The side chain of has a pka in the physiological ph range and is therefore often involved in proton transfer during enzymatic catalysis. the side chain of has a pka in the physiological ph range and is therefore often involved in proton transfer during enzymatic catalysis. his glu asp arg

Histidine (his)

Explanation:

Histidine (his), Arginine (arg), Aspartic acic (asp) and Glutamic acid (glu) have 3 acidic hidrogens each one, but only his has one physiological in the pH range.

the enthalpy of formation of water is given as -285.8kj/mol, which states that the enthalpy of formation is negative.

negative enthalpy of formation indicates that the heat is released during the reaction process. the heat is released from reaction to the surroundings the enthalpy is expressed with a negative sign with the energy given out in the reaction process.

the formation of water takes place by giving out heat which is -285.8 kj/mol.