Final answer:
The correct answer is d) starch, which is a polysaccharide and not a lipid. Lipids are insoluble in water and include substances like fats, oils, waxes, and steroids such as cholesterol. Phospholipids and waxes are examples of lipids that make up cell membranes and the waxy coating on feathers.
Step-by-step explanation:
The student's question is asking to identify which of the given options is not an example of a lipid. The options provided are earwax, cholesterol, cell membrane, and starch. Lipids are a diverse group of compounds that are insoluble in water and include fats, oils, waxes, and certain vitamins and hormones. Some common examples include margarine (a type of fat), waxes such as those coating animal feathers, and phospholipids, which make up the cell membrane.
Cholesterol is a steroid and is also categorized as a lipid because it is part of cell membranes and involved in various biological processes, such as the production of bile salts and hormones. Phospholipids, such as phosphatidylserine and phosphatidylcholine, are major components of the plasma membrane of cells. Wax is also a lipid; earwax and the waxy covering on leaves are examples.
However, starch is not a lipid — it is a polysaccharide, which is a carbohydrate composed of many glucose units. Polysaccharides like cellulose and starch are large carbohydrate molecules that serve as energy reserves and structural components in plants. Hence, the correct answer to the student's question is d) starch, as it is not an example of a lipid.