What are macromolecules? Give examples.
Macromolecules are biomolecules found in the acid insoluble fraction of living tissues. They have molecular weights in the range of ten thousand daltons and above. Macromolecules are also called biomacromolecules and are polymers made of different building blocks.
Only three types of macromolecules are found in living systems: proteins, nucleic acids (RNA and DNA), and polysaccharides. Proteins are heteropolymers made of amino acids, nucleic acids are composed of nucleotides, and polysaccharides are long chains of sugars. Although lipids are found in the acid insoluble fraction due to their association with membranes, they are not strictly macromolecules.
Explanation
The textbook clearly defines macromolecules based on their molecular weight (ten thousand daltons and above) and their presence in the acid insoluble fraction. The three true macromolecules are proteins, nucleic acids, and polysaccharides. Lipids are mentioned separately as they appear in the macromolecular fraction only due to membrane association, but are not strictly macromolecules. Students should note this distinction as it is frequently tested.