Final answer:
A macromolecule is a large molecule made from linking smaller subunits called monomers. Proteins, a class of biological macromolecules, consist of amino acids that combine to form complex structures essential for life functions. The correct answer is A) A large molecule with smaller subunits.
Step-by-step explanation:
A macromolecule is a large molecule typically formed by the polymerization of smaller subunits called monomers. When we're writing a paragraph about protein macromolecules, we'd be referring to a specific type of biological macromolecule. Proteins are one of the four major classes of biological macromolecules, alongside nucleic acids, carbohydrates, and lipids. These biological macromolecules are essential for life and perform a myriad of functions within cells. They are made up of smaller organic molecules and contain carbon, which forms covalent bonds allowing the construction of complex structures. In the case of proteins, their monomers are amino acids, which combine to form polymers through dehydration synthesis, where water is released.
Thus, the correct answer to the question 'What is a macromolecule?' is A) A large molecule with smaller subunits, as macromolecules are formed by monomers linking together to create large, complex structures.