The correct answer is D. None of these.
Proteins are large, complex molecules that are essential for life. They are made up of amino acids, which are linked together in a chain. The sequence of amino acids in a protein determines its structure and function. Proteins are found in all living things, and they perform a wide variety of essential functions, including:
- Building and repairing tissues
- Enzymes that catalyze chemical reactions
- Hormones that regulate body functions
- Antibodies that fight infection
Natural rubber is a polymer of isoprene, a type of terpene. It is a natural product that is found in the latex of many plants, including rubber trees. Starch is a polysaccharide that is made up of glucose units. It is a major source of energy for plants and animals. Cellulose is a polysaccharide that is made up of glucose units. It is the main structural component of plant cell walls.
None of these substances are proteins.