JEE Chemistry Biomolecules MCQs Set 26

Answer: (a) Adenine, guanine and cytosine

Explanation:
1. DNA contains A, G, C and T; RNA contains A, G, C and U.
2. The three common ones are A, G and C.

Teacher's Note:
1. Recall the standard fact.
2. DNA contains A, G, C and T; RNA contains A, G, C and U.

Answer: (c) Thymine

Explanation:
1. DNA contains thymine in place of uracil.

Teacher's Note:
1. Recall the standard fact.
2. DNA contains thymine in place of uracil.

Answer: (d) Peptide bonds

Explanation:
1. The carboxyl group of one amino acid condenses with the amino group of the next with loss of water, forming a peptide (amide) bond \( \ce{-CO-NH-} \).

Teacher's Note:
1. Recall the standard fact.
2. The carboxyl group of one amino acid condenses with the amino group of the next with loss of water, forming a peptide (amide) bond \( \ce{-CO-NH-} \).

Answer: (b) Vitamin B1

Explanation:
1. The fat-soluble vitamins are A, D, E and K.
2. B vitamins and C are water soluble and must be supplied regularly.

Teacher's Note:
1. Recall the standard fact.
2. The fat-soluble vitamins are A, D, E and K.

Answer: (a) Vitamin D

Explanation:
1. Vitamin D helps the absorption of calcium and phosphate for bone formation.

Teacher's Note:
1. Recall the standard fact.
2. Vitamin D helps the absorption of calcium and phosphate for bone formation.

Answer: (d) Thyroxine

Explanation:
1. Thyroxine is made in the thyroid gland from tyrosine.
2. Its deficiency causes goitre.

Teacher's Note:
1. Recall the standard fact.
2. Thyroxine is made in the thyroid gland from tyrosine.

Answer: (a) C1 of alpha-D-glucose to C2 of beta-D-fructose

Explanation:
1. Both reducing groups (the anomeric carbons) are used in the bond.
2. Hence sucrose is a non-reducing sugar.

Teacher's Note:
1. Recall the standard fact.
2. Both reducing groups (the anomeric carbons) are used in the bond.

Answer: (c) Glucose and galactose

Explanation:
1. Lactose, the milk sugar, is a beta-galactoside of glucose.

Teacher's Note:
1. Recall the standard fact.
2. Lactose, the milk sugar, is a beta-galactoside of glucose.

Answer: (d) \( \ce{-NH3+} \) and \( \ce{-COO-} \)

Explanation:
1. The acidic group gives a proton to the basic amino group within the molecule.
2. This internal salt is why amino acids have high melting points and dissolve in water.

Teacher's Note:
1. Recall the standard fact.
2. The acidic group gives a proton to the basic amino group within the molecule.

Answer: (b) D-ribose

Explanation:
1. RNA has ribose (OH at C2).
2. DNA has 2-deoxyribose.

Teacher's Note:
1. Recall the standard fact.
2. RNA has ribose (OH at C2).

Answer: (a) Sucrose

Explanation:
1. In sucrose both anomeric carbons are involved in the glycosidic bond, so no free aldehyde or hemiacetal group is left.
2. The others have a free anomeric carbon and reduce Fehling solution.

Teacher's Note:
1. Recall the standard fact.
2. In sucrose both anomeric carbons are involved in the glycosidic bond, so no free aldehyde or hemiacetal group is left.

Answer: (c) Secondary and tertiary structure

Explanation:
1. Heat breaks hydrogen bonds and other weak interactions that hold the folding.
2. The peptide bonds and thus the sequence are not broken.

Teacher's Note:
1. Recall the standard fact.
2. Heat breaks hydrogen bonds and other weak interactions that hold the folding.

Answer: (d) An enzyme

Explanation:
1. Enzymes are proteins that speed up reactions in the living cell and are specific for a substrate.
2. For example invertase hydrolyses sucrose.

Teacher's Note:
1. Recall the standard fact.
2. Enzymes are proteins that speed up reactions in the living cell and are specific for a substrate.