Biomolecules Question 31
31. Lipids are insoluble in water because lipid molecules are
(a) hydrophilic
(b) hydrophobic
(c) neutral
(d) zwitter ions
Show Answer
Answer : b
Hints & Solutions
(b) Water attracting molecules are called hydrophilic. Water repelling molecules are called hydrophobic. Amino acids simultaneously carry positive and negative charges. Such substances are called zwitter ions. Lipids are compounds of $C, H, O$ but the ratio of $H$ and $O$ is more than 2: 1 , that is, the ratio of oxygen is lesser than carbohydrates. Lipids are insoluble in water but soluble in nonpolar solvents such as benzene, chloroform etc. The most common lipid found in a cell is phospholipid. It contains a hydrophilic (polar) head and a hydrophobic (non- polar tail).
32
(d)
Erucic acid is a monounsaturated omega-9 fatty acid, denoted $22: 1 \omega-9$. It is prevalent in rapeseed, wallflower seed, and mustard seed, making up 40 to 50 percent of their oils. Erucic acid is also known as cis-13-docosenoic acid and the trans isomer is known as brassidic acid.
