Question

3. Draw the triacylglyceride formed from glycerol and three molecules of oleic acid. 4. The melting point of stearic acid is 70°C, and the melting point of oleic acid is 4°C. Explain in detail why their melting points are so different.

Answer 1

Ans-3:

The reaction with glycerol with oleic acid and product structure is given below:

m H₂ c-oh HC-01 + 3.0m Hic -OH glycerol oleic Acid 1-3420 che comwa chouw becomwww Glyceride

Ans-4:

Stearic has a melting point of 70 ºC whereas Oleic acid has melting point of 4 ºC.

This difference in m.p. is mainly due to the presence of one double bond in the oleic acid molecule where as in stearic acid no double bond is present, though both have same chain length of 18 carbons. The presence of double bond in oleic acid makes the molecule bent in its structure compared to the linear structure of stearic acid, rendering less intermolecular forces and hydrogen bonding in oleic acid. This results in less energy to break the inter-molecular forces and bring the molecules into the molten state easily, therby showing the low m.p.

$1585592290059_blob.png$

Oleic Acid, m.p. = 4 ºC.

O

Stearic Acid, m.p. 70 ºC.

Ans-5:

In proteins, the primary structure is of the amino acid sequence. Secondary structure is the local interactions between polypeptide chains and includes α-helix and β-pleated sheet structures. Tertiary structure is the overall the 3D folding affected by the interactions between R groups.

The tertiarry 3D structure generally affected by denaturation.

Ans-6: The dipeptide structure is as follows:

N ( ) * 4| || || || * || col3 glycine alanine NHy - chyl-NH- ch-C-04 CH3 • Rectangular Snip clipeptide