Lipid come under acid insoluble fraction during analysis of chemical composition of tissues. Why?

Options

A. It has low molecular weight
B. It has high molecular weight
C. It is polymer
D. On grinding, the biomembranes are broken into pieces and form insoluble vesicles

Answer

### Step-by-Step Solution:

1. **Understanding the Analysis Process**: When analyzing the chemical composition of tissues, a common method involves grinding the tissue in a solvent, such as trichloroacetic acid. This process helps to separate the components of the tissue into different fractions.

2. **Separation of Fractions**: After grinding the tissue, the mixture is strained to separate it into two main fractions: the acid-soluble fraction and the acid-insoluble fraction.

3. **Role of Lipids**: Lipids are a major component of cell membranes. When the tissue is ground, the cell membranes, which are primarily composed of lipids, are disrupted.

4. **Formation of Vesicles**: The disruption of the cell membrane leads to the formation of vesicles. These vesicles are structures that encapsulate lipids and other membrane components.

5. **Insolubility of Vesicles**: The vesicles formed from the broken cell membranes are insoluble in water. This means that they do not dissolve in the solvent used for the analysis (trichloroacetic acid).

6. **Conclusion**: Since the lipids are contained within these insoluble vesicles, they are classified under the acid-insoluble fraction during the analysis of the chemical composition of tissues.

### Final Answer:
Lipid comes under the acid-insoluble fraction during the analysis of chemical composition of tissues because, upon grinding the tissue, the cell membranes break down and form vesicles that are insoluble in water.

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