Which of the following biological macromolecules is usually not considered to be a polymer?

• A. Polysaccharides
• B. Nucleic acids
• C. Lipids
• D. Proteins

Answer: (C)

Verified step by step guidance

1. Step 1: Understand the definition of a polymer. A polymer is a large molecule composed of repeating subunits called monomers, which are covalently bonded together.
2. Step 2: Analyze each macromolecule option provided in the question. Polysaccharides, nucleic acids, and proteins are all composed of repeating monomer units (e.g., monosaccharides for polysaccharides, nucleotides for nucleic acids, and amino acids for proteins).
3. Step 3: Consider lipids. Lipids, such as fats and oils, are not composed of repeating monomer units. Instead, they are typically made up of glycerol and fatty acids, which are combined but do not form a polymer structure.
4. Step 4: Compare lipids to the other macromolecules. Unlike polysaccharides, nucleic acids, and proteins, lipids do not fit the definition of a polymer because they lack a repetitive chain of monomers.
5. Step 5: Conclude that lipids are usually not considered polymers, which aligns with the correct answer provided in the question.