Can anyone tell me a balanced chemical equation to show how two serine molecules react together to form an amide bond ?

Serine is HO2CCH(NH2)CH2OH

see Serine - Wikipedia, the free encyclopedia

one end of the serine molecule is a carboxylic acid R-COOH (or RCO2H) The other part of a serine molecule is an amine - R-NH2.

R-CO2H + R-NH2 = R-CO---NR + H2O (the "---" represents the amide bond.)

Water is a co-product of the reaction.

To balance it, write two serine molecules going to one amide-joined molecule + water.