AP BIOLOGY

Detailed explanation-1: -The phosphorylation of a protein can make it active or inactive. Phosphorylation can either activate a protein (orange) or inactivate it (green). Kinase is an enzyme that phosphorylates proteins. Phosphatase is an enzyme that dephosphorylates proteins, effectively undoing the action of kinase.

Detailed explanation-2: -Phosphorylation provides a sensitive and dynamic way to regulate protein activity, stability, protein interaction and sub-cellular localization. Global regulators are often targeted by more than one kinase, altering the expression of many genes.

Detailed explanation-3: -Phosphorylation does sometimes inactivate proteins. For example, phosphorylation of the prokaryotic citric acid cycle enzyme isocitrate dehydrogenase blocks the enzyme’s active site (Hurley et al., 1990; Hurley et al., 1989), providing a rapid and reversible off-switch for the protein.

Detailed explanation-4: -Phosphorylation decreases the DNA binding ability of IL-4-stimulated STAT6, thereby inhibiting the transcription of STAT6-responsive genes. Inactivation of STAT6 by JNK-dependent Ser-707 phosphorylation may be one mechanism of controlling the balance between IL-1 and IL-4 signals.

Detailed explanation-5: -Phosphorylation is a reversible reaction. Most of the enzymes and receptors are activated and deactivated by phosphorylation and dephosphorylation (opposite of phosphorylation process), respectively. The phosphorylation of enzymes serves as a type of on/off switch, thus altering the specific activity or function.