Thank you so much! The trick you taught is a true game-changer!

This is awesome! Thank you!

Phenomenal work & great teaching methods. Way to simplify the concept!!👍

I've said it before and I'll say it again, this channel is criminally underrated. "Professors HATE this one simple trick!" (watching Science Simplified videos...)

after many years, I have finally understood the isoelectric point concept 😭thank you very much

You are amazing. Thank you so much.

Im lost do we have t know all functional group pkas??????????

Im very confused, howd you know the pkas were 2 and 4 for those carboxyl

@sciencesimplified3890

2 жыл бұрын

100% you should know the pKas of the major functional groups of amino acids.. I would honestly say that topic (plus enzyme kinetics and knowing 1 letter abbreviations of each amino acid) are perhaps the 3 topics you can almost guarantee will be on your MCAT

What would the charge be if the pH was = to the pKa? like if pH was 2 would it be +3 or +2?

@sciencesimplified3890

3 жыл бұрын

the Henderson hasselbach equation should show you it'll be a 50/50 mix... essentially the ration of (A/HA) = 1.... so half protonated half not protonated

@Mssejalmehta

3 жыл бұрын

@@sciencesimplified3890 Sorry I meant like in the example from the video- I understand how to quickly determine charges if they fall in between pH 2 and 6 but lets say the question asked to determine the charge of the overall polypeptide if it was at pH=2 or pH=6? like if the pH = the pkA of one of the actual R groups would the overall charge of the polypeptide be the value to the right or the left of the scale? So would the overall charge of the polypeptide for pH=2 be +2 or +3? Or in pH=6 would it be +2 or +1? Is there a quick way to determine the overall charge of the polypeptide at the pH values that equal the pKa in the way you set it up in the video or only exclusive for pH values that fall in between the pKa values of the R groups? Sorry if this sounds confusing...

Not clear how you came up with net charge of +3? You take average of 3 positive charges on right?

@ratyrat5

2 жыл бұрын

when you protonate all the functional groups (not just R groups, but also carboxyl and amines), three are net positive.

@cesaralex5782

2 жыл бұрын

I think that by protonating the O and S (to the left of the peptide, pKa 2 & 8) they remain in their neutral form, each one cannot make more than two bonds, so only consider the three groups on the right (4.01 min) for net charge. If anyone has more opinions.

Not clear how you came up with net charge of +3? Can someone explain, please?

@Michael-rr7um

4 ай бұрын

Sorry this reply is so late. In the drawing the 5 side groups he's referencing can have charges associated with them. The three functional groups that each carry a +1 charge are the groups labled with the pKa of 6, 9, and 11. At a pH of below 2, all of the functional groups will be protonated. However, only those 3 (pKa of 6, 9, and 11) will have a charge associated with them.