Isoelectric point and zwitterions | Chemical processes | MCAT | Khan Academy
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- Опубликовано: 4 окт 2024
- The isoelectric point of an amino acid is the pH at which the amino acid has a neutral charge. You will learn how to calculate the isoelectric point, and the effects of pH on the amino acid's overall charge. We will also discuss zwitterions, or the forms of amino acids that dominate at the isoelectric point. By Tracy Kovach. Created by Tracy Kim Kovach.
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This channel has really helped me through my Biochemistry module. Thanks.
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Simp
but...HOW do you calculate the PI with the R group? that makes it a lot more difficult then averaging two numbers together...?
You have to look at the pKa-value of all the functional groups. Say you have one amino-group and two acid-groups. You know that ionized, the amino-group will have a charge of +1 and each of the acid-groups will have -1. The goal is always to get a net charge of 0, which means the net charge of the two acid-groups has to neutralize the charge of the amino group. To do this, you add the pKa-values of the two acid-groups, and divide the sum by two. This way, each of the acid-groups will have a net charge of -0.5, since it will be 50/50 COOH/COO-. This way, you will have a net charge of 0, and you will have found the isoelectric point.
your explanation saved my life!
finally, I now understand, thank you!
so what do you do to "take into account" the R group if there is one?
Jane D divide it by3 i think
@@stevenkaleev8681 yes add to the pKa of amino and carboxyl groups and divide by 3 now to find average.
Steven Kaleev bro he’s probably graduated by now
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@@stevenkaleev8681 nope u have to make a number lines of pka of all group
Find the two pkas between which the zwitter ion exists - with zero charge
And apply the formula on that. U will get the iso electric point. Iso = same
It probably means same charge.
Very helpful and well explain- thank you!
Amazing explanation, thank you!
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Thank you soo much mam for neat and clear explanation 😇
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But wouldn't you change the pH of the Solution through the adding of the Aminoacid? Or do you just assume that the added Amount of Aminoacid is neglectible compared to the solvent?
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fantastic!
Now I'm ready for tomorrow's quiz thx!
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Never actually explained how to calculate the pI for a real amino acid...
There's another one. I think it's safe to assume it's a series, rather than a single video.
Thank you . very helpful
Thank you so much!
How do we calculate the pI when there are more than 3 ions...like suppose 2 NH3+ and 1 COO- group with different pH values??
we neglect the coo- as nh3+ is in majority so, we take the average of the pk values of nh3+ i.e the pi would approximately be 9.
you could also consider the 2 pk values that are close to each other like here both the nh3 would have similar values so we take their average
very helpfull
Thanks Mam
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I have a doubt about then Pk .... please clear the concept through a video
this is very helpful! thanx
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I want to ask this teacher that were you at UF teaching Centre ???There are videos of Biochemistry on youtube on uf teaching centre channel and her voice is exactly like yours...Your voice is driving me crazy...
useful vid thanks
Thanks 🔥👍🏻
Well explained!
at 4:20, on average from the amino acids groups, the pKa of carboxylic acids is 2. So that means there is not standard set value of pKa for a single carboxylic acid? Then what would be the pKa of only the carboxylic acid and nothing else attached to it?
Your voice sounds like Brook from OITNB!!
Brilliant, thanks!
good explanation as always........And you have a very neat handwriting :-) :-D
Why isoelectronic point of amino acid which have acidic or basic side chain is average of two similar group ?
Thanks❤️
So do we use the .5(pKa1 + pKa2) only when the amino acid is in a solution of water?
So if we take the side chain into account is it (pka1+pka2+pk3)/3 then?
No. If it's a negatively charged amino acid, PI= pka+pk1/2. If it's a positively charged amino acid, PI= pk2+pka/2. If you think about the meaning of PI, this makes more sense.
Great thanks you!
thank you
Hi..How can i calculate the pI of the arginine with a side chain of guanidino group??I dont understant any of it..could you please explain??and how the involved chemicals group determine the pI of arginine (in your explanation name the charges that are present on the ionisable groups??
Question, why would the pH of the -1 charge amino acid be that of 12, but the pKa is that of 2 for the fictional example?
Superb👍👍👍
How do know which two of the 3 pKas to use when the side chain has a pka value as well?
Thank you! :)
lovely sound
No wonder why you got hired for Khan.. you're so good :) I guess he hires people who are better than him ;) and yes, he can teach well too.
Can you please tell me why pI can't be 7???
Why would Oxygen want to give up a Hydrogen to a Nitrogen?
If oxygen is more electro-negative, then why would it give it up?
The oxygen isn't giving its hydrogen to nitrogen. Protons are being given to or taken from the amino acid molecule depending on the pH of the solution that this amino acid is in. In a low pH solution (pH
Very helpful thanks!
But also, your voice stuck out to me, and it reminds me of most transwomen's voices who have mastered voice control. If that's true, then holy, I am jealous
Hi I have a question ;-; can someone help
this showed up in the practice module:
electrophoretic separation of leucine from a protein sample would be the least effective at which of the following pH value? 7.4, 2.4, 1.4, and 0.4.
I know for leucine since it is alkyl its isoelectric point is around ~5.5. but how does the fact that it is a zwitterion at ~5.5 have to do with the least effective pH for electrophoretic separation of levine being at 7.4?
Thank u in advance!!!!
I think its because an amino acid does not move unless it gains a positive or negative charge. So for the zwitterion to move, it needs to gain a charge. Placing the protein sample in a pH solution that is close to the pH of the zwitterion will not cause it to gain any charge. For it to be separated effectively from the sample, it needs to placed in a pH environment that is a lot higher or lot lower. 7.4 is too close in value to the pH of Leucine for it to gain charge and move. If it was placed in a pH solution of 0.4, it will move a lot farther and get separated from the rest of the protein sample a lot better. I hope this helped.
How is COO- a proton donor when it has no Hydrogens
what if the ph is 6 neutral?
Pronounced zvitter not switter
really? im confused. i thought each residue contains a carbonyl group (C=O), which is a good hydrogen-bond acceptor, and, with the exception of proline, an NH group, which is a good hydrogen-bond donor.
Zoohra A they're not talking about hydrogen-bonding.
YEAAAAAAAAAAAAAH
explain what is pKa before writing it ....its still confusing ...though the overall idea was good ...thank you .....
Pka is a pressure constant used in equilibrium conditions
If you're in biochem that means you made it through Ochem and Gen chem. You should already be familiar with pka
Biswajit Saha the pka is the log of a solutions H+ concentration. It is a measure of acidity.
the pka's are backwards
It sounded like Mandy from Totally Spies
savior T^T
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Voice 😀
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I can recognize the voice.
in the video you put the pka=9 on the +1 side, COOH dissociates at pka=2ish
Informative video, not a fan of the nasally voice
I hate MGD
your pronunciation of zwitterion is a tad lol.
+MrRabastan How is it supposed to be pronounced..?
the 'w' is pronounced like a 'v'
so like: Zvitter ion
MrRabastan
Ah I never knew that, cool!
thank you!
Thank you.
thanks
Great explanation, thanks!