Final answer:
Carbon atoms form the backbone of macromolecules due to their ability to form four stable covalent bonds, enabling the formation of complex structures required for life such as proteins, nucleic acids, carbohydrates, and lipids.
Step-by-step explanation:
The backbone of large macromolecules is made of carbon atoms rather than hydrogen atoms because carbon has the unique ability to form stable covalent bonds with up to four different atoms. This versatility enables carbon to create complex and varied structures, including long chains, branching chains, and ring-shaped molecules, which are crucial for the diverse functions of biological macromolecules. Carbon's presence is essential for the structure and function of various macromolecules such as proteins, nucleic acids (DNA and RNA), carbohydrates, and lipids, which are all vital for life.
Moreover, carbon atoms can readily form larger, more complex molecules by bonding with other carbon atoms or other elements like nitrogen, oxygen, and phosphorus, adding to the structural diversity necessary for biological functions. The organic compounds thus formed often consist of monomers linked together to form polymers, providing the necessary complexity and specialization required for life processes.