Biomolecules – Carbohydrates: NEET MCQs with Answers

15 free questions on Biomolecules – Carbohydrates for NEET (UG), starting with previous-year NEET and AIPMT questions. Try each one, then tap Show answer for the answer and a short explanation.

Syllabus covered: Carbohydrates: structure and function

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Question 1

Previous-year question
Two statements are given below. Choose the correct option. [NEET 2022 (Overseas)]
Statement I: Cellulose is a polymeric polysaccharide.
Statement II: Glucose molecules are the building blocks of cellulose.
  1. Statement I is incorrect but Statement II is correct
  2. Both Statement I and Statement II are correct
  3. Both Statement I and Statement II are incorrect
  4. Statement I is correct but Statement II is incorrect
Show answer
Answer: (B) Both Statement I and Statement II are correct
Explanation: Cellulose is a polymeric homopolysaccharide (Statement I true), and it is built of glucose monomers linked by β-1,4 glycosidic bonds (Statement II true). Hence both statements are correct.

Question 2

Previous-year question
Identify the substances having a glycosidic bond and a peptide bond respectively in their structure. [NEET 2020]
  1. Glycerol, trypsin
  2. Cellulose, lecithin
  3. Inulin, insulin
  4. Chitin, cholesterol
Show answer
Answer: (C) Inulin, insulin
Explanation: Inulin is a polysaccharide whose fructose units are joined by glycosidic bonds, while insulin is a protein whose amino acids are joined by peptide bonds.

Question 3

Previous-year question
The two functional groups characteristic of sugars are [NEET 2018]
  1. hydroxyl and methyl
  2. carbonyl and methyl
  3. carbonyl and hydroxyl
  4. carbonyl and phosphate
Show answer
Answer: (C) carbonyl and hydroxyl
Explanation: Carbohydrates are polyhydroxy aldehydes or ketones, so they always carry a carbonyl group along with several hydroxyl groups.

Question 4

Previous-year question
Which one of the following statements is wrong? [NEET 2016]
  1. Sucrose is a disaccharide
  2. Cellulose is a polysaccharide
  3. Uracil is a pyrimidine
  4. Glycine is a sulphur containing amino acid
Show answer
Answer: (D) Glycine is a sulphur containing amino acid
Explanation: Glycine has only a hydrogen atom as its side chain and contains no sulphur; the sulphur-containing amino acids are cysteine and methionine.

Question 5

Previous-year question
Which one of the following is a non-reducing carbohydrate? [AIPMT 2014]
  1. Maltose
  2. Sucrose
  3. Lactose
  4. Ribose 5-phosphate
Show answer
Answer: (B) Sucrose
Explanation: In sucrose the reducing groups of glucose and fructose are both involved in the glycosidic linkage, so no free aldehyde or ketone group remains and the sugar is non-reducing.

Question 6

Previous-year question
Which of the following is a reducing sugar? [AIPMT 2002]
  1. Galactose
  2. Gluconic acid
  3. β-methyl galactoside
  4. Sucrose
Show answer
Answer: (A) Galactose
Explanation: Glucose, fructose, mannose and galactose are hexose monosaccharides that possess a free aldehyde or ketone group. This group can reduce Cu²⁺ to Cu⁺, so these sugars are called reducing sugars.

Question 7

Previous-year question
The most abundant organic compound on earth is [AIPMT 2004]
  1. Protein
  2. Cellulose
  3. Lipids
  4. Steroids
Show answer
Answer: (B) Cellulose
Explanation: Cellulose is a fibrous polysaccharide that forms the structural component of the plant cell wall and also occurs in some primitive fungi and in the tunic of ascidians. Since plant material is so abundant, cellulose is the most abundant organic substance on earth, although it can be digested by only a few microbes present in the gut of ruminants and termites.
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Question 8

Previous-year question
Carbohydrates, the most abundant biomolecules on earth, are produced by [AIPMT 2005]
  1. Some bacteria, algae and green plant cells
  2. Fungi, algae and green plant cells
  3. All bacteria, fungi and algae
  4. Viruses, fungi and bacteria
Show answer
Answer: (A) Some bacteria, algae and green plant cells
Explanation: Carbohydrates are organic compounds synthesised during photosynthesis in the chlorophyll-containing cells of some bacteria, algae and green plants. Fungi and viruses are not photosynthetic and therefore cannot produce them in this way.

Question 9

Previous-year question
The macromolecule chitin is a [NEET 2013]
  1. Nitrogen-containing polysaccharide
  2. Phosphorus-containing polysaccharide
  3. Sulphur-containing polysaccharide
  4. Simple polysaccharide
Show answer
Answer: (A) Nitrogen-containing polysaccharide
Explanation: Chitin is a complex homopolysaccharide built of N-acetylglucosamine units, an amino sugar derived from glucose. Because each unit carries nitrogen, chitin is a nitrogen-containing polysaccharide.

Question 10

Previous-year question
Which one of the following is a non-reducing carbohydrate? [AIPMT 2014]
  1. Maltose
  2. Sucrose
  3. Lactose
  4. Ribose 5-phosphate
Show answer
Answer: (B) Sucrose
Explanation: Sucrose is a disaccharide of glucose and fructose in which both anomeric carbons are involved in the glycosidic linkage, so no free anomeric carbon remains and it is non-reducing. Maltose, lactose and ribose 5-phosphate all retain a free ketonic or aldehydic group and are therefore reducing.

Question 11

Previous-year question
The chitinous exoskeleton of arthropods is formed by the polymerisation of [AIPMT 2015]
  1. Keratin sulphate and chondroitin sulphate
  2. D-glucosamine
  3. N-acetyl glucosamine
  4. Lipoglycans
Show answer
Answer: (C) N-acetyl glucosamine
Explanation: Chitin is formed by the polymerisation of N-acetyl glucosamine, a derivative of glucose. Besides forming the arthropod exoskeleton, it is a characteristic component of the fungal cell wall, of the radula of molluscs and of the beaks and internal shells of cephalopods.

Question 12

Previous-year question
Which two functional groups are characteristic of sugars? [NEET 2018]
  1. Carbonyl and phosphate
  2. Carbonyl and methyl
  3. Hydroxyl and methyl
  4. Carbonyl and hydroxyl
Show answer
Answer: (D) Carbonyl and hydroxyl
Explanation: Sugars are chemically carbohydrates and are polyhydroxy aldoses and ketoses. Aldoses bear a terminal aldehyde or —CHO group while ketoses have an internal ketone or —CO group, and both types carry several hydroxyl groups, so the two characteristic functional groups are carbonyl and hydroxyl.

Question 13

Previous-year question
A dehydration reaction links two glucose molecules to produce maltose. If the formula for glucose is C₆H₁₂O₆, then what is the formula for maltose? [NEET 2022]
  1. C₁₂H₂₄O₁₂
  2. C₁₂H₂₂O₁₁
  3. C₁₂H₂₄O₁₁
  4. C₁₂H₂₀O₁₀
Show answer
Answer: (B) C₁₂H₂₂O₁₁
Explanation: In a dehydration or condensation reaction one molecule of water is removed when the two monomers are joined. Two glucose molecules give C₁₂H₂₄O₁₂, and the loss of H₂O leaves C₁₂H₂₂O₁₁, which is the molecular formula of maltose.

Question 14

Previous-year question
Cellulose does not form a blue colour with iodine because [NEET 2023]
  1. It is a helical molecule
  2. It does not contain complex helices and hence cannot hold iodine molecules
  3. It breaks down when iodine reacts with it
  4. It is a disaccharide
Show answer
Answer: (B) It does not contain complex helices and hence cannot hold iodine molecules
Explanation: Starch gives a blue-black colour because the helical structure of its amylose fraction traps iodine molecules to form an iodine-amylose complex. Cellulose lacks such helices and its chains are tightly packed and rigid, so iodine molecules cannot penetrate to form a complex.

Question 15

Previous-year question
Pyrenoids are made up of [1995]
  1. a core of starch surrounded by a sheath of protein
  2. a proteinaceous centre with a starchy sheath
  3. a core of nucleic acid surrounded by a protein sheath
  4. a core of protein surrounded by a fatty sheath
Show answer
Answer: (B) a proteinaceous centre with a starchy sheath
Explanation: A pyrenoid consists of a dense central body of protein, largely the carbon-fixing enzyme RuBisCO, surrounded by a shell of starch. It lies within the chloroplast of many algae and is the site at which photosynthetically fixed carbon is converted into stored starch.

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