Lecithin, a small molecular weight organic compound found in living tissues, is an example of:

The correct option is Phospholipids.

Step-by-step Explanation:

1. Understanding Lecithin:
Lecithin is a generic term to designate any group of yellow-brownish fatty substances occurring in animal and plant tissues. Chemically, it refers specifically to phosphatidylcholine.

2. Structure of Lecithin:
Lecithin is composed of phosphoric acid, cholines, esters of glycerol, and two fatty acids. Since it contains a phosphate group attached to a lipid (glycerol esterified with fatty acids), it belongs to the class of compound lipids called phospholipids.

3. Evaluating the Options:
- Amino acids: These are the building blocks of proteins, containing amine and carboxyl functional groups. Lecithin is not a protein precursor.
- Phospholipids: These are amphiphilic lipids containing a phosphate group. Lecithin is a classic example of a phospholipid (specifically, a glycerophospholipid).
- Glycerides: While lecithin contains a glycerol backbone, the presence of the phosphate group and choline makes it specifically a phospholipid, not a simple glyceride (like mono-, di-, or triglycerides).
- Carbohydrates: These are organic compounds consisting of carbon, hydrogen, and oxygen, typically with a hydrogen-oxygen atom ratio of 2:1 (sugars, starches, cellulose). Lecithin is a lipid, not a carbohydrate.

Therefore, lecithin is an example of a phospholipid.