HEMOGLOBIN AND MYOGLOBIN BIOCHEMISTRY

Myoglobin and hemoglobin are oxygen-binding proteins. Hemoglobin is found in blood, and myoglobin is abundant in skeletal and cardiac muscle. Hemoglobin is an oxygen-transporter, and myoglobin is an oxygen-storer.
Myoglobin is a globular protein made up of a single polypeptide chain. Hemoglobin is also a globular protein, but it is a tetramer and is composed of 4 polypeptide chains. It is an α2β2-type tetramer, with two identical α chains and two identical β chains. Each of hemoglobin’s four subunits is very similar to the polypeptide chain making up myoglobin.
The myoglobin polypeptide chain consists of 8 α-helix sections, which are denoted A-H. Each polypeptide chain of the four hemoglobin subunits also consists of these 8 alpha-helix sections. Between these helices are connecting regions named after the helices they connect - e.g. AB region. Amino acids in each helix section are numbered - e.g. His F8.
Both myoglobin and hemoglobin have a prosthetic group. The prosthetic group found in both myoglobin and hemoglobin is the heme group, made up of a protoporphyrin ring and a central iron atom.
There is a heme group in each of hemoglobin’s subunits, as well as in myoglobin’s polypeptide chain, in the cleft between the E and F helices.
Iron can interact with 6 ligands, and four of these are provided by the nitrogen atoms of the pyrroles in the porphyrin ring. A fifth is provided by the imidazole side chain of His F8. When oxygen binds to the iron, that is a 6th ligand! Note that when oxygen is added on, it is tilted at 60° to the perpendicular.
A really cool conformational change happens when oxygen binds to the iron in the heme group. This cool phenomenon is of no consequence in myoglobin, but hemoglobin’s biological function depends on it. Before the binding of oxygen, steric constraints result in the ferrous iron lying 0.055 nm above the porphyrin plane. The binding of oxygen causes the iron to be drawn into the plane of the porphyrin ring, so that it is only 0.026 nm above it. The movement of the iron drags His F8 along with it and sets off a chain of conformational changes in hemoglobin that results in increased affinity of the heme groups of adjacent subunits for oxygen.
In hemoglobin, the four subunits - the two α subunits and the two β subunits - are arranged into two dimeric halves - one α1β1-subunit pair and one α2β2-subunit pair. Each of these dimeric halves moves as one rigid body. Subunits interact mostly with dissimilar chains - in other words, α subunits interact with β subunits, but not α subunits, and β subunits interact with α subunits, but not β subunits. There are two types of contacts between the two dimeric halves of hemoglobin - packing contacts and sliding contacts. Packing contacts do not shift during the conformational changes that occur after the binding of oxygen, while sliding contacts do.
When oxygen binds, the conformational change results in the dimeric halves rotating 15° relative to one another. Hemoglobin’s two conformations are called the T (for tense or taut) and R (for relaxed) forms. When hemoglobin is in the T form, oxygen is only accessible to the heme groups of the α-chains. Steric hinderance prevents it from binding to the chains. This steric hindrance is not present in the R conformational state. Hemoglobin resists oxygenation because its deoxygenated form, the T form, is stabilized by certain hydrogen bonds and interchain salt links. These interactions are broken in the oxygenated form, the R form, where hemoglobin is stabilized in a different conformation.
Meanwhile, myoglobin does not easily release oxygen. When myoglobin binds oxygen, it becomes oxymyoglobin. Oxymyoglobin releases oxygen during times of extreme oxygen deprivation, like when you’re exercising.
While Myoglobin’s O2-binding interaction displays classical Michaelis-Menten-type saturation behaviour, Hemoglobin’s interaction results in a sigmoid-shaped curve rather than a hyperbolic one. The sigmoid shape allows us to draw some conclusions. Binding of oxygen to one subunit of hemoglobin strongly enhances binding of oxygen to other subunits - a phenomenon called cooperativity.
Hemoglobin binds oxygen in the lungs, where the partial pressure of oxygen is around 100 torr. Here, 98% of hemoglobin has oxygen bound to it. In the capillaries of some tissues, the partial pressure of oxygen is 40 torr, and the hemoglobin releases oxygen. Here, 6% of hemoglobin has oxygen bound to it. The 92% difference is thanks to cooperativity. If hemoglobin’s curve was hyperbolic, then only 79% of hemoglobin would have oxygen bound in the lungs, and 28% of hemoglobin would have oxygen bound in the capillaries, for a difference of 51%. So the cooperativity means that hemoglobin is… 92/51% = 1.8 times more efficient at delivering oxygen!
MYOGLOBIN 3D MODELS: 3dprint.nih.gov/discover/3dpx-000200
3dprint.nih.gov/discover/3dpx-000201

[@fizzakhalid4780]

Medical students really need these kind of short animated videos...as they hardly get time for long 1 hour lectures...my appreciation for your smart work..keep going like this

[@nicks.3181]

Biotechnology Students approve that 🤝

[@vladabalinsky7276]

Thank you for explaining the more complicated, in-depth concepts such as HOW the hemoglobin changes shape, instead of just saying that it does. SUPER helpful.

[@JB23669]

Literally the definition of high yield thank you so much!

[@aliuy8184]

Just about 6 minutes of a very substantial discussion. The 2hr class lecture can never lol Amazing job!

[@Kevin-sy8uf]

Son of a gun! this is some next level sauce

[@Mistfall254]

IKR

[@okoyes7151]

What

[@alixzandrazabal1671]

YEP!

[@19tomed72]

Thank you for such a great, in-depth explanation for all us medical students!

[@afjuneek9536]

This really simplified everything Your way of explaining makes it all so easy to understand Thank you

[@donnaozgur5761]

Didn't know that I could learn so much and in an easy way in only 6 minutes. Thank you!

[@richardshaw6664]

Wow, this 6 minute review took me back 15 years ago to grad school struggles to learn this stuff. Excellent!

[@lanahamerlitz5926]

Fenomenal video!!! You just made it perfectly clear for me, my teacher couldn’t do that in two hours while speaking about it

[@mollyhorse]

Absolutely brilliant video!...seriously can't thank you enough!!!!! It took you 4 minutes to explain what my lecturer has tried to do in 4 2 hour lectures!

[@sadhgurusshortvideos6265]

Omg!! That's the best explanation of this topic on KZbin 🤩🤩

[@davidtrongnguyen]

WOW! Incredible how you can explain this concept and make it so easy to understand. THANK YOU!

[@mockingjaypin]

this was very well explained and animated! thank you so much, this really helped me.

[@Callmeromain2016]

This is the best explanation of this topic on the internet :)

[@pranatisingh7168]

Such a beautiful video, couldn’t have been better❤️

[@jackrutledgegoembel5896]

incredible video! Thanks so much! I love that people put stuff out like this, it really does the world a service.

[@hughgeary7356]

Just stumbled on your videos as I'm going through an online, at your own pace, biochemistry class. This was very helpful, thank you!

[@NeuralAcademy]

I'm so glad to be of help ^_^ Thank you for your kind words! :-D

[@ilikelivemusic]

Wow, what an amazing and clear explanation. THANK YOU!

[@elizabethkim1558]

This is fantastic! Such a great resource. You summarized a day's worth of lecture :')

[@sophiathomas9732]

Priceless.....Excellent one......Crystal Clear..God bless you

[@necla3674]

Great video! Thank you for helping us out! I wouldn’t understand without you👍

[@thomasbulliard39]

Really good job and deep explanation ! It's always difficult to find some explanations going so far. Most of the time it's too general: Thank you ;)

[@NeuralAcademy]

Thanks! I do my best to go as in depth as possible while keeping the videos to a reasonable length :-)

[@sathisarkar7589]

such a vast topic covered in such a brief and magnificent way!!...thanks so much !!

[@leylaa3259]

SUCH A GOOOD VIDEO, THANK YOU!

[@alyssapuga288]

This was amazing. THANK YOU SO MUCH I DIDNT EVEN REALIZED I WAS AS CONFUSED AS I WAS. Can you teach my biochem class instead???!?

[@mollyhorse]

Haha...that's what I was thinking,Alyssa!

[@kingbobbie5196]

I know right 😅😅

[@minoliedirisinghe3727]

This is the best video i get about haemoglobin😍

[@lana89001]

Honestly. Reading from the book made me so confused!! And now everything is so clear! It’s way more easy to understand from this video.

[@alexrodriguez123430]

Best video I've seen on this yet!!

[@jyothirmaisunkari6662]

Thank you for making us to understand the complicated topics in a easy way😊.

[@clayric4825]

This video just helped me become a doctor. Thank you sir

[@neuron4649]

Thank you so much for the video. Your way of explaining makes it really easy to understand.

[@briannal.7657]

This is a great video!! Thanks so much!!

[@lancemaxwell8464]

Thank you so much for this, really cleared the confusion i had about these two before my biochemistry final

[@smighty]

this is the shortest high yield video i have ever watched, thank you

[@saikatsen391]

Really good and very nicely explained.I'll recommend this video to my students. #Thanks a lot# from Bengaluru, India.

[@houmamkitet9555]

That was so well made, thank you so much for your hard work

[@Ray-238]

Thank you SO MUCH! This was extremely helpful and explained really complex ideas.

[@bonbon0416]

Excellent! Thank you. ❤

[@fitsumbelayneh4559]

Such a wonderful video I have been looking for, thanks

[@doctortabby]

Excellent presentation. Thank you.

[@maxmahmood100]

Great video as always!

[@emeralds3392]

Thank you very much .. your explanation is excellent

[@jofinaonecopy2399]

Thanks for your precise video

[@Michelle-hn8ob]

Thanks so much for this explanation!

[@brynnh4369]

New subscriber this is so great thank you

[@dhabyaahmed8134]

That was great. Thank you very much!

[@Finisch43]

Great work !

[@geoffreymaibohm700]

This is amazing!

[@hinamushtaq1757]

You made my all doubts clear ... thanks

[@justrovshan]

U were made for it, thank u👏👏👏👏👏

[@halimahassib6930]

You aaree thee bestt channel everr.. Thaaank u so muuch ❤️❤️

[@startingpointformedicose1731]

Wow.. can't even think that this topic was soooo much confusing for me before. Make more videos on second year biochemistry too😊

[@madhu.s1595]

I was so confused..... as I was studying from books only n notes just imagination.... Now I see the animation n got the concept... Clear.... Thanks for your efforts.... 🙏🙏

[@salma5266]

U are amazing. Thank u so much !

[@horacefields736]

Very good explanation. Thank you

[@theofficialblob]

this is amazing!! i finally understand!! great job

[@saikeerthanarachamadugu8171]

Superb sir.. U have explained big biochemistry concept in just few minutes and thank you for making such videos

[@toobaghummanghumman5760]

It is top class lecture....

[@snehakumarijha8314]

Thanks a million!

[@mohakjain2005]

excellent video sir I am so inspired that I have got into the glory of this life love you and your work sir always reign and inhabit this world #Bio2U Classes

[@amnie]

Amazing !

[@dr.baleeghwsaby8829]

شكرا جزيلا لك يا دكتور

[@Megaredronin]

omg i think i just had a nerdgasm!! bloody amazing!! i love it!! :)

[@azharmehmood6515]

Well explained ...thanku sir

[@ssui6892]

Very professional explanation!

[@skate1]

Thanks I just remembered why I quit nursing

[@tanvirvai7201]

thank you for the nice explanation

[@dr.ds.linghampillai283]

Awesome to know the difference for better knowledge

[@Maria-sf8yg]

thanks that was really helpful

[@madeleines3092]

this is awesome, i can't thank you enough!!

[@clarencechoy2382]

Sums up my 2-hour long lecture lol. Thanks!!

[@shannonladiana502]

My short attention span is killing me rn but this def saved me!!

[@mayanksangam9205]

This helped a lot. Thank you:)

[@jyotikumari-vc4ep]

Very helpful, thanx

[@haroonhamid5352]

ridiculously good video

[@meleyna9138]

Love it 💜 thanks

[@samuelstringer1460]

great vid

[@The-advicer]

Love it ❤

[@user-dp8ku2ue5i]

Marvellous❤❤

[@mohamedmouh3949]

thank you very much

[@subhani9501]

Amazing

[@sccm100]

Great video! High yield!

[@faemaahamed8080]

Very beautifully presented

[@wiamalbouzidi8362]

Thank you !

[@fatemehsoltani5457]

perfect. thanks

[@adhipmitra]

Awesome.

[@srishtichatterji945]

Thanks for the video! does the concentration of hemoglobin affect the ability of myoglobin to bind oxygen?

[@subhadipdas2482]

Good effort 🔥

[@sara-hh3ts]

thank you so much!

[@nighatgull6116]

Thank u so much

[@PunitKumar-kd5nk]

Life saving video

[@nanoroutes9849]

Thank you so much sir

[@sameepsapkota4615]

Wow wow wow This is pure gold

[@afsaneheghbali3987]

I would appreciate it if you could talk about the fisher hypothesis on the respritory system

[@everytimesummertime]

thank you!

[@rebeccabates4673]

Awesome!

[@user-is8ee5gk7k]

It was really helpful

[@nehibroadcasting]

Great videos! Will you please publish a series of videos on laboratory techniques in cell biology labs. Thanks

[@ur1299]

damn! this is some next level stuff