oh my god, I couldn't understand this for weeks,I couldn't find any good explanatory videos and you just answered all my questions. I have my biochemistry exam on Monday. thank you
I can't express how greatfull I am. I've been trying to understand those concepts for weeks with my regular teacher and failed miserably. This explanation was so clear, i finally understood!! Thank you so much!!
Thank you so much Lea! I was struggling with this and got a 503 MCAT, now I ended up getting at 517 and will make a video about how I did it! Thank you so much!
Just brilliant. Will be sharing with my past BioChem professor (she loves solid educational videos - knows students all have different learning styles) along with my Pre-Med base. Regret not thoroughly watching through these years ago.
Glad I could help keep the meltdown away! Might I suggest booking some time just for yourself for a walk, bath, reading or something else enjoyable where you can completely unplug? Even 20 minutes can make a huge difference.
@ time 13:15, you wrote glycine as having only one H on the Nitrogen, when it actually has 2 H's. This really confused when you started to count charges...
I’m sorry for the confusion and for the late reply. When neutral and in its de-protonated form, the free amino group of glycine should appear as -NH2. At no point does it actually exist with a single proton. I simply had it appearing that way at the beginning of the problem before I determined if the group was in its protonated (-NH3+) or deprotonated (-NH2) form.
Thanks to this wonderful video! But I still don't understand that why -COOH is still -COOH after protonation and also why CH3NH3+ is still CH3NH3+ after protonation?
Because -COOH is already a protonated form of carboxyl. It can only be deprotonated now to -COO- (Negatively charged). The -COO can not accept two protons. Just as the -NH3+ can not accept a 4th proton. This is determined by the atoms' valence and number of electrons
Can someone answer this for me? I thought a molecule that has more H+ ions is BASIC and molecules that don't have that many H+ is acidic? Right or wrong?? for example which is the base and which is the acid of these 2......NaH2PH4 and NaHPO4 and why?
Yes, the amine will be de-protonated at pH 13. It goes from NH3+ to a neutral NH2. The amine group will never be written as NH (and if it was, it would be negative in charge).
just wanted to clarify, at ph=13, the ph is greater than pka 9.6 of amino group, so amino group should be deprotonated to NH2 from NH3+ right? and thats why you get the charge on the amino group as 0?
I'm sorry but I don't offer tutoring through UA-cam 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/
So you said that the neutral form cannot exist, but that the zwitterion is the neutral form and then you claimed that it is the most common form, please elaborate I'm confused
I apologize for the confusion. The amine and carboxyl groups cannot both appear in their neutral form at the same time. In nature, we most commonly find amino acids as a zwitterion where the amine holds a positive charge and the carboxyl hold a negative charge. Overall, these two charges cancel out, creating a net neutral charge for the molecule. The idea is that neither group is neutral by itself, but together they form a net neutral molecule.
I think you’ve got the distinction! The pH looks at the concentration of hydrogen ions in solution, while the pKa is a constant for any given molecule. The pKa gives us information about the acidity of a certain proton on the molecule and whether that proton will dissociate or not at the specified pH.
I'm sorry, but I don't offer tutoring through UA-cam comments. 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/
She drew H(space)N so that she eventually fills in all the numbers as she showed the specific pH values. Depending on the pH, the amino group is protonated or deprotonated, and she shows that with her drawings.
For the class or MCAT? My biochem resources are specifically designed for the MCAT. For more help with MCAT biochem, I recommend joining the MCAT study hall. Full details: join.mcatstudyhall.com/
at ph 13 why did the amine group get protanated ... is should be deprotonated ryt ? bcoz the surrounding has got less H+ ion they y did the NH was protonated ....im confused ..
+Leah4sciMCAT just nw watched ur vid again ..nw its clear just pls clarify the doubt above ...ie protein we eat has their ammino acids in zwitter form ? is it ?
Thanks for asking! A pH of 1 is less than the pKa of the free carboxylic acid group (~2.3) on an amino acid. Because of this, the group will appear in its protonated form as -COOH and is neutral in charge.
i was confident until you did the example with glycine and misdrew it... it got me so confused during the entire example and now I'm just really anxious and confused :( ... please fix this....
Excellent job Leah, thanks a lot! Just one question, regarding the quiz on your website: In part 3, we are asked to find the charge of Cys at PH = 4. Pka values for Cys are as follows: (Pka(COOH):1,71, Pka (NH2): 10,78, Pka(R): 8,33 ). The solution suggests change 0 for the side chain. Could you please explain this to me? I would expect to see +1 for the side chain and not zero, as PH is much less than the Pka for side chain, which means that the side chain should get protonated (conveting to S2H+ from SH). Am I missing something? All help would be appreciated.
You're very welcome! Since I don't offer tutoring over social media, I would first suggest you use the download link at the bottom of the practice quiz to access the PDF quiz solutions. If you would like a more detailed explanation, I recommend joining the MCAT Study Hall. For more details visit join.mcatstudyhall.com/ or contact me through my website leah4sci.com/contact/
I’m sorry for the confusion and for the late reply. At no point does glycine actually exist with a single proton on the nitrogen or with an uncharged, de-protonated oxygen on the carboxy group. I simply had it appearing that way before I determined if either group was in its protonated or deprotonated form. There really is no “starting molecule” of glycine. It will exist at different charge states, depending on the pH of the surrounding solution. We always have to consider the pH before determining how glycine will appear.
I'm confused. Ka is a constant for any given acid, right? So how can it be proportional to the hydrogen concentration? Constants aren't proportional to things! Ahh!
Sorry you're so confused; let's get things cleared up for you. Yes, Ka is a constant for any given acid. Maybe it would be better to say that Ka is proportional to the ratio of [H+]/[HA]. It stands to reason that acids which produce a higher quantity of H+ per unit of acid would have greater Ka values (and thus be more acidic). So even though the Ka doesn’t change for a given acid, it is variable between different acids based on how much H+ that particular acid produces.
An amino acid is an organic compound that contains both amine and carboxylic acid functional groups. In this video, I first look at acetic acid and methylammonium, as examples of how those same functional groups would behave on their own at various pH values. Then, to apply that knowledge, I turn to the example of the amino acid glycine at 12:37 to explain how these functional groups would function together within the same molecule at various pH values.
oh my god, I couldn't understand this for weeks,I couldn't find any good explanatory videos and you just answered all my questions. I have my biochemistry exam on Monday. thank you
thank you! glad to help
Good luck on Monday!
You are truly gifted when it comes to explaining MCAT content. Thank you!
Thank you for your kind words!
I can't express how greatfull I am. I've been trying to understand those concepts for weeks with my regular teacher and failed miserably. This explanation was so clear, i finally understood!! Thank you so much!!
I'm sorry you've had such a struggle with it, but happy that I was able to help you understand!
Thank you so much Lea! I was struggling with this and got a 503 MCAT, now I ended up getting at 517 and will make a video about how I did it! Thank you so much!
That's fantastic, congratulations! And yes, make that video and help others see how they can reach their goals, too!
Just brilliant. Will be sharing with my past BioChem professor (she loves solid educational videos - knows students all have different learning styles) along with my Pre-Med base. Regret not thoroughly watching through these years ago.
Please do, and thanks for sharing!
You are just so amazing Leah! You have assisted with turning the cogs in my brains just that little bit more every time!
I'm so glad to hear that I've helped it all click into place!
It finally made sense to me while looking at Le Chatelier's principle! Thanks!!!
Glad the video helped! You're welcome :)
This concept help me to crack jee advanced 2020 question in seconds ❤❤ 👍 thanks 😊
YES to saving time on exam questions!
Don't understand everything yet but very clear explanation and presentation. Thank You.
You're very welcome! I'm glad it's helping to clear things up. Go back and rewatch a few more times to help solidify the concepts.
THANK YOU OMG THANK YOU!!! YOU SAVED ME! IM SO GRATEFUL FOR THIS CHANNEL!!!!
You're welcome! Happy to help!
I think you may have just saved me from a meltdown. Thanks ;)
Glad I could help keep the meltdown away! Might I suggest booking some time just for yourself for a walk, bath, reading or something else enjoyable where you can completely unplug? Even 20 minutes can make a huge difference.
Just found this channel of yours right now! Keep up the good work Leah!!
Thank you so much!!
I'm Really thankful to u for making this tutorial.. finally understood the concept 👍
Happy to help!
Excellent job! I totally understand it now. Thank you so much.
+Ram Palepu You're very welcome! Glad to help
You explain everything thoroughly! Very good videos. I've recommended this to other students
Thanks so much, I really appreciate that!
OMG THIS IS AWSOME , I was so confused, you broke it down so so so well!!!!
Thanks so much!
Your voice is like ASMR, It's relaxing and soothing. I like it a lot, ever think about doing deep sleep mix tapes? 🌝
hahaha, I haven't, but thanks!
thank you so much i struggled so much with this topic
It's a tough topic, happy to help!
Thanks a ton, this concept was troubling me from past 2 days 😇😇😇😇thank you thank you thank you for making it crystal clear.
Glad it helped! You're very welcome!
What an AWESOME explanation!!
you have just lightened my road 😃thank you very much .
You're very welcome, so glad it helped!!
You are a tremendous teacher.
thank you
Saved me once again ❤ thanks for doing what you do!
You're very welcome! Glad it helped :)
Clear and simple as always, thank you.
You're very welcome!
@ time 13:15, you wrote glycine as having only one H on the Nitrogen, when it actually has 2 H's. This really confused when you started to count charges...
Yeah lol
I’m sorry for the confusion and for the late reply. When neutral and in its de-protonated form, the free amino group of glycine should appear as -NH2. At no point does it actually exist with a single proton. I simply had it appearing that way at the beginning of the problem before I determined if the group was in its protonated (-NH3+) or deprotonated (-NH2) form.
Thanks to this wonderful video! But I still don't understand that why -COOH is still -COOH after protonation and also why CH3NH3+ is still CH3NH3+ after protonation?
At which specific point in the video?
Because -COOH is already a protonated form of carboxyl. It can only be deprotonated now to -COO- (Negatively charged). The -COO can not accept two protons. Just as the -NH3+ can not accept a 4th proton. This is determined by the atoms' valence and number of electrons
Very clear and concise. Thank you so much!
You're very welcome!
you're the best, thanks a lot.
Awwww, you're so welcome!
U just saved my life,Thank u
Glad I could help!
For the last example how does HN got to H3N
at what time?
Leah4sciMCAT I assume he means at 13:19 when you protonate the amino group
Wow you are amazing. I love it!
thank you
This is such a good explanation thank you!
You're very welcome!
this helped me on a biochem question, thank you
You're very welcome!
Thank you.You made it so simple
You're welcome
Very good explaination
Glad you like it!
Hi, thanks for the video. But why at pH13, amino group did not deprotonate?
You're welcome! It did deprotonate. Once it reached the pH of 13, it went from CH3NH3+ to CH3NH2. It lost a proton.
Really helpful. Thank you!
Thank you
It's so helpful! Thank you!!!
You're very welcome!
This is a very good explanation, thank you.
You're very welcome
Can someone answer this for me? I thought a molecule that has more H+ ions is BASIC and molecules that don't have that many H+ is acidic? Right or wrong?? for example which is the base and which is the acid of these 2......NaH2PH4 and NaHPO4 and why?
Have you seen my acid/base series? Leah4sci.com/acidbase
I love your explanation, it-s simply made and just enough :=)
Glad I could help!
Thx u so much! ❤
you're so welcome!
This was great! Thank you!
You're so welcome!
For pH of 13 for glycine, shouldnt the amino group be deprotonated and not protonated?
at which specific point in the video?
It is already deprotonated. Instead of H3N+, it has deprotonated at pH 13 to become H2N like she has drawn.
god bless you for this amazing video
thank you
i love this! Thank you very helpful
You're so welcome!
Shouldn't the amine on GLY be de-porotonated at pH 13 because pH>pKa? To go from neutral NH2 to NH??
Yes, the amine will be de-protonated at pH 13. It goes from NH3+ to a neutral NH2. The amine group will never be written as NH (and if it was, it would be negative in charge).
Thank you!!! You are a blessing 😍
you're welcome!
very, very helpful! Thank you so much!
You're welcome!
just wanted to clarify, at ph=13, the ph is greater than pka 9.6 of amino group, so amino group should be deprotonated to NH2 from NH3+ right? and thats why you get the charge on the amino group as 0?
At which specific part of the video are we talking about? (timestamp)
@@Leah4sciMCAT at time stamp 15:50
@Marissa Chukwu - correct.
You are so great! TY!
You are so welcome!
omg this makes a ton of sense
So glad it helped you understand!
Why is the amino acid Glycine represented with an NH group instead of an NH2 group, and the COOH group as the COO group?
I'm sorry but I don't offer tutoring through UA-cam 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/
thanks for a great video!
You're very welcome!
Omg you are a godsend god bless you
Wow, thanks!
So you said that the neutral form cannot exist, but that the zwitterion is the neutral form and then you claimed that it is the most common form, please elaborate I'm confused
I apologize for the confusion. The amine and carboxyl groups cannot both appear in their neutral form at the same time. In nature, we most commonly find amino acids as a zwitterion where the amine holds a positive charge and the carboxyl hold a negative charge. Overall, these two charges cancel out, creating a net neutral charge for the molecule. The idea is that neither group is neutral by itself, but together they form a net neutral molecule.
Thatssss really helpfullll thanks
You're very welcome!
LET HER COOK!!! wow, you just earned a subsciber!
Yay! Thanks so much for watching and subscribing! Glad you liked the video.
Just to clarify, does the pH look at the solution, while the pKa looks at the molecule?
I think you’ve got the distinction! The pH looks at the concentration of hydrogen ions in solution, while the pKa is a constant for any given molecule. The pKa gives us information about the acidity of a certain proton on the molecule and whether that proton will dissociate or not at the specified pH.
I have exams in 1hr, wish i saw this much before
Better late than never?
Bless you. I understand this well now :)
Awesome!
what if you are working with basic amino acid that is already carrying +1 charge?
I'm sorry, but I don't offer tutoring through UA-cam comments. 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/
Great video
Glad you like it!
Why do you have the Amine Group as "H2N" at the beginning of the video, but as "HN" at the end of the video?
Not sure I understand where you're seeing HN
on the amino group for the last exmaple
She drew H(space)N so that she eventually fills in all the numbers as she showed the specific pH values. Depending on the pH, the amino group is protonated or deprotonated, and she shows that with her drawings.
I really love you, thanks !!!
You're welcome!
Thank you so much !
You're very welcome
Do you give tutorials about other chapters of Biochemistry?
For the class or MCAT? My biochem resources are specifically designed for the MCAT. For more help with MCAT biochem, I recommend joining the MCAT study hall. Full details: join.mcatstudyhall.com/
Am confused, at 15:22, when you deprotonate NH2, shouldn't the charge become -1 instead of neutral?
NH2 is -1, but RNH2 is neutral due to having 3 bonds and 1 lone pair
Would you recommend memorizing the pKa values for all amino acids?
Yes and no. Only memorize the estimates I discuss here: leah4sci.com/amino-acid-charge-in-zwitterions-and-isoelectric-point-mcat-tutorial/
THANKU CUTIE
You're welcome
Thankyou very much mam...❤❤💖💖💖
You're welcome!
Can't thank you enough!
You're very welcome!
bless this video
Thanks! Good luck to you :)
Thank you so much
You're welcome!
THANK YOUUU!! I finally understood what to do if pKa is equal to pH! God bless you (//>^
You're very welcome! I'm so glad to help you understand!
at ph 13 why did the amine group get protanated ... is should be deprotonated ryt ? bcoz the surrounding has got less H+ ion they y did the NH was protonated ....im confused ..
+gandhi manikandan what point in the video?
+Leah4sciMCAT mam will the ammino acids we take in food are always in zwitter form ie amine is NH3 + and carboxyl group is coo - ??
+Leah4sciMCAT just nw watched ur vid again ..nw its clear just pls clarify the doubt above ...ie protein we eat has their ammino acids in zwitter form ? is it ?
Leah, do we need to memorize the pka of the R groups for the Acid Base A Acids for the MCAT? In those the range is +2- -2 correct?
Yes but not 'exact' values. Remember, on the MCAT close enough is good enough.
why is carboxylic is charge zero when pH is 1?
Thanks for asking! A pH of 1 is less than the pKa of the free carboxylic acid group (~2.3) on an amino acid. Because of this, the group will appear in its protonated form as -COOH and is neutral in charge.
i was confident until you did the example with glycine and misdrew it... it got me so confused during the entire example and now I'm just really anxious and confused :( ... please fix this....
at which point of the video are we referring to?
Excellent job Leah, thanks a lot! Just one question, regarding the quiz on your website: In part 3, we are asked to find the charge of Cys at PH = 4. Pka values for Cys are as follows: (Pka(COOH):1,71, Pka (NH2): 10,78, Pka(R): 8,33 ).
The solution suggests change 0 for the side chain. Could you please explain this to me? I would expect to see +1 for the side chain and not zero, as PH is much less than the Pka for side chain, which means that the side chain should get protonated (conveting to S2H+ from SH). Am I missing something? All help would be appreciated.
You're very welcome! Since I don't offer tutoring over social media, I would first suggest you use the download link at the bottom of the practice quiz to access the PDF quiz solutions.
If you would like a more detailed explanation, I recommend joining the MCAT Study Hall. For more details visit join.mcatstudyhall.com/ or contact me through my website leah4sci.com/contact/
at 12:47, would it be NH2 instead of NH? and O- instead of O? I'm just a bit confused on what the starting molecule of glycine looks like.
I was confused about this too! idk why she didn't explain this or make a note about it at least:(
Have the starting material as NH2 and COOH.. Remember NH2 can't be deprotonated further (to NH) and COOH can't be protonated further.
I’m sorry for the confusion and for the late reply. At no point does glycine actually exist with a single proton on the nitrogen or with an uncharged, de-protonated oxygen on the carboxy group. I simply had it appearing that way before I determined if either group was in its protonated or deprotonated form. There really is no “starting molecule” of glycine. It will exist at different charge states, depending on the pH of the surrounding solution. We always have to consider the pH before determining how glycine will appear.
I'm confused. Ka is a constant for any given acid, right? So how can it be proportional to the hydrogen concentration? Constants aren't proportional to things! Ahh!
Sorry you're so confused; let's get things cleared up for you.
Yes, Ka is a constant for any given acid. Maybe it would be better to say that Ka is proportional to the ratio of [H+]/[HA]. It stands to reason that acids which produce a higher quantity of H+ per unit of acid would have greater Ka values (and thus be more acidic). So even though the Ka doesn’t change for a given acid, it is variable between different acids based on how much H+ that particular acid produces.
Brilliant
Thanks!
You're welcome. I nailed the test😃😃😃.
That's amazing! So glad to hear it :)
Fantastic
Glad you liked it!
GOD BLESS YOU
Thank you for that!
here from anki deck
Glad to have you here!
It's not log, it's lg.
In the Henderson-Hasselbalch equation, we use a logarithm with a base of 10 which is abbreviated “log”.
Commonly used as log
I don’t know but why you are so concerned about acetic acid !!! Where is the amino acid in this whole lecture!!!!
An amino acid is an organic compound that contains both amine and carboxylic acid functional groups. In this video, I first look at acetic acid and methylammonium, as examples of how those same functional groups would behave on their own at various pH values. Then, to apply that knowledge, I turn to the example of the amino acid glycine at 12:37 to explain how these functional groups would function together within the same molecule at various pH values.
great explanation !! thank you ..
You're very welcome
thank you so much
You are welcome!