Quick answer: A biomolecules chemistry NEET PYQ analysis shows that NTA asks about one to two questions a year from the Class 12 Chemistry chapter Biomolecules, and most come from four areas: carbohydrates (glucose reactions, reducing and non-reducing sugars, glycosidic linkages in sucrose, maltose, lactose and starch), proteins (amino acids, peptide bonds, levels of structure and denaturation), vitamins and their deficiency diseases, and nucleic acids (DNA vs RNA, nucleosides and nucleotides). It is one of the most direct NCERT chapters in Organic Chemistry.
This guide breaks down what NTA repeats, the tables you must know and PYQ-pattern questions with answers. For chapter notes, use our Biomolecules class 12 notes.
Want to test yourself first? Solve the Biomolecules Chemistry PYQs for free, then use this guide to fix the gaps.
Table of Contents
Why This Chapter Is Easy Chemistry Marks
Unlike most Organic chapters, Biomolecules has almost no mechanisms. Its questions test NCERT facts: which sugar is non-reducing, which vitamin cures scurvy, which base is missing in RNA. That makes it one of the fastest chapters to score in. To see where it sits among other chapters, check the NEET 2027 chapter weightage, and for a quick warm-up, try these five quick Biomolecules questions.
Biology has its own Biomolecules chapter, focused on enzymes and metabolites; our Biology Biomolecules PYQ analysis covers that side. The carbonyl reactions of glucose build on our Aldehydes and Ketones PYQ analysis.
Biomolecules Chemistry NEET PYQ Analysis: What NTA Repeats
When you sort the past NEET chemistry PYQs from this chapter, four question types cover nearly everything.
| Question type | Frequency | What it tests |
|---|---|---|
| Carbohydrates | Most frequent | Glucose reactions and structure, reducing sugars, glycosidic linkages, starch and glycogen |
| Proteins and amino acids | Very frequent | Essential amino acids, zwitterions, peptide bond, α-helix, denaturation |
| Vitamins | Regular | Fat-soluble vs water-soluble, deficiency diseases |
| Nucleic acids | Regular | Sugars and bases in DNA and RNA, nucleosides vs nucleotides, base pairing |
Glucose: Reactions That Prove Its Structure
| Reaction | Product | What it shows |
|---|---|---|
| Heating with HI | n-Hexane | Six carbons in a straight chain |
| With hydroxylamine | Oxime | A carbonyl group |
| With HCN | Cyanohydrin | A carbonyl group |
| With bromine water | Gluconic acid | The carbonyl is an aldehyde |
| Acetylation with acetic anhydride | Glucose pentaacetate | Five –OH groups |
| Oxidation with nitric acid | Saccharic acid | A primary alcohol group |
Glucose does not give Schiff’s test or form an addition product with NaHSO₃, and its pentaacetate does not react with hydroxylamine. These facts show that glucose mostly exists in a cyclic (pyranose) form. The two cyclic forms that differ only at C1 are the α and β anomers.
Reducing Sugars and Glycosidic Linkages
Reducing sugars reduce Fehling’s solution and Tollens’ reagent because they have a free aldehyde or ketone group. All monosaccharides are reducing sugars.
| Sugar | Units | Linkage | Reducing? |
|---|---|---|---|
| Sucrose | α-D-glucose + β-D-fructose | C1 (glucose) – C2 (fructose) | No |
| Maltose | Two α-D-glucose | C1 – C4 | Yes |
| Lactose (milk sugar) | β-D-galactose + β-D-glucose | C1 – C4 | Yes |
Sucrose is dextrorotatory, but its hydrolysis gives a laevorotatory mixture called invert sugar, because fructose’s laevorotation (−92.4°) is larger than glucose’s dextrorotation (+52.5°).
| Polysaccharide | Structure |
|---|---|
| Amylose (15–20% of starch) | Water-soluble, unbranched, α-D-glucose with C1–C4 linkages |
| Amylopectin (80–85% of starch) | Water-insoluble, branched, C1–C4 chains with C1–C6 branches |
| Glycogen (animal starch) | Highly branched, like amylopectin; stored in liver, muscles and brain |
| Cellulose | Unbranched chain of β-D-glucose with C1–C4 linkages |
Proteins and Amino Acids
- There are ten essential amino acids that the body cannot make: valine, leucine, isoleucine, arginine, lysine, threonine, methionine, phenylalanine, tryptophan and histidine.
- In solution, amino acids exist as a zwitterion, with both a positive and a negative charge, so they behave like salts and have high melting points.
- Glycine is the only common amino acid that is not optically active.
- A peptide bond is the –CO–NH– amide link between two amino acids.
- Proteins are fibrous (keratin in hair, myosin in muscle; insoluble in water) or globular (insulin, albumins; soluble).
Protein structure at four levels:
| Level | What holds it |
|---|---|
| Primary | Sequence of amino acids joined by peptide bonds |
| Secondary | Hydrogen bonds: α-helix (right-handed, –NH of one unit bonds to C=O of the fourth unit along) or β-pleated sheet |
| Tertiary | Hydrogen bonds, disulphide links, van der Waals and electrostatic forces |
| Quaternary | Arrangement of two or more polypeptide subunits |
Denaturation destroys the secondary and tertiary structure but leaves the primary structure intact. NCERT examples: egg white coagulating on boiling, and milk curdling from lactic acid made by bacteria.
Vitamins and Deficiency Diseases
Vitamins A, D, E and K are fat-soluble and stored in the liver and adipose tissue. The B-group vitamins and vitamin C are water-soluble, pass out in urine and must be supplied regularly in the diet; vitamin B₁₂ is the exception that can be stored.
| Vitamin | Deficiency disease |
|---|---|
| A | Xerophthalmia, night blindness |
| B₁ (thiamine) | Beriberi |
| B₂ (riboflavin) | Cheilosis (cracked lips), digestive disorders |
| B₆ (pyridoxine) | Convulsions |
| B₁₂ | Pernicious anaemia |
| C (ascorbic acid) | Scurvy (bleeding gums) |
| D | Rickets in children, osteomalacia in adults |
| E | Increased fragility of RBCs, muscular weakness |
| K | Increased blood clotting time |
Vitamin deficiency matching appears regularly, and the B₁, C and D rows are the most common picks.
Nucleic Acids
| Feature | DNA | RNA |
|---|---|---|
| Sugar | β-D-2-deoxyribose | β-D-ribose |
| Bases | Adenine, guanine, cytosine, thymine | Adenine, guanine, cytosine, uracil |
| Structure | Double helix (Watson and Crick) | Usually single-stranded |
| Types | — | mRNA, rRNA, tRNA |
- A nucleoside is a base joined to C1′ of the sugar. A nucleotide also has a phosphate at C5′.
- Nucleotides join by phosphodiester links between the 5′ and 3′ carbons of adjacent sugars.
- In DNA, A pairs with T through two hydrogen bonds, and G pairs with C through three.
Worked PYQ-Pattern Questions
Q1. Which of these is a non-reducing sugar? (a) Glucose (b) Maltose (c) Sucrose (d) Lactose
Answer: (c) Sucrose. The reducing groups of both glucose and fructose are used in its glycosidic bond.
Q2. Prolonged heating of glucose with HI gives:
Answer: n-Hexane, showing that its six carbons are in a straight chain.
Q3. Why is the hydrolysis product of sucrose called invert sugar?
Answer: Sucrose is dextrorotatory, but the mixture of glucose (+52.5°) and fructose (−92.4°) formed on hydrolysis is laevorotatory, so the sign of rotation inverts.
Q4. Deficiency of which vitamin causes beriberi? (a) Vitamin A (b) Vitamin B₁ (c) Vitamin C (d) Vitamin D
Answer: (b) Vitamin B₁ (thiamine).
Q5. On denaturation, which structure of a protein stays intact?
Answer: The primary structure. Secondary and tertiary structures are destroyed.
Q6. Which base is found in RNA but not in DNA?
Answer: Uracil. DNA has thymine instead.
Common Traps in This Chapter
- Calling sucrose a reducing sugar
- Mixing up the C1–C4 links of maltose and lactose with the C1–C2 link of sucrose
- Saying amylose is branched (amylopectin is branched)
- Thinking denaturation breaks peptide bonds
- Listing vitamin B₁₂ as a vitamin that cannot be stored
- Putting ribose in DNA or thymine in RNA
Practise Every Biomolecules Chemistry PYQ
This biomolecules chemistry NEET PYQ analysis shows you where the marks are. Solving real past questions makes the tables automatic. Every Biomolecules previous year question from Chemistry is available chapter-wise, free:
👉 Solve all Biomolecules Chemistry NEET PYQs
Keep the sugar, vitamin and DNA–RNA tables beside you for the first round, then solve the second round without them.
Conclusion
Biomolecules is the most fact-based chapter in NEET Organic Chemistry. Use this biomolecules chemistry NEET PYQ analysis to master the glucose reactions, reducing sugars and linkages, protein structure and denaturation, vitamins and nucleic acids. Then practise the past questions until each answer comes without thinking.
❓ FAQ
Q: How many questions come from Biomolecules in NEET Chemistry? A: Usually one to two questions a year, mostly on carbohydrates, vitamins, proteins or nucleic acids.
Q: What is the most important topic in Chemistry Biomolecules for NEET? A: Carbohydrates are the most tested, especially glucose reactions, reducing vs non-reducing sugars and the linkages in sucrose, maltose, lactose and starch.
Q: Why is sucrose a non-reducing sugar? A: Its glycosidic bond joins C1 of glucose to C2 of fructose, so neither unit has a free aldehyde or ketone group to reduce Fehling’s or Tollens’ reagent.
Q: Which vitamins are fat-soluble? A: Vitamins A, D, E and K. They are stored in the liver and adipose tissue.
Q: How is the Chemistry Biomolecules chapter different from the Biology one? A: Chemistry focuses on carbohydrate reactions, protein structure, vitamins and nucleic acid chemistry. Biology focuses more on enzymes, metabolites and the analysis of tissues.
Q: Where can I practise Biomolecules Chemistry NEET PYQs for free? A: You can solve every Chemistry Biomolecules previous year question chapter-wise for free using the practice links in this article.