Question

From your results, rank the standard lipids by increasing order of polarity for each of the two chromatographic conditions that were assessed. Include the chemical structures of all lipids standards and, for each one, identify the polar groups. For each pair of standards, compare the polarity ranking within members of the pair. Explain your reasoning.  

Pair 1: FA (fatty acid) & PC (phosphatidylcholine)

Pair 2:  PI (phosphatidylinositol) & PE (phosphatidylethanolamine)

Pair 3: CL (cardiolipin) & CH (cholesterol)

CS / CHO O O PL FA PE T PC CH FAO Oa OPE OPE PC PI Jpc OPI

Answer 1

Pair 1 :

La CH(CH2) 5 (CH2),coon NET fatty acid 0- Phosphatidyl choline

Presence of phosphate group ( in hydrophilic head ) in phospholipid ( here, phosphatidyl choline ) makes it more polar than fatty acid.

Pair 2

phosphatidyl inositol

НАС H₃ca o -p-ona HOL о-р-ОН он

Phosphatidyl ethanolamine

CH2-0-C-R1 R2-2-0-C-H CH2-O-P-O-CH2CH2NH2 OH R1, R2 = fatty acid residues

Presence of more phosphate group makes it more polar hence phosphatidylethanolamine is more polar than phosphatidylinositol.

PART 3

Cardiolipin

o-P-0-CH2-CH-CH2-O-P-O R1-0-0-CH R2-4-0-CH2 HC-0–2-RS H2C0-c-R

Cholestrol

24 21 12 19 22 20 25 26 23 27 Ho HC cholest-5-en-3-ol cholest-5-en-35-01

Cardiolipin is more polar than cholestrol because of its phosphate group and high concentration of ester oxygen.