Final answer:
The four major classes of macromolecules in living organisms are proteins, carbohydrates, lipids, and nucleic acids, each performing essential functions within the cell.
Step-by-step explanation:
The Four Major Classes of Macromolecules
The four major classes of macromolecules found in living organisms are proteins, carbohydrates, lipids, and nucleic acids. These organic compounds are essential for life, constructing a large part of cells and performing a variety of critical functions. Proteins act as cellular workhorses, facilitating biological reactions, forming cellular structures, and regulating cellular activity. Carbohydrates are vital for energy storage and supply, as well as providing structural support to cells. Lipids make up cell membranes, store energy, and act as signaling molecules. Finally, nucleic acids, which include DNA and RNA, carry genetic information and are involved in gene expression and regulation. These macromolecules are built of smaller units called monomers that join together to form polymers through dehydration reactions, and break down into monomers via hydrolysis.