Which of the following is not a macromolecule?

Options

A. Protein
B. Lipid
C. Nucleic acid
D. polysaccharide

Explanation

To determine which of the following is not a macromolecule, we need to analyze each option provided:

1. **Protein**: Proteins are macromolecules made up of long chains of amino acids. These amino acids are the monomers that link together to form the polymer known as protein. Therefore, proteins are considered macromolecules.

2. **Lipid**: Lipids are not classified as macromolecules because they are not polymers. While they are large molecules, they do not consist of repeating monomer units like proteins, nucleic acids, or polysaccharides. Instead, lipids are composed of glycerol and fatty acids, which do not form long chains of repeating units. Hence, lipids are not macromolecules.

3. **Nucleic Acid**: Nucleic acids, such as DNA and RNA, are macromolecules made up of long chains of nucleotides. The nucleotides serve as the monomers that link together to form the polymer structure of nucleic acids. Thus, nucleic acids are indeed macromolecules.

4. **Polysaccharide**: Polysaccharides are also macromolecules, consisting of long chains of monosaccharides (the monomers). Examples include starch and cellulose, which are formed by the polymerization of sugar units. Therefore, polysaccharides are considered macromolecules.

After analyzing all the options, we conclude that the only option that is not a macromolecule is **lipid** (option 2).

**Final Answer**: Lipid (option 2) is not a macromolecule.