Final answer:
Proteins are the biomolecules in cells responsible for the array of functions a cell 'does,' including catalyzing biochemical reactions, providing structure, and regulating processes. They are distinct from other classes like carbohydrates, lipids, and nucleic acids, which serve their own crucial roles within the cell.
Step-by-step explanation:
The "do" molecules in cells that are responsible for the vast array of functions a cell performs are proteins. Proteins are one of the four major classes of biological macromolecules, alongside carbohydrates, lipids, and nucleic acids. Each of these macromolecule types plays a crucial role within the cell. However, when it comes to the functionality and actions within a cell, proteins are paramount. They catalyze biochemical reactions, provide structural support, regulate gene expression, and are involved in signaling pathways, among other tasks. The versatile structures of proteins allow them to interact with other molecules precisely and diversely, making them essential for the cell's activities and overall life.
While carbohydrates are primarily involved in energy storage and structural support, lipids make up cell membranes and store energy, and nucleic acids like DNA and RNA store and transmit genetic information, it is the proteins that execute most of the cellular functions.