HEMOGLOBIN AND MYOGLOBIN BIOCHEMISTRY
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- Опубликовано: 28 сен 2024
- 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.go...
3dprint.nih.go...
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
Biotechnology Students approve that 🤝
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.
Literally the definition of high yield thank you so much!
Son of a gun! this is some next level sauce
IKR
What
YEP!
Wow, this 6 minute review took me back 15 years ago to grad school struggles to learn this stuff. Excellent!
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 ;)
Thanks! I do my best to go as in depth as possible while keeping the videos to a reasonable length :-)
Just about 6 minutes of a very substantial discussion. The 2hr class lecture can never lol Amazing job!
This really simplified everything
Your way of explaining makes it all so easy to understand
Thank you
Just stumbled on your videos as I'm going through an online, at your own pace, biochemistry class. This was very helpful, thank you!
I'm so glad to be of help ^_^ Thank you for your kind words! :-D
Really good and very nicely explained.I'll recommend this video to my students. #Thanks a lot# from Bengaluru, India.
BRUV, YOU'VE JUST PUT MY BIOCHEM PROFESSOR TO SHAME. TOOK YOU FIVE MINUTES TO EXPLAIN HIS TWO 50 MINUTE LECTURES ABOUT GLOBINS LMAO.
Fenomenal video!!! You just made it perfectly clear for me, my teacher couldn’t do that in two hours while speaking about it
WOW! Incredible how you can explain this concept and make it so easy to understand. THANK YOU!
This is the best video i get about haemoglobin😍
Thanks I just remembered why I quit nursing
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.
This is fantastic! Such a great resource. You summarized a day's worth of lecture :')
Priceless.....Excellent one......Crystal Clear..God bless you
this is the shortest high yield video i have ever watched, thank you
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???!?
Haha...that's what I was thinking,Alyssa!
I know right 😅😅
Thank you so much for the video.
Your way of explaining makes it really easy to understand.
Such a beautiful video, couldn’t have been better❤️
Thank you for making us to understand the complicated topics in a easy way😊.
incredible video! Thanks so much! I love that people put stuff out like this, it really does the world a service.
Best video I've seen on this yet!!
Excellent! Thank you. ❤
Great video! Thank you for helping us out! I wouldn’t understand without you👍
شكرا جزيلا لك يا دكتور
Awesome to know the difference for better knowledge
Thanks for your precise video
This is a great video!! Thanks so much!!
That was great. Thank you very much!
SUCH A GOOOD VIDEO, THANK YOU!
Great work !
Do courses in unis mention anything about complex ion, dative covalent bonds, ligands etc? basically a bit more chemistry insight
This is amazing!
Thanks a million!
Thank you very much .. your explanation is excellent
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
You aaree thee bestt channel everr.. Thaaank u so muuch ❤️❤️
Well explained ...thanku sir
Marvellous❤❤
ridiculously good video
Life saving video
Thank you SO MUCH! This was extremely helpful and explained really complex ideas.
Amazing !
I would appreciate it if you could talk about the fisher hypothesis on the respritory system
thank you በጣም እወድሀለሁ
Very helpful, thanx
Very professional explanation!
Thankyou so my sir
great vid
Amazing
U are amazing. Thank u so much !
Kindly make lecture on lipoprotein metabolism
Thanks so much for this explanation!
thank you very much
this is amazing!! i finally understand!! great job
Thank you so much sir
Love it ❤
perfect. thanks
You try to give the video more brightness it will be great if you do
Great
now a i know a lot more stff than i was lookinmg for
this is awesome, i can't thank you enough!!
Great video! Pls can you explain how the pO2 exactly contributes to the sigmoidal shape of the hemoglobin function? Thank you
As pO2 increases, more heme groups will have coordinated with O2 molecules. Because of cooperativity between the Hb subunits, having some O2 bound will increase the affinity of the other subunits for O2, resulting in that exponential behavior for the first part of the curve. As the hemoglobins become saturated with O2, we begin to taper off, giving us a logarithmic/hyperbolic behavior, which together with the exponential 1st half forms a sigmoidal curve.
Great video.. Can you elaborate on Tense and Relaxed forms please?
First time I've heard so many words and didn't understand one!
good deal, so the myoglobin is causing micro clots?
super sir
Structure of myoglobin and hemoglobin are same or not ?
@2:53 you meant to say ' chain of conformational changes in the adjacent "myoglobins" '?
Wow wow wow
This is pure gold
Could you do a video on protein folding?
These are some cool stuff to spend time on, rather than some those BS on tiktok en reels lol
Great videos! Will you please publish a series of videos on laboratory techniques in cell biology labs. Thanks
Plz told that the name two respirators that carry oxygen?
Love it 💜 thanks
i like it, good explanation, packaged chromosomes? as hemoglobin or the nucleus of a cell, how many myoglobin's?
Very good video but it ia ganna be nice if your take caption for arabic language in the next video
thank you so much!
The more of this sort of information I am exposed to, the more confirmed I am in my opinion that, honestly, no one actually believes that this all slowly, incrementally cobbled itself together over billions of years. The very thought of it is patently absurd on its face. And just think what a crude, extremely simplistic representation of the actual dynamic reality this graphic is. ‘Life’ is utterly mind boggling.
scientists agree that we evolved through natural selection. See more videos on evolution if you still don't understand it.
Awesome!
damn! this is some next level stuff
good
top !!!! dommage qu il n y a aucune video francaise un peu pret corect sur ce teme
Vous pouvez essayer les sous-titres traduits automatiquement en français. Salut du Canada!
It was really helpful
thank you!
Good effort 🔥
Why my hemoglabin is not work when i sleep then i wake up it is work faster .couse ibleeding after whisper or after use a comfort room.
Very good, thank you. One remark: the calculation at the end cannot be correct.
🙌❤
Greaaaaaaaaaaaaaat ♥ ♥
Good introduction to hemoglobin & myoglobin. It would be much better if electronic, geometric & magnetic aspects of dioxgen binding are covered.
This is a biology covering functional inorganic chemistry concepts. If you want to see mechanics of bonding, look for a chemistry video
So as we know O2 cannot be released by hemoglobin WITHOUT THE PRESENCE OF CO2... why is this not mentioned?
I just thought to myself when was the gene for hemoglobin and myoglobin created? Meaning, through evolution and gene-duplication, the two genes separated into their current modern configurement. Comparative sequence analysis has shown that vertebrate myoglobin and hemoglobins diverged from one another about 450 million years ago.
So essentially what this shows is even after 450 million years, these genes are extremely similar, which makes sense as oxygen use genes would need to be highly conserved. Conserved means that they cannot change that much without losing their function as if they lose their function, whatever creature needs them will die immediately after the creation of the gamete as they will not be able to use any oxygen due to the heme/myoglobin being defective.
like sir
this guy sounds like Nile red, does all chemists sound like that?
I have to play this video again 🩸🩸🩸
Eski ppt mil skti h kya