Hey good morning. How is everybody doing? So today we actually did some calculations in biochemistry. So thats to show you that it is not all about learning structures and memorizing enzymes ( although it seems that way sometimes). WE BIOCHEMIST KNOW HOW TO USE A CALCULATOR!
So we did the titration of glutamate. Its a pretty straight forward calculations but some of my friends were having problems as they did not have a chemistry back ground. So I am going to post the video and make some general comments.
So first of all we know that acids exsit below the pH 7 and alkaline exist above the pH 7. pH 7 is like neutral ground. 7 is also the pH of water. So some definitions are that Lewis acids are substance which are ionized and lose a proton while Lewis bases accepts a proton.
The general way of explaining these two definitions are the following two formulas:
HCl + H2O —–> H3O+ + Cl-
So in the above equation water was added to hydrochloric acid and the acid lost a proton (hydrogen) and the water accepted that proton. So water acts as a base.
NH3 + H2O —–> NH4+ + H2O ——>
So what happens here is that ammonia is acting as the base and water is acting as an acid. Ammonia accepts the proton while water donate the proton.
So basically what is happening in the titration is as pK increases the hydrogen is lost from different groups. Wheter it be the alpha amino group, R group or alpha carboxylic group.
When a proton (hydrogen) is lost from a neutral base the final product has a negative charge hence:
COOH —-> COO- + H+
When hydrogen is lost from a positive substance the product is neutral. Hence:
NH4+——> NH3 + H+
Concerning net charges now:
The net charge is basically the total charge on the amino acid. So COO- has a 1- charge. NH3 has 0 charge and NH4+ has 1+ charge. So lets say that the follwing groups were present on the amino acid:
alpha amino group: NH4+
alpha carboxylic group : COO-
R group: COO-
The net charge will be 1- (1+(-1)+(-1).
The final calculation is just the pI value (isoelectric point). For this you just take the pK values on the two sides of the amino acid which has a net charge of zero. You add up these two pK values and divde by 2. Isoeclectric point is the pH at which the amino acis has a net charge of zero.
So I hope my chemistry insight came in useful to some of you. Enjoy your day and please practice.