(d) Ketoheptose

(b) Anomeric hydroxyl group

(b) L - amino acid

(c) It cannot be synthesised by human body.

(c) Tertiary

(a) A - U base pairing

• (a) The structure of sucrose contains glycosidic linkage between C-1 of α-glucose and C-2 of β-fructose. Since the potential aldehyde and ketone groups of both the monosaccharide units are involved in the formation of the glycosidic bond (i.e., α, β-1,2- glycosidic bond), sucrose is a non-reducing sugar and gives negative Tollen's test.
• (b) The glycosidic bond in maltose is in between C-1 of one glucose ring and C-4 of the other (i.e., α-1,4-glycosidic linkage). The hemiacetal group at C-1 of the second ring is not involved in the glycosidic linkage. Hence, maltose is a reducing sugar and gives positive Tollen's test.

On complete hydrolysis DNA yields 2-deoxy-D-ribose, adenine, thymine, guanine, cystosine and phosphoric acid. Since adenine always forms two hydrogen bonds with thymine, the hydrolysis of DNA gives equimolar quantities of adenine and thymine.

• α-Amino acids have high melting points compared to the corresponding amines or carboxylic acids of comparable molecular mass due to the presence of both acidic (carboxylic group) and basic (amino group) groups in the same molecule.
• In aqueous solution, proton transfer from acidic group to amino (basic) group of amino acid forms a salt, which is a dipolar ion called zwitter ion.

Thus, a-amino acids have high melting points compared to the corresponding amines or carboxylic acids of comparable molecular mass.

• Sucrose is dextro rotatory. On hydrolysis it gives equimolar mixture of D-(+) glucose and D-(-) fructose. Since the laevorotation of fructose (-92.4°) is more than dextrorotation of glucose (+ 52.7°), the hydrolysis product has net laevorotation.
• Thus, hydrolysis of sucrose brings about a change in the sign of rotation, from dextro (+) to laevo (-) and the product is called as invert sugar and so the hydrolysis of sucrose is called inversion.

• Proteins when subjected to high temperature undergo disruption of noncovalent interactions which are responsible for the specific shape of protein. That is, it undergoes denaturation.
• Denaturation disturbs the specific structure of egg albumin which causes a change in the physical properties.

Thus, on boiling egg albumin becomes opaque white.

(a) The polynucleotide is double stranded. (DNA)

(b) The polynucleotide contains uracil. (RNA)

(c) The polynucleotide contains D-ribose (RNA).

(d) The polynucleotide contains Guanine (RNA, DNA).

(i) 5' - ACGTAC-3'

The complementary strand runs in opposite direction from the 3' end to the 5' end. It has the base sequence decided by complementary base pairs A - T and C - G.

(ii) DNA molecule : 5-CGTTTAAG-3'

The complementary strand runs in opposite direction from the 3’ end to the 5’ end. It has the base sequence decided by complementary base pairs A-T and C-G.

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

(i) Dipeptide from glycine :

Carboxylic group of glycine reacting with amino group another molecule of glycine to form dipeptide

(ii) Dipeptide from alanine :

Carboxylic group of alanine reacting with amino group of another molecule of alamine to form dipeptide.

(iii) Dipeptide from glycine and alanine :

Carboxylic group of glycine reacting with amino group another molecule of alanine to form dipeptide

(iv) Dipeptide formed from alanine and tyrosine :

(v) Dipeptide formed from glycine and tyrosine :

(i) Glucose reacts with hydroxyl amine in an aqueous solution to form glucose oxime. This indicates the presence of -CHO (formyl group) in glucose.

(ii) Glucose on oxidation with mild oxidising agent like bromine water gives gluconic acid which shows carbonyl group in glucose is aldehyde (formyl group) group.

(i) ∝-Helix : In ∝-helix structure, a polypeptide chain gets coiled by twisting into a right handed or clockwise spiral known as ∝-helix. The characteristic features of ∝-helical

(ii) β-Pleated sheet : The secondary structure is called β-pleated sheet when two or more polypeptide chains, called strands, line up side-by-side (Fig.)