Advanced Placement (AP) Biology Practice Exam

What type of pathway is characterized by the transfer of phosphate groups from ATP to substrate proteins?

1. G-protein linked receptor pathway

2. Tyrosine kinase receptor pathway

3. Ion channel receptor pathway

4. Steroid hormone signaling pathway

The correct answer is: Tyrosine kinase receptor pathway

The pathway characterized by the transfer of phosphate groups from ATP to substrate proteins is known as the tyrosine kinase receptor pathway. This type of signaling pathway involves receptor proteins that, upon binding a ligand (such as a growth factor), undergo autophosphorylation on tyrosine residues. This phosphorylation facilitates the recruitment and activation of downstream signaling molecules, leading to a cascade of cellular responses. The addition of phosphate groups from ATP to specific tyrosine residues on these proteins changes their conformation and activity, enabling the propagation of the signal within the cell. This pathway is crucial in regulating various cellular processes, including cell growth, differentiation, and metabolism, and the dysregulation of tyrosine kinase activity is often associated with cancers and other diseases. The ability of these receptor tyrosine kinases to alter protein function through phosphorylation makes this pathway a key player in many biological responses.