Textbook Problem

What is the basis for deciding if a substance is a lipid?

Interpretation Introduction

Interpretation:

The basis for the decision that a substance is a lipid is to be stated.

Concept introduction:

Lipids are organic compounds which are fatty acids or the derivatives of fatty acids. They are insoluble in water but are soluble in non-polar organic solvents. They include natural oils, waxes, and steroids. Lipids are present in the cell membrane of the living cell.

Answer to Problem 18.1E

When a biological substance is greasy, waxy, oily and insoluble in water, then the substance is considered as a lipid.

Explanation of Solution

Lipids are one of those macromolecular substances that are present in the living cell. Lipid composes the cell membrane of the living cell. The lipids have a greasy, waxy and oily texture. The lipids are insoluble in water. Therefore, it can be easily decided that a substance is a lipid or not by checking these characteristics of lipid.

Conclusion

When a biological substance is greasy, waxy, oily and insoluble in water, then the substance is considered as a lipid.