Question

Cell membrane involves Sphingomyelin, Phosphatidylcholine, Phosphatidylethanolamine and Cholesterol, but butter does not involve these lipids. What lipids are involved in both cell membrane and butter?

There are Rf of some lipids. Please identify these unidentified lipids.

Standards	Rf
Sphingomyelin (SM)	0.0488
Phosphatidylcholine (PC)	0.0915
Phosphatidylethanolamine (PE)	0.2866
Cholesterol (C)	0.5183
Palmitic acid (PA)	0.5915

Blood			Egg Yolk			Butter
Rf	Identity		Rf	Identity		Rf	Identity
0.0549	SM		0.0549	SM		0.6402	unidentified
0.1159	PC		0.0793	PC		0.6829	unidentified
0.3110	PE		0.2744	PE
0.5305	C		0.5122	C
0.6646	unidentified		0.6646	unidentified
0.7073	unidentified

Answer 1

Cell membrane involves Sphingomyelin, Phosphatidylcholine, Phosphatidylethanolamine and Cholesterol, but butter does not involve these lipids.

Butter is about 80% fat, and the rest is mostly water.

It is very high in saturated fatty acids (about 70%) and holds a fair amount of monounsaturated fatty acids (about 25%). Polyunsaturated fats are only present in minimal amounts, consisting of about 2.3% of the total fat content.

Other types of fatty substances found in butter include cholesterol and phospholipids.

Around 11% of the saturated fats in butter are short-chainfatty acids (SCFAs), the most common of which is butyric acid.

Butter is the richest dietary source of dairy trans fats, the most common of which are vaccenic acid and conjugated linoleic acid (CLA).

So lipids which are involved in both cell membrane and butter are:-

• Cholesterol
• Phospholipids like Phosphatidylethanolamine, phosphatidylcholine
• Vaccenic acid
• Conjugated linoleic acid

It is difficult to determine the Rf values because the solvent front is not given in the question

Unidentified lipid with Rf value of 0.6646 can be triacylglycerol.