Introduction / Context:
General biology questions often ask you to distinguish among major biomolecule classes: proteins (polymers of amino acids), polysaccharides (polymers of sugars), nucleic acids, and various natural polymers. Correct classification avoids common mix-ups when options list familiar everyday materials that are not proteins at all.
Given Data / Assumptions:
- Natural rubber is a polyisoprene elastomer (not a biopolymer of amino acids).
- Starch and cellulose are polysaccharides derived from glucose monomers.
- No explicit protein (e.g., albumin, casein, keratin) appears in the options.
Concept / Approach:
Proteins consist of amino acids linked by peptide bonds and typically contain nitrogen in characteristic amide linkages. By contrast, starch (amylose/amylopectin), cellulose, and glycogen are carbohydrates built from glucose units linked by glycosidic bonds. Natural rubber is an unsaturated hydrocarbon polymer (cis-1,4-polyisoprene). Therefore, none of the listed substances is a protein, and the correct answer is “None of these.”
Step-by-Step Solution:
Check each option’s class: rubber → elastomer; starch/cellulose/glycogen → polysaccharides.Recall defining feature of proteins: amino acid composition and peptide bonds.Since no protein is present, choose “None of these.”Verify there is no trick option that names a known protein (there is not).
Verification / Alternative check:
Examples of proteins: hemoglobin, insulin, albumin, casein. None appear among the options, confirming the selection.
Why Other Options Are Wrong:
Natural rubber: Hydrocarbon polymer, not a peptide.Starch / Cellulose / Glycogen: Carbohydrates (polysaccharides), not proteins.
Common Pitfalls:
Associating “natural” with “protein.” Natural origin does not determine biomolecular class; structural chemistry does.
Final Answer:
None of these
Discussion & Comments