chapter 14 Biomolecules Class 12 Chemistry Textbook Solution

1. Select the most correct choice.

i. CH2OH-CO-(CHOH)4-CH2OH is an example of
a. Aldohexose b. Aldoheptose
c. Ketotetrose d. Ketoheptose

ii. Open chain formula of glucose does not contain
a. Formyl group
b. Anomeric hydroxyl group
c. Primary hydroxyl group
d. Secondary hydroxyl group

iii. Which of the following does not apply to CH2NH2 – COOH
a. Neutral amino acid
b. L – amino acid
c. Exists as zwitter ion
d. Natural amino acid

iv. Tryptophan is called essential amino acid because
a. It contains aromatic nucleus.
b. It is present in all the human  proteins.
c. It cannot be synthesised by human body.
d. It is essential constituent of enzymes.

v. A disulfide link gives rise to the following structure of protein.
a. Primary
b. Secondary
c. Tertiary
d. Quaternary

vi. RNA has
a. A – U base pairing
b. P-S-P-S backbone
c. double helix
d. G – C base pairing

2. Give scientific reasons :

i. The disaccharide sucrose gives negative Tollens test while the disaccharide maltose gives positive Tollens test.

ii. On complete hydrolysis DNA gives equimolar quantities of adenine and thymine.

iii. α – Amino acids have high melting points compared to the corresponding amines or carboxylic acids of comparable molecular mass.

iv. Hydrolysis of sucrose is called inversion.

v. On boiling egg albumin becomes opaque white.

3. Answer the following

i. Some of the following statements apply to DNA only, some to RNA only and some to both. Lable them accordingly.
a. The polynucleotide is double stranded. ( ……..)
b. The polynucleotide contains uracil. ( ………)
c. The polynucleotide contains D-ribose (…….. ).
d. The polynucleotide contains Guanine (……… ).

ii. Write the sequence of the complementary strand for the following segments of a DNA molecule.
a. 5′ – CGTTTAAG – 3′

iii. Write the names and schematic representations of all the possible dipeptides formed from alanine, glycine and tyrosine.

iv. Give two evidences for presence of formyl group in glucose.

4. Draw a neat diagram for the following:
i. Haworth formula of glucopyranose
ii. Zwitter ion
iii. Haworth formula of maltose
iv. Secondary structure of protein
v. AMP
vi. dAMP
vii. One purine base from nucleic acid
viii. Enzyme catalysis