Question

1. What are some roles played by lipids in a cell?
2. What is the role of chloroform in a lipid extraction? Is chloroform more or less dense than water?
3. What are a single-phase (monophasic) solution and a biphasic solution? How are those related to lipid extraction?

Answer 1

The four most important roles played by lipids in a cell are the following:-

(1) storage of energy, their mobilisation and finally usage.

(2) Form membranes of the cell and important organelles, hence providing structural support

(3) Function as chemical messengers and take part in signalling

(4) Provide thermal and electrical insulation.

Lipids that are associated hydrophobically in the cells are extracted using non-polar solvents, since, such lipids are soluble in nonpolar solvents. Chloroform is one such non-polar solvent. Similarly, the extraction could also happen with other non polar solvents such as benezene or ethyl ether.

Chloroform is more dense than water. Its density is 1.48 g/mL while that of water is 1.00 g/ml.

Biphasic solution is a sytem where two immiscible phases are brought in contact in an aqueous system unlike monophasic solution where there is only a single phase.

In the process of lipid extraction, the tissue homogeneate contining lipids is mixed with chloroform and methanol in a 1:2 ratio v/v. This is an example of biphasic mixture. Here, the chloroform layer contains lipid and methanolic layer contains the non-lipids. Finally, the lipids are extracted from the chloroform layer.