Advanced Placement (AP) Biology Practice Exam

What effect do protein phosphatases have on proteins?

1. They phosphorylate proteins

2. They activate signal transduction pathways

3. They dephosphorylate proteins

4. They initiate local signaling processes

The correct answer is: They dephosphorylate proteins

Protein phosphatases play a crucial role in cellular regulation by removing phosphate groups from proteins, a process known as dephosphorylation. This activity predominantly impacts the function and activity of various proteins within the cell. When a protein is phosphorylated, it can undergo significant changes in shape and function, often leading to the activation of that protein or a change in its interaction with other molecules. By removing these phosphate groups, protein phosphatases can effectively inactivate proteins or revert them to their original state. This balance of phosphorylation and dephosphorylation controlled by kinases and phosphatases is essential for regulating various cellular processes, including signal transduction, cell cycle progression, and metabolic pathways.