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Multiple Choice
In protein regulation, which class of enzyme catalyzes the addition of a phosphate group to a substrate (phosphorylation)?
A
Aminoacyl-tRNA synthetase
B
DNA polymerase
C
Protein phosphatase
D
Protein kinase
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Verified step by step guidance
1
Understand the process of phosphorylation, which is the addition of a phosphate group (usually from ATP) to a substrate molecule, often a protein.
Recognize that enzymes catalyzing phosphorylation are called kinases, specifically protein kinases when the substrate is a protein.
Review the roles of the other enzymes listed: Aminoacyl-tRNA synthetase attaches amino acids to tRNA, DNA polymerase synthesizes DNA strands, and protein phosphatase removes phosphate groups (dephosphorylation).
Conclude that the enzyme class responsible for adding phosphate groups to proteins is protein kinase.
Summarize that protein kinases regulate protein function by phosphorylation, which is a key mechanism in cellular signaling and regulation.