Final answer:
Proteins are the most diverse and versatile class of macromolecules, serving numerous functions in living organisms and constituting more than 50% of a cell's dry mass.
Step-by-step explanation:
The most diverse and versatile class of macromolecules in biological systems is proteins. Proteins play a plethora of roles within living organisms, including serving as enzymes, structural components, transporters, and more. They are polymers comprised of amino acids that are linked together in a linear sequence. The diversity of proteins is vast because each protein has a unique arrangement of amino acids, leading to different shapes and functions. Proteins are crucial to almost every function within a cell and can be found in large quantities, making up over 50% of the cell's dry mass. Understanding proteins is key to grasping how cells function and how various physiological processes are carried out.