AP BIOLOGY

Detailed explanation-1: -Protein kinases, also referred to as phosphotransferases, phosphorylate their target proteins in cells by attaching phosphates covalently to the side chains of serine, threonine or tyrosine residues.

Detailed explanation-2: -Protein kinases (PTKs) are enzymes that regulate the biological activity of proteins by phosphorylation of specific amino acids with ATP as the source of phosphate, thereby inducing a conformational change from an inactive to an active form of the protein.

Detailed explanation-3: -Activation is mediated by binding of cyclic AMP to the regulatory subunits, which causes the release of the catalytic subunits. cAPK is primarily a cytoplasmic protein, but upon activation it can migrate to the nucleus, where it phosphorylates proteins important for gene regulation.

Detailed explanation-4: -Protein kinases such as PKA and PKC catalyze the transfer of phosphate groups from ATP molecules to protein molecules.

Detailed explanation-5: -A protein kinase is a kinase which selectively modifies other proteins by covalently adding phosphates to them (phosphorylation) as opposed to kinases which modify lipids, carbohydrates, or other molecules.