ive all along pronounced this test for protein as beu-rets test.
and today while i was at my course, i was wondering why the lecturer kept saying bi-urets test…. and was laughing at the pronunciation, until she explained why that test required NaOH to be added first and then followed by CuSO4…..
you see, the purplish/violet/lilac colouration that you see in a positive biuret’s test is because of the formation of this molecule known as uret. and this molecule comes in pairs. which is why its known as bi-uret.
so why add NaOH first and not the other way round?
because the for CuSO4 to react with the proteins present in the sample, you need an alkaline medium. so the NaOH is meant to create the necessary condition for the reaction.
you can still add CuSO4 first and then add in NaOH. but it’s just more right to prepare the condition first before adding the reagent needed for the reaction.
so there you go….
and then one of the guys sitting in my group laughed.
“tell this to my students and they’ll say, ‘ah ya la ya la… just tell us the steps can already lah…’ no need to waste my breath… just teach them how to do the steps and read results can already…”
i mean, i kind of agree with him to a certain extent. students need to be at a certain level of maturity to understand the concepts behind why certain things are done. though it doesnt mean im not going to try…. i’d probably tell my kids this rationale when they are in sec 4 when they can take in more abstract concepts. but tell this to sec 1s when they are learning food tests? its really not the time…..