AP BIOLOGY

Detailed explanation-1: -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-2: -The protein kinases belong to the great family of kinases and are responsible for the mechanism of phosphorylation. They are activated by phosphorylation which in turn activates a cascade of events leading to the phosphorylation of different amino acids (3).

Detailed explanation-3: -Protein kinases can add phosphate groups to serine, threonine, and tyrosine residues on histone tails and occasionally, other regions of the histone, resulting in histone phosphorylation (reviewed in Bannister and Kouzarides, 2011; reviewed in Rossetto et al., 2012).

Detailed explanation-4: -The addition of a phosphate (PO43 −) group is often used as a major homeostatic control. In many proteins and enzymes, phosphorylation serves as a type of ‘on/off’ switch, thereby altering function or activity. Enzymes designated as kinases usually catalyze phosphorylation reactions using ATP as a cosubstrate.

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.