Carbohydrates are defined as optically active polyhydroxy aldehydes or ketones, or substances that yield such compounds on hydrolysis. They are classified by hydrolysis behaviour: monosaccharides cannot be hydrolysed further (glucose, fructose); oligosaccharides hydrolyse to give two to ten monosaccharide units, of which disaccharides are the most important; and polysaccharides hyd
Biomolecules
Class 1211 previous-year questions from this chapter every option and the correct answer, free · where the marks are
1. Carbohydrates
Exam focus: Sucrose is the classic non-reducing sugar because its glycosidic bond ties up both anomeric carbons — C1 of glucose and C2 of fructose — leaving no free anomeric OH to open into a reactive aldehyde or ketone, unlike maltose and lactose, which keep one free and do reduce Fehling's or Tollens'. This is also why sucrose shows no mutarotation, while glucose's optical rotation visibly drifts as its α and β anomers interconvert through the open-chain form.
Biomolecules: Carbohydrates
Physics Wallah - Alakh Pandey
Dedicated single-topic lecture on carbohydrates from a Biomolecules series.
ChemistryNEET 2025show ▾Sugar 'X':
A. is found in honey
B. is a keto sugar
C. exists in and anomeric forms
D. is laevorotatory
'X' is:
- A.D-Glucose
- B.D-Fructose✓
- C.Maltose
- D.Sucrose
Solution
Fructose is the keto-hexose found in honey, exists in and anomeric (furanose) forms, and is laevorotatory — hence 'laevulose'.
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Save for spaced revision (free account)ChemistryNEET 2024show ▾The reagents with which glucose does not react to give the corresponding tests/products are:
A. Tollens' reagent
B. Schiff's reagent
C. HCN
D.
E.
Choose the correct option from those given below:
- A.A and D
- B.B and E✓
- C.E and D
- D.B and C
Solution
Glucose has an aldehyde group, so it reduces Tollens' reagent and adds HCN and NHOH. It does not give the Schiff's test and does not form a bisulphite adduct with NaHSO — anomalies explained by its cyclic hemiacetal structure. So B and E.
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Save for spaced revision (free account)ChemistryNEET 2020show ▾Sucrose on hydrolysis gives:
- A.-D-glucose + -D-fructose
- B.-D-glucose + -D-glucose
- C.-D-glucose + -D-fructose✓
- D.-D-fructose + -D-fructose
The worked solution is part of a paid pack.
2. Proteins, enzymes and vitamins
Exam focus: Denaturation destroys a protein's secondary and tertiary structure, and its biological activity, but leaves the primary structure — the peptide-bonded amino acid sequence — untouched. Fat-soluble vitamins (A, D, E, K) get stored in body fat and can reach toxic levels on overdose; water-soluble ones (B-complex, C) aren't stored and must come from the diet regularly, which is why their deficiencies (scurvy for C, beriberi for B₁) show up faster.
Biomolecules — Full Chapter (incl. Proteins, Enzymes, Vitamins)
Competition Wallah
Full-chapter video; no video dedicated only to proteins/enzymes/vitamins could be verified, so this covers them bundled with carbohydrates and nucleic acids.
ChemistryNEET 2025show ▾Match List I with List II.
List I (Name of vitamin) List II (Deficiency disease) A. Vitamin I. Cheilosis B. Vitamin D II. Convulsions C. Vitamin III. Rickets D. Vitamin IV. Pernicious anaemia
Choose the correct answer from the options given below:
- A.A-I, B-III, C-II, D-IV
- B.A-IV, B-III, C-I, D-II✓
- C.A-II, B-III, C-I, D-IV
- D.A-IV, B-III, C-II, D-I
Solution
Vitamin deficiency causes pernicious anaemia (IV); vitamin D, rickets (III); vitamin riboflavin), cheilosis (I); vitamin pyridoxine), convulsions (II).
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Save for spaced revision (free account)ChemistryNEET 2022show ▾The incorrect statement regarding enzymes is:
- A.Enzymes are very specific for a particular reaction and substrate
- B.Enzymes are biocatalysts
- C.Like chemical catalysts, enzymes reduce the activation energy of bio-processes
- D.Enzymes are polysaccharides✓
The worked solution is part of a paid pack.
ChemistryNEET 2021show ▾RBC deficiency is a deficiency disease of:
- A.Vitamin ✓
- B.Vitamin
- C.Vitamin
- D.Vitamin
The worked solution is part of a paid pack.
ChemistryNEET 2020show ▾Which of the following is a basic amino acid?
- A.Serine
- B.Alanine
- C.Tyrosine
- D.Lysine✓
The worked solution is part of a paid pack.
ChemistryNEET 2020show ▾The following metal ion activates many enzymes, participates in the oxidation of glucose to produce ATP, and, with sodium, is responsible for the transmission of nerve signals.
- A.Iron
- B.Copper
- C.Calcium
- D.Potassium✓
The worked solution is part of a paid pack.
ChemistryNEET 2019show ▾Enzymes that utilise ATP in phosphate transfer require an alkaline earth metal (M) as a cofactor. M is:
ChemistryNEET 2019show ▾The non-essential amino acid among the following is:
- A.Valine
- B.Leucine
- C.Alanine✓
- D.Lysine
The worked solution is part of a paid pack.
3. Nucleic acids
Exam focus: Chargaff's rule lets you find all four base percentages in double-stranded DNA from just one — %A = %T and %G = %C, so purines always equal pyrimidines overall, a calculation NEET poses directly. Structurally: DNA's sugar is deoxyribose (no 2'-OH) against RNA's ribose, DNA pairs A with T using 2 hydrogen bonds where RNA substitutes uracil for thymine, and G pairs with C using 3 — so a strand richer in G-C is more thermally stable.
Biomolecules: Lipids and Nucleic Acids
Physics Wallah - Alakh Pandey
Covers nucleic-acid structure (DNA/RNA) bundled together with lipids in the same lecture.
ChemistryNEET 2023show ▾Given below are two statements:
Statement I: A unit formed by the attachment of a base to the 1′ position of a sugar is known as a nucleoside.
Statement II: When a nucleoside is linked to phosphorous acid at the 5′-position of the sugar moiety, we get a nucleotide.
In the light of the above statements, choose the correct answer from the options given below:
- A.Both Statement I and Statement II are true
- B.Both Statement I and Statement II are false
- C.Statement I is true but Statement II is false✓
- D.Statement I is false but Statement II is true
The worked solution is part of a paid pack.