[Campbell Biology P.271] In the context of the phosphorylation cascade depicted in Figure 11... | Practice Question

In the context of the phosphorylation cascade depicted in Figure 11.10, what are the primary opposing roles of protein kinases and protein phosphatases?

  • A: Protein kinases activate proteins by adding phosphate groups, while protein phosphatases inactivate proteins by removing phosphate groups.
  • B: Protein kinases produce ATP, while protein phosphatases consume ATP.
  • C: Protein kinases induce shape changes that decrease protein activity, while protein phosphatases increase it.
  • D: Protein kinases act as receptors for signaling molecules, while protein phosphatases relay the signal to the nucleus.

Explanation

The text explains: 'An enzyme that transfers phosphate groups from ATP to a protein is generally known as a protein kinase.' and 'Here, phosphorylation activates each protein, and dephosphorylation returns it to its inactive form.' Figure 11.10 also shows 'Protein phosphatases PP catalyze the removal of the phosphate groups from the proteins, making the proteins inactive again.' This clearly defines their opposing roles in protein activity regulation.