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Biomolecules — NEET & JEE MCQs with answers
Living systems are made up of complex biomolecules such as carbohydrates, proteins, nucleic acids and lipids, while simple molecules such as vitamins and mineral salts also play an important role in the functions of organisms. Carbohydrates act mainly as energy sources and as storage or structural materials; proteins, polymers of α-amino acids, form the fundamental basis of structure and functions of life, and most enzymes, the biocatalysts, are proteins; nucleic acids are responsible for heredity; vitamins are accessory food factors whose deficiency causes specific diseases; and hormones act as intercellular messengers.
Topics in this chapter
- 10.1 Carbohydrates
- 10.2 Proteins
- 10.3 Enzymes
- 10.4 Vitamins
- 10.5 Nucleic Acids
- 10.6 Hormones
Free practice questions
Fructose is described in NCERT as an important:
- A. ketohexose
- B. aldohexose
- C. aldopentose
- D. ketotriose
Show answer
Answer: A — Option A is correct. The opening sentence of the sub-section calls fructose an important ketohexose — a six-carbon monosaccharide carrying a keto group. Glucose, by contrast, is the aldohexose of this chapter.
NCERT Class 12 Chemistry Part-2 · Ch 10 · §10.1.2.2 ("Fructose is an important ketohexose")
When the number of amino acids linked together is more than ten, the products are called:
- A. Hexapeptides
- B. Polypeptides
- C. Dipeptides
- D. Proteins
Show answer
Answer: B — The text says that when the number of such amino acids is more than ten, the products are called polypeptides, so option B is correct. The named short peptides stop at six, and 'protein' requires far more residues.
NCERT Class 12 Chemistry Part-2 · Ch 10 · §10.2.3 ("respectively. When the number of such amino acids is more than ten, then")
The letter 'e' was dropped from 'Vitamine' because later work showed that
- A. Most of them did not contain amino groups
- B. Most of them turned out to be acids
- C. Most of them were insoluble in water
- D. All chemical names had their 'e' removed
Show answer
Answer: A — Option A is correct. NCERT explains that most of these compounds were later found **not** to contain amino groups, so the final 'e' was dropped and the spelling 'vitamin' came into use. The change had nothing to do with solubility, with their being acids, or with any spelling reform of chemical names generally.
NCERT Class 12 Chemistry Part-2 · Ch 10 · §10.4 ("that most of them did not contain amino groups, so the letter 'e' was")
In the ladder analogy of the Watson box, each **rung** is composed of
- A. A phosphate and a deoxyribose unit
- B. Two amino acid residues
- C. A pair of purine or pyrimidine bases
- D. Two fatty acid chains
Show answer
Answer: C — Option C is correct. The box says the rungs are each composed of a pair of purine/pyrimidine bases. Phosphate and deoxyribose make up the rails, not the rungs, and neither amino acids nor fatty acids appear in the description.
NCERT Class 12 Chemistry Part-2 · Ch 10 · §10.5 biography box ("the rungs are each composed of a pair of purine/ pyrimidine bases. This")
Which one of the following statements does **not** agree with §10.3 of NCERT?
- A. Enzymes raise the magnitude of activation energy
- B. Enzymes are needed only in small quantities
- C. Enzymes are specific for a particular substrate
- D. An enzyme name generally ends in -ase
Show answer
Answer: A — Option A is correct as the statement that disagrees with the text. NCERT says enzymes reduce the magnitude of activation energy, so claiming they raise it is wrong. The other three — small quantities needed, specificity for a particular substrate, and the -ase ending — are each printed as written.
NCERT Class 12 Chemistry Part-2 · Ch 10 · §10.3 ("the magnitude of activation energy.")
The example NCERT chooses to illustrate the balancing function of hormones is
- A. The iodisation of table salt
- B. The development of sex characters
- C. Insulin keeping blood glucose in a narrow limit
- D. The identification of criminals by DNA
Show answer
Answer: C — Option C is correct. The text says 'The role of insulin in keeping the blood glucose level within the narrow limit is an example of this function.' Iodised salt, secondary sex characters and DNA fingerprinting are discussed later or in other sections and are not offered as this illustration.
NCERT Class 12 Chemistry Part-2 · Ch 10 · §10.6 ("the blood glucose level within the narrow limit is an example of this")
The ring formed in the cyclic structure of glucose is:
- A. four-membered
- B. seven-membered
- C. six-membered
- D. five-membered
Show answer
Answer: C — Option C is correct. NCERT states that glucose forms a six-membered ring, which is why the structure is called a pyranose structure. The five-membered ring belongs to fructose in its furanose form.
NCERT Class 12 Chemistry Part-2 · Ch 10 · §10.1.2.1 ("found that glucose forms a six-membered ring")
Glycine takes its name from the Greek word 'glykos' because glycine:
- A. Was first isolated from cheese
- B. Is the smallest of the amino acids
- C. Has a sweet taste
- D. Has a sweet smell in the solid state
Show answer
Answer: C — NCERT explains that glycine is so named since it has a sweet taste, glykos meaning sweet in Greek; hence option C. It was tyrosine, not glycine, that was first obtained from cheese.
NCERT Class 12 Chemistry Part-2 · Ch 10 · §10.2.1 ("its source. Glycine is so named since it has sweet taste (in Greek glykos")
NCERT's own word for the transmission of inherent characters from one generation to the next is
- A. Denaturation
- B. Heredity
- C. Hydrolysis
- D. Duplication
Show answer
Answer: B — Option B is correct. The text says this transmission of inherent characters is 'also called heredity'. Denaturation is a protein phenomenon, hydrolysis is a chemical breakdown, and duplication describes what a DNA molecule does during cell division.
NCERT Class 12 Chemistry Part-2 · Ch 10 · §10.5 ("called heredity. The particles in nucleus of the cell, responsible for")
The sources given in Table 10.3 for Vitamin $\mathrm{B_{12}}$ are
- A. Milk, eggwhite, liver and kidney
- B. Yeast, egg yolk, cereals and grams
- C. Wheat germ oil and sunflower oil
- D. Meat, fish, egg and curd
Show answer
Answer: D — Option D is correct. Row 5 lists meat, fish, egg and curd. Milk, eggwhite, liver and kidney belong to $\mathrm{B_2}$; yeast with egg yolk, cereals and grams to $\mathrm{B_6}$; and vegetable oils to Vitamin E.
NCERT Class 12 Chemistry Part-2 · Ch 10 · Table 10.3 ("Meat, fish, egg and")
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