5. Which of the following is (are) an advantage(s) of protein phosphorylation in regards to biochemical signaling? I. Phosphorylation is rapid and specific. II. Phosphorylation is enzymatically reversible. III. Phosphorylation can be amplified by cascade systems. IV. Phosphorylation results in covalent modification of enzymes. A) I, II, III, IV

Protein Phosphorylation is one of the post -translated processes carried out to modify the translated protein either by activating or deactivating it, with conveniently bonding of inorganic phosphate ion to it. The reaction is reversible,with the forward reaction catalysed by enzyme Kinase, and the backward reaction catalysed by Phophatases.

It is important in regulation of many biochemical activities in the cells and regulation of cellular transport mechanisms.e,g Na+/K+ ATPase for ions transports.

Phosphorylation usually changed the polarity of amino acid residues by replacing the hydrophobic -R group of protein with the polar phosphate groups. The protein thus become activated This increases its hydrophilic properties needed for cell signalling transduction .

However,dephosphorylation(removal of the phosphate group) removes the hydrophilic effects and signalling properties.

Thus all the above options are related to phosphorylation of protein.