Protein kinase is an enzyme that ________.
A) functions as a second messenger molecule
B) serves as a receptor for various signal molecules
C) activates or inactivates other proteins by adding a phosphate group to them
D) produces second messenger molecules

Question

Quizplus · Accepted Answer

Protein kinase adds a phosphate group to other proteins, which can activate or inactivate them, making it an enzyme involved in signaling pathways. Choices A, B, and D are incorrect as they describe other types of signaling molecules or receptors.

Protein Kinase Is an Enzyme That ________