Final answer:
The enzyme that adds a phosphate group to target proteins in signal transduction pathways is c. kinase.
Step-by-step explanation:
In signal transduction pathways, kinases play a pivotal role by catalyzing the addition of phosphate groups to specific target proteins, a process known as phosphorylation. This modification serves as a molecular switch, regulating protein activity and transmitting signals within cells. Kinases transfer phosphate from ATP to target proteins, altering their conformation and function.
This dynamic regulation is crucial for diverse cellular processes, including growth, metabolism, and response to external stimuli. Dysregulation of kinase activity is implicated in various diseases, making kinases significant targets for therapeutic intervention, with pharmaceuticals designed to modulate their activity for medical purposes.