The concept of pKa and pH "fighting" for the proton clarifies this concept for me SO much. Now I don't need to memorize this, I UNDERSTAND it! Thank you Leah!

@Leah4sciMCAT

5 жыл бұрын

Glad I could help!

My goodness, you have such a gift for teaching complicated material in such a way that us "less" genius folk can really grasp it! Thank you so much for sharing your gift!

@Leah4sciMCAT

6 жыл бұрын

You're very welcome, and just keep working on it. It took me a while to understand some of these concepts.

You are simply amazing. I never really thought that I would grasp the concepts after reading my textbooks, but your videos have proved me wrong. Your explanation in simple terms is just great.

@Leah4sciMCAT

3 жыл бұрын

Awesome! So glad you understand it now!

Your MCAT shortcuts are saving my life! Testing in 3 days and this is making things so much clearer than they have been during my whole study process.

@Leah4sciMCAT

7 жыл бұрын

I'll keep my fingers crossed for you! Glad I could help

@arsildarouiche892

5 жыл бұрын

How'd you do on the MCAT?

Thank you so much Leah, I'm an undergrad pre-vet student and in my biochemistry class I was so lost when the professor was doing these problems. I have a test Monday and now I understand this so well, thank you!!!

@Leah4sciMCAT

4 жыл бұрын

You're welcome! I'm glad I could help :)

best explanation and answering scheme ever! i wish i have known you earlier and now im rushing for my 2nd MCAT.. all the best for everyone who is running with me!

@Leah4sciMCAT

2 жыл бұрын

So happy to help! Regarding the MCAT, why are you rushing? I encourage you to let your full length practice scores guide you instead of the calendar so that you only test once you KNOW you are ready. Check out this for more: leah4sci.com/mcatready

your teaching is awesome. clear. even for Korean. thanks a lot. this helped me so much.

@Leah4sciMCAT

7 ай бұрын

Glad you liked it!

You just saved my biochemistry teste!!!! Thank you so much I was having troubles with this

@Leah4sciMCAT

5 жыл бұрын

You are very much welcome :)

Thankyou a lot......You came as a blessing......Was struggling with this topic for years .......U deserve more subscribes taking into account the content on ur channel.......A lot of useless channels have more subscribers than urs where they just blurt out the formulas without such beautiful explanations......Do not know why people arent accepting such amazing content......U have really good teaching skills......Please feel proud of yourself .......Just Amazing

@Leah4sciMCAT

3 жыл бұрын

Awww, thanks, I really appreciate your kind words. I'm glad to know my videos are helping you to understand!

I loveee your videos!! This is making studying for the mcat soo much easier! Thank you Leah! :D

@Leah4sciMCAT

5 жыл бұрын

awwww! Thank you and you're welcome :)

Definitely understand this way more now then when I learned it before. Amazing, thank you!

@Leah4sciMCAT

2 жыл бұрын

You are so welcome, happy to hear that it's helping you!

Excellent simplification of a complicated topic. You are really gifted. Thank you for your beautiful explanation.

@Leah4sciMCAT

Жыл бұрын

You're welcome, so glad it was helpful!

Bless your soul!! I am a second year biochem student and this video was super helpful!!! Thank you

@Leah4sciMCAT

5 жыл бұрын

Glad you enjoyed it!

@TheRealK.

4 жыл бұрын

Jma3t l biochimie 😂😂

You made it so simple! Made my concepts clear . Thank you

@Leah4sciMCAT

6 жыл бұрын

Glad I could help!

Seriously, you just explained it a whole lot better than my biochem teacher! Thanks, hope it helps on the test.

@Leah4sciMCAT

5 жыл бұрын

Glad to have helped you understand the topic better. You're welcome :)

Hi Leah! Thank you so much for this video! Quick Question! Why do we know to deprotonate the hydrogen off of the carboxyl functional group rather than off the tyrosine (6:30 in the video). Thanks!!

@Leah4sciMCAT

2 жыл бұрын

The entire molecule is known as the amino acid tyrosine (not just the side chain). At this point in the video, we are determining the net charge of tyrosine between a pH of 2.2 and 9.1. Since the pKa of the carboxyl group is 2.2, if we are above that value in pH, the carboxyl group will be deprotonated. Any pH above 2.2 will yield a deprotonated carboxyl group. If still struggling on this topic, read my tutorial at leah4sci.com/amino-acid-charge-in-zwitterions-and-isoelectric-point-mcat-tutorial/

Very clear and well broken down. Super easy to understand. Thanks!

@Leah4sciMCAT

6 жыл бұрын

You're very welcome :)

I've been struggling in class!!! I haven't taken chemistry in 5 years. I am now in biochemistry and all I can say is thank you!!!! You're my new professor. You are precise, in depth, and relate all the information. Once again thank you and keep it up!! Sorry do you mind posting the link to the following video please? I can't find it.

@Leah4sciMCAT

8 жыл бұрын

thank you. The next video will be uploaded shortly

Thank you so much for these videos, Leah!! Your channel is a real blessing!! One question- why is the pKa on the amine group in tyrosine 9.1 instead of 9.6? I thought it was always the same on every amino acid being 9.6, so I've been using that for my calculations in these types of questions. But here you have it as 9.1, so is it different for every amino acid? If so, how do we know what it will be? Thanks so much again:))

@Leah4sciMCAT

3 жыл бұрын

Awww, thanks for your kind words! Technically, the pKa of the amino group is slightly different for every amino acid. It’s fine to use 9.6 as an estimate for any one of them, when calculating pI. There’s no easy way to predict how the pKa of the amino will differ, based on the particular amino acid you’re looking at. You can find a chart of various values on my Amino Acids Practice quiz found here: leah4sci.com/amino-acids-practice

This very educational...you are really good in explaining. I am very happy for this, since this is a much more important subject than most Dairy technologists understand. I have used this many times to obtain better process results in my machine designs.

@Leah4sciMCAT

2 жыл бұрын

Happy to help!

Another high-recommendation comment. Clarity in simplicity; well-curated examples in efficient instruction.

@Leah4sciMCAT

3 жыл бұрын

Wow, thanks so much for your kind words!

My lifelong dream has been to be a doctor and I know I could do it. But your videos are really making me consider being a professor. You don't know how much of a relief it is to watch your videos and finally understand something that was confusing during a lecture. That ah hah moment when something makes complete sense is something that I would also like to do for other people. You are not only smart but you convey the material in a way that clicks with me. You are gifted, please don't stop making these videos.

@Leah4sciMCAT

4 жыл бұрын

Thank you so much! Whatever you choose to do, if it's your passion, go after it and don't give up!

best isoelectric point vid I've watched (out of 4 others). Question though, why don't you include serine and threonine with their hydroxyl groups as part of the "if protonated it's neutral" group at 11:45 in the video? Thanks

@Leah4sciMCAT

5 жыл бұрын

good question. I chose to focus only on the amino acids that have pKa values significant enough to consider for the MCAT. Serine for example has an OH but is not highly ionizable due to lacking stability for the resulting negative charge. As such we just assume it's always protonated and neutral in regards to MCAT/biochemistry

Hi Leah, you are awsome, thank you so much for this, just a small question, @ 12.39 you said for the upper 2 pKa values, and referring to the carboxyl group and the Side chain, is not the upper values 9,1 and 10,1 so it should be the amine group and the side chain?

@Leah4sciMCAT

4 жыл бұрын

We're looking at the 2 higher numbers. With basic amino acids that will be the alpha amino group and the side chain

your videos are always awesome. thank you

@Leah4sciMCAT

5 ай бұрын

Glad you like them!

Leah will the MCAT provide the pKa's? Or do we have to memorize them?

@Leah4sciMCAT

8 жыл бұрын

+Funksolid I recommend memorizing general values. Carboxy ~2, Amine ~10, Side chain carboxy ~4, HIS 6, basic ~11+

You just simplified this to its simplest form. Thank you

@Leah4sciMCAT

5 жыл бұрын

You're very welcome!

Hey Leah I am a bit confused on why Lysine @18:15 would have a charge of zero at the PI of 10. You mentioned at @12:22 that we look at zero for lower which referred to Asp, Glu, Cys, and Tyr, and we look at upper +1 which referred to His, Arg, and Lys. Please explain this to me because I am very confused. Thanks

@Leah4sciMCAT

6 жыл бұрын

The trick refers to identifying the charge when there are 3 pKa values. This is simply what you average to find the pI. However, the charge should be zero at the pI value given its definition. Or did I misunderstand your question?

Thank you, I finally understand it!

@Leah4sciMCAT

7 жыл бұрын

You're very welcome! glad to help

damm.... it's such a awesome video. Learned more than 10 hour biochem class !!!!!! thank you soooooo much!!!!!!!!!

@Leah4sciMCAT

5 жыл бұрын

You are very much welcome! Glad the video helped :)

This was extremely helpful! Thank you very much!

@Leah4sciMCAT

8 жыл бұрын

you're very welcome

You are awesome!!!!! Thank you so much!! Do you only make videos for biochemistry?????

@Leah4sciMCAT

7 жыл бұрын

Mostly Organic Chemistry leah4sci.com/KZread and MCAT on this channel

Hi, this might sound like a very stupid question, but I'm just trying to self learn this whole subject; we havn't reached it in school yet: Where do you get the pKa values from? Thanks in advance!!

@Leah4sciMCAT

6 жыл бұрын

This series will help: leah4sci.com/mcat/mcat-chemistry/acid-base-ph-and-pka-calculations-in-mcat-chemistry/

Extremely helpful. THANK YOU!

@Leah4sciMCAT

5 жыл бұрын

You're welcome! Glad the video helped.

I am grateful to you for this explanation😩❤️

@Leah4sciMCAT

4 жыл бұрын

You are so welcome!

All of your videos are wonderful. Thank you

@Leah4sciMCAT

2 жыл бұрын

You're welcome. So glad you like them!

Thank you so much. You made it super simple

@Leah4sciMCAT

7 жыл бұрын

You're welcome :)

When you are looking at the alcohol on the tyrosine side chain @ 11:17, why is it that the proton is being added to a deprotonated alcohol? Why not an already protonated alcohol?

@Leah4sciMCAT

7 жыл бұрын

the pKa refers to the ability to add/remove a proton to a specific form of the molecule. Tyrosine with an OH is very unlikely to accept a proton given that it is a very poor base. however, Tyrosine with an O- is likely to accept the proton. This works the same in reverse for donating the proton. O- has none to give, OH is likely to give it up.

Thank very much. Very easy and simple to understand

@Leah4sciMCAT

6 жыл бұрын

You are very welcome!

thank you for this video. it seriously helped me out.

@Leah4sciMCAT

5 жыл бұрын

You're welcome! :)

@16:50 Why are you adding a Hydrogen to the NH group if you're deprotonating it? The pH is greater than the pKa so it wins one for the solution and deprotonates the group so shouldn't the NH group become a N with a charge of -2?

@Leah4sciMCAT

4 жыл бұрын

Careful, every H has it’s own pKa value. When given pKa values for AAs you’re looking at the +H. To remove a neutral H (to get N-) you’d need another pKa value, for N-2 you’d need yet another. Both are well beyond the scope of our pH scale here

Also, @ 15:14 you drew Lysine lacking H on the hydroxyl side and amine side? am I missing something here!

@Leah4sciMCAT

8 жыл бұрын

15:14 covers Asp

wao thankyou so much...it really helped me to understand PI concept.👍

@Leah4sciMCAT

7 ай бұрын

You are so very welcome!

At baseline, is the Amino group supposed to be NH3? At 16:40 I got a little confused about going from NH to NH2 with the lone pair after the solution won the H+. I just wanted to make sure I didn't miss a step! Thank you!

@Leah4sciMCAT

2 жыл бұрын

Thanks for asking! I wouldn’t refer to anything as a ‘baseline’. In this case, the amino group can only be considered protonated (NH3+) or deprotonated (NH2). At 16:40, don’t take any meaning from the fact that I have the amino written as NH. I simply was waiting to write in the number of hydrogen atoms, after my assessment of whether the group would be protonated or deprotonated.

can i clarify the something? where did you get the pka value, or how can we solve this pka value? thank u

@Leah4sciMCAT

3 жыл бұрын

Thanks for your question! The pKa values are constant for and specific to any given amino acid side chain. Some professors might have you memorize these values, but you can always find them in a table or appendix in the back of your textbook. It is important to remember the pKa of the free carboxylic acid group as 2.2 and the pKa of the free amino group as 9.1.

Leah! what does it mean to know the amino acid structures at ph 7.4? does this mean they are in zwitter ion form?

@Leah4sciMCAT

3 жыл бұрын

Thanks for your question! The physiological pH of the human body is known to be ~7.4. It’s important to know the structures at this pH, simply because of its relevance to human body chemistry. Zwitter ions contain an equal number of positively and negatively charged groups, meaning they are overall electrically neutral. Because of the pKa values of their side chains, not all amino acids are neutral zwitter ions at physiologic pH.

Easier way of thinking about it is if the amino acid is acidic, use the lower two. If it’s basic use the upper two.

@Leah4sciMCAT

Жыл бұрын

Use whichever method helps you best!

Leah @ 5:10 you assume that tyrosine initially lacking hydrogen at the carboxyl why?

@Leah4sciMCAT

8 жыл бұрын

I started with a random structure and adjusted for the appropriate pH

is there anyway to calculate pKa values for R groups, or do we have to just memorize them all

@Leah4sciMCAT

5 жыл бұрын

You have to memorize, however not the exact values. See the estimates I recommend in the video

Crazy easy! She is an awesome tutor !

@Leah4sciMCAT

5 жыл бұрын

Thank you for your kind words!

Your videos are amazing. Thank you!❤

@Leah4sciMCAT

Жыл бұрын

You are so welcome!

Thank you so much Awesome video

@Leah4sciMCAT

4 жыл бұрын

You're very welcome!

it's really helpful to understand this!!

@Leah4sciMCAT

7 жыл бұрын

Glad it helped

@6:32 , how did you get the OH to have a net charge of 0? I figured that the charge would be +1 since the pH of 5 is less than 10.1 so there would be a protonation and thus would gain a +1 charge.

@Leah4sciMCAT

2 ай бұрын

When looking at ionizable groups, take into account what happens when they get protonated/deprotonated. You are correct that the OH will be protonated, but what happens when it IS protonated? You get OH (not OH2+) When deprotonated you get O-

Lysine has an additional COO- that you didn't draw in your example? WHat affect does this have on

@Leah4sciMCAT

4 жыл бұрын

I don't think you finished your question. affect on what?

Great video. Thanks for the help!

@Leah4sciMCAT

4 жыл бұрын

You're very welcome!

For tyrosine why are the two lower pKa's being used? In my homework for biochem it says to use the higher two pKa's. I am very confused now, could you please explain.

@Leah4sciMCAT

2 жыл бұрын

The isoelectric point is the pH of the solution at which the net charge of the molecule is zero. Therefore, in order to calculate pI, we average the two pKa values that are just before and just after the pH range that gives us a net charge of zero. In this case, for tyrosine, that would be 2.2 and 9.1

Wow, clear explanation 👏

@Leah4sciMCAT

2 жыл бұрын

Glad it was helpful!

Such a genius. Thanks!

@Leah4sciMCAT

4 жыл бұрын

Awww thanks, you're so welcome!

this was really useful, thanks!

@Leah4sciMCAT

4 жыл бұрын

You're welcome!

can you please put a video or message me on how you would find the pI of a polypetide that has 2 (R), 7 (k) ,1 (N) ,2 (H), 8 (E), 9 (D), 1 (C) ....i find your trick very very helpful when it comes to peptides that are like short chains of amino acids but how would i apply this to a polypeptide this long...

@Leah4sciMCAT

6 жыл бұрын

I'm sorry, but I don't offer tutoring through KZread comments. Try re-watching the video to really get the trick down. For more help with questions like this and more, I recommend joining the MCAT Study Hall. For more details visit join.mcatstudyhall.com/ or contact me through my website leah4sci.com/contact/

So for MCAT purposes: is it a good idea to memorize all the pKa's for amino acids or do they tend to be given in the passage/figures?

@AmyStylinson

6 жыл бұрын

Diana Ramirez no, they are not given. Memorize the pka values for all basic and acidic amino acids. A good mnemonic: ST RKY CHED. Learn all the pka values of the amino acids of the mnemonic!

@Leah4sciMCAT

7 ай бұрын

Yes and no. YES you want to memorize the pKa values, but not the exact number. Instead memorize an approximate value for each as I teach here leah4sci.com/amino-acid-charge-in-zwitterions-and-isoelectric-point-mcat-tutorial/

Shortcut: if it is an acidic aa, pI is the average of the pka of two carboxylic ends (acidic has negative charge) and if an aa is basic, the pI is the average of the two amine groups. For the rest of the aa, it is just a regular average between two numbers.

@Leah4sciMCAT

8 жыл бұрын

Don't forget the tricky ones though?

Really basic question but how do you know whether to add a plus or hydrogen when things become pronated?

@Leah4sciMCAT

5 жыл бұрын

I'm sorry but I don't offer tutoring through KZread comments. For help with questions like this and more, I highly recommend joining the MCAT Study Hall. For more details visit join.mcatstudyhall.com/ or contact me through my website leah4sci.com/contact/

Do we use the structure of amino acid at pH = 7 to determine the IP?

@Leah4sciMCAT

2 жыл бұрын

No, not in all cases. The isoelectric point is defined as the pH at which the net charge of the molecule is zero. Not every amino acid has a net charge of zero at a pH of 7. The examples of aspartate and lysine in this video prove that.

This video makes calculation of pi value really very easy.

@Leah4sciMCAT

4 жыл бұрын

So glad to hear my video helped you understand!

If the pH of a sol'n is the the same as a pka of a group, is that group protonated or deprotonated?

@Leah4sciMCAT

5 жыл бұрын

I'm sorry, but I don't offer tutoring through KZread comments. For help with this and more, I recommend joining the MCAT study hall: join.mcatstudyhall.com/

great video helped me a lot

@Leah4sciMCAT

4 жыл бұрын

Glad it helped!

Great! Thank you so much.

@Leah4sciMCAT

3 жыл бұрын

You are welcome!

Awesome! Thank you!

@Leah4sciMCAT

6 жыл бұрын

You are very welcome!

Super helpful!

@Leah4sciMCAT

3 жыл бұрын

Thanks!

Thank you so much.

@Leah4sciMCAT

3 жыл бұрын

You're welcome!

Loved the way u taught

@Leah4sciMCAT

3 жыл бұрын

Thanks so much!

For the tyrosine example, why is it -1 when the PH is 9.6? The ph is less than the pka for the R group, meaning we have to protonate it, giving it a charge of +1. The sum of +1 and negative one (from the carbonyl group) will be zero, not -1.

@Leah4sciMCAT

3 жыл бұрын

Thanks for your question! When the R group of tyrosine is protonated, it has a charge of zero. It exists as an -OH group off of the benzene ring. You will not see it exist at -OH2+. Therefore, at a pH of 9.6, the sum of 0 and -1 (from the carboxylate) gives a net charge of -1 for tyrosine.

@joannaelhaj3571

3 жыл бұрын

Leah4sciMCAT thank you for your reply. I wasn’t aware of this rule. So if a NH3+ needs to be protonated, you keep it as a +1 charge. If you have to deprotonate NH3+, it become 0. If an OH group needs to be protonated, it will have a charge of 0 and if you have to deprotonate and OH group, it will have a charge of -1, correct? Also usually when finding pI, you start with the most protonated form of the amino acid, would that be used to see if the overall charge of the amino acid is a 0 or +1, or are you specifically looking at the charge of the side chain? Thank you

Excellent !

@Leah4sciMCAT

Жыл бұрын

Glad you like it!

you are awesome!!! Go on plz never stop.

@Leah4sciMCAT

4 жыл бұрын

Awww, thanks!

thx for this video really helpfull for iit jee

@Leah4sciMCAT

6 жыл бұрын

You're very welcome

Thank you so much

@Leah4sciMCAT

4 жыл бұрын

You're very welcome!

THANK YOU SO MUCH

@Leah4sciMCAT

7 жыл бұрын

You're very welcome

Thank you so much ❤❤ ..ur the best :)

@Leah4sciMCAT

4 жыл бұрын

You're very welcome!

I purchased Magoosh MCAT to study and your videos have helped tenfold what their material has... The psych/soc material is excellent through Magoosh, but other than that, I wouldn't recommend.

@Leah4sciMCAT

3 жыл бұрын

I'm sorry to hear that hasn't worked out for you, but happy to hear my videos have helped you. Check out my website for even more resources: leah4sci.com

LIFESAVER!

@Leah4sciMCAT

9 ай бұрын

Glad to help!!!

why are you giving the amine a hydrogen @16:55 when it's being deprotonated?

@TheIndianShopper

5 жыл бұрын

From NH3 to NH2...that is the deprotonation, she just wrote 2 later

@Leah4sciMCAT

7 ай бұрын

Deprotonation refers to loss of the third acidic hydrogen, but there are still 2 hydrogens remaining (3 -> 2)

THANK YOU!

@Leah4sciMCAT

5 жыл бұрын

You're welcome! :)

Thank u so much

@Leah4sciMCAT

3 жыл бұрын

You're welcome 😊

isn't the R group for Aspartic acid negatively charged? I mean at physiological pH. explain please

@Leah4sciMCAT

7 жыл бұрын

It is! Watch the charge video in this series

@jhonnydavidyovera2021

7 жыл бұрын

+Leah4sciMCAT yeah you said it is negative but in this video you said it is neutral. anyways I got the idea tho. you r great

@Leah4sciMCAT

7 жыл бұрын

What point in the video? it sounds like you understand the concept which is the goal but if you point me to the error I can take a look

I got an A in my orgo thanks to your orgo videos. I am sure that I will get an A in my biochem through your videos as well!

@gabenir5117

5 жыл бұрын

Yes, same here! Got a 99% and 97% both in Orgo 1 and Orgo 2 respectively only because of Leah. Hope to get an A as well in biochem. Good luck!

@Leah4sciMCAT

5 жыл бұрын

@kimbel Bradley great job! glad the videos helped. :). Best of luck on your Biochem exams! :).

@Leah4sciMCAT

5 жыл бұрын

@Gabe Nir awesome! Best of luck on your Biochem too. Hope you shared the channel to your friends ;)

@zoeydavis6064

4 жыл бұрын

@@gabenir5117 I am amazed by both of you.

how did you know to use 2.2 and 9.1?

@Leah4sciMCAT

5 жыл бұрын

At which specific point in the video?

Thank you.

@Leah4sciMCAT

4 жыл бұрын

You're welcome

Thank youu ❤️❤️❤️❤️❤️😭😭😭

@Leah4sciMCAT

2 жыл бұрын

You're so welcome!

Thanks ma'am

@Leah4sciMCAT

5 жыл бұрын

You're welcome! :)

OH MY GOD, my teacher didnt explain this, the book didnt explain this. THANK YOU SO MUCH.

@Leah4sciMCAT

3 жыл бұрын

You are so welcome!

thanks a lot

@Leah4sciMCAT

7 ай бұрын

you're welcome!

oh my goodness I can't believe I could understand this much easier...

@Leah4sciMCAT

Жыл бұрын

Happy to help!

She makes me so happy

@Leah4sciMCAT

5 жыл бұрын

I'm glad I can make you happy :)

isnt aspartic acid positively chaged?

@Leah4sciMCAT

3 жыл бұрын

Great question! The net charge of aspartic acid (or of any amino acid with ionizable groups) changes with the pH of the solution. This is because each of the ionizable groups on the molecule has a different pKa value and can exist in either its protonated or deprotonated form depending on the pH.

isn't Cysteine and Tyrosine neutral AAs?

@Leah4sciMCAT

Жыл бұрын

Their side chains are neutral in charge, if that's what you're asking. For help with questions like this and more, I recommend joining the MCAT Study Hall. For more details, visit join.mcatstudyhall.com/ or contact me through my website leah4sci.com/contact/ You can also view my free Amino Acids series, practice quiz and cheat sheet at Leah4sci.com/AminoAcids

AWESOME!!!!!!!!!!!! Hallelujah!

@Leah4sciMCAT

7 жыл бұрын

Very glad you enjoyed it!

Marvelous

@Leah4sciMCAT

3 жыл бұрын

Thanks!

great video

@Leah4sciMCAT

7 ай бұрын

Thanks! Glad you liked it!