The Chemistry of Biology Practice Test

Proteins are the most common organic molecules in a cell because they carry out the majority of the cell’s essential functions. Cells rely on a vast and diverse set of proteins to perform tasks such as speeding up chemical reactions (enzymes), providing structural support (cytoskeleton and used in tissues), enabling transport across membranes, sending and receiving signals, and defending against stress and pathogens. This huge demand for functional versatility means proteins are produced in large quantities and come in many different forms, more so than the other major classes of organic molecules.

Nucleic acids are crucial for storing and transmitting genetic information, lipids form membranes and store energy, and carbohydrates provide energy storage and some structural roles, but their overall abundance and variety are typically less than that of proteins. Hence, proteins are the most common organic molecules in a cell.