base, pentose sugar, and phosphate and join through phosphodiester bonds. DNA and RNA differ in sugar, bases, typical structure, and biological roles; complementary base pairing supports replication and information transfer.
Show answer

(d) Nucleotides contain a base, pentose sugar, and phosphate and join through phosphodiester bonds. DNA and RNA differ in sugar, bases, typical structure, and biological roles; complementary base pairing supports replication and information transfer.

Nucleotides contain a base, pentose sugar, and phosphate and join through phosphodiester bonds. DNA and RNA differ in sugar, bases, typical structure, and biological roles; complementary base pairing supports replication and information transfer.

Hormones and chemical signalling

Question 14

Which statement gives the sound Class XII chemistry for ‘Hormones and chemical signalling’?

  1. (a)Only the name of the substance is needed for hormones and chemical signalling; equations, structures, stoichiometry, evidence, and conditions cannot change the answer.
  2. (b)For hormones and chemical signalling, the relevant direction, trend, product ordering, or cause-and-effect relation is always the exact reverse of the governing rule.
  3. (c)Hormones are chemical messengers produced in small amounts and act on specific targets. Their structures and functions vary, so endocrine effects and deficiency or excess states must be assigned to the correct hormone rather than generalised.
  4. (d)The same conclusion about hormones and chemical signalling remains valid after changing the reagent, molecular structure, medium, or condition that controls the result.
Show answer

(c) Hormones are chemical messengers produced in small amounts and act on specific targets. Their structures and functions vary, so endocrine effects and deficiency or excess states must be assigned to the correct hormone rather than generalised.

Hormones are chemical messengers produced in small amounts and act on specific targets. Their structures and functions vary, so endocrine effects and deficiency or excess states must be assigned to the correct hormone rather than generalised.

Question 15

Which principle should be retained when checking an inference about ‘Hormones and chemical signalling’?

  1. (a)Only the name of the substance is needed for hormones and chemical signalling; equations, structures, stoichiometry, evidence, and conditions cannot change the answer.
  2. (b)For hormones and chemical signalling, the relevant direction, trend, product ordering, or cause-and-effect relation is always the exact reverse of the governing rule.
  3. (c)Hormones are chemical messengers produced in small amounts and act on specific targets. Their structures and functions vary, so endocrine effects and deficiency or excess states must be assigned to the correct hormone rather than generalised.
  4. (d)The same conclusion about hormones and chemical signalling remains valid after changing the reagent, molecular structure, medium, or condition that controls the result.
Show answer

(c) Hormones are chemical messengers produced in small amounts and act on specific targets. Their structures and functions vary, so endocrine effects and deficiency or excess states must be assigned to the correct hormone rather than generalised.

Hormones are chemical messengers produced in small amounts and act on specific targets. Their structures and functions vary, so endocrine effects and deficiency or excess states must be assigned to the correct hormone rather than generalised.

Common misconception in Biomolecules

Open full misconception guide →

Is every disaccharide made with glucose reducing?

Wrong

Sucrose must be reducing because one of its units is glucose.

Why it feels right. Free glucose is reducing, so I expect its property to carry over unchanged.

Right

A disaccharide needs an available anomeric centre that can open to a reactive form.

Worked example

Maltose
One free anomeric centre→Reducing
Sucrose
Both anomeric centres joined→Nonreducing
The key difference is whether an anomeric centre is available. Both centres participate in sucrose's bond.
  1. In maltose, one anomeric centre is free.
  2. In sucrose, the glycosidic bond joins both anomeric centres.
  3. Maltose is reducing and sucrose is nonreducing.