Myoglobin and Hemoglobin (Compare and Contrast)
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- Опубликовано: 12 июн 2024
- Moof's Medical Biochemistry Video Course: moof-university.thinkific.com/...
NOTE: Correction: The histidine that anchors the heme group is the PROXIMAL* histidine, while the histidine that helps O2 bind is the DISTAL* histidine. In the video, I mistakenly switched that. My apologies.
For Related Practice Problems with Worked Video Solutions on Protein Structure and Function, visit courses.moofuniversity.com.
In this video, I discuss the structures, functions, and key characteristics of myoglobin and hemoglobin, as well as compare and contrast the two.
Myoglobin (Mb) is a globular protein in muscle cells that functions in binding oxygen arriving to the muscles from the blood so as to deliver said oxygen to the muscle cells. Myoglobin has a single polypeptide chain with 8 alpha helices and no beta sheets. Since it has only one polypeptide chain, its highest level of protein structure is tertiary. It has one heme group (a prosthetic group) with an iron ion. It has two histidine residues in its interior, one of which is the proximal histidine, which anchors the heme group, while the other histidine residue, the distal histidine, helps myoglobin bind oxygen by reducing the binding affinity of carbon monoxide. Myoglobin’s oxygen binding curve is hyperbolic, characteristic of non-allosteric proteins.
Hemoglobin (Hb) is a globular protein in red blood cells that functions in taking oxygen from the lungs to the tissues (including muscle tissue) via the bloodstream. Hemoglobin has quaternary structure, as it is made up of 4 polypeptide subunits, two alpha subunits, two beta subunits, each of which can bind one oxygen molecule (each subunit has a heme group). Hemoglobin displays cooperativity, a form of allosteric regulation; essentially, once one oxygen molecule is bound to one subunit of hemoglobin, the affinity for oxygen at the other subunits increases. It becomes easier for each successive oxygen molecule to bind hemoglobin. Hemoglobin’s oxygen binding curve is sigmoidal, characteristic of allosteric proteins.
Between the two, Myoglobin has a higher affinity for oxygen than Hemoglobin. This can be see in their oxygen binding curves (shown in the video). This makes intuitive sense, though. If myoglobin functions by taking oxygen from hemoglobin in the blood to give to the muscle cells, then it MUST have a higher affinity for oxygen than hemoglobin. Otherwise, myoglobin wouldn’t be able to take the oxygen away from hemoglobin, and the muscle cells wouldn’t be able to be supplied with oxygen.
NOTE: Correction: The histidine that anchors the heme group is the PROXIMAL* histidine, while the histidine that helps O2 bind is the DISTAL* histidine. In the video, I mistakenly switched that. My apologies.
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This video is the video to go to about myoglobin and hemoglobin. You should become a professor. you teach things very systematically and easy to follow and thus understand! Thank you!
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I found this really helpful to watch! He talks about everything we covered in class and for me, listening and watching him write is a way better memory refresher than looking at my messy notes. I'm going to check out the other videos, for sure.
+Emma Collins Awesome! I'm glad you found it to be a helpful refresher, and I'm stoked that you plan to watch the other videos! Happy studying! :]
You are absolutely correct. Thanks for catching and noting that mistake. I've added an annotation and noted the mistake in the description for future viewers. Thanks again!
Your videos are a great platform for how teachers should distribute this kind of information.
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This video is very helpful, thank you very much! I'm just wondering if you have a video that goes into the structure of the heme for both haemoglobin and myoglobin?
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Amanda Mares You're very welcome! I'm happy to have helped!
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"and if you dont get any oxygen youll die. anyway, that wasnt very pleasant." haha i laughed out loud
+Sydney Alexander Hahaha! I just re-watched that part of the video, and I laughed out loud too.
me too...i just cant at that point
I have been watching you for years now :D
Quick question about distal and proximal histidines on the myoglobin. Shouldn't the distal one bind the oxygen instead of the proximal as you stated?
you talked about some pretty good points, i am satisfied
So correct me if I'm wrong, I'm told that if Myoglobin interacts with or merges with hemoglobin, renal failure will occur because the liver cannot process myoglobin to clean it. I'm told this is why car accident victims with massive damaged muscle tissue die of renal failure because of myoglobin getting into the blood stream. Is this correct? sorry for the long question.
This was so helpful!! Thank you!!
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Extremely helpful! Thank you!
It's very helpful. Thank you so much, sir.
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great vid man, stressin for this test tmr haha
Currently taking biochemistry.. Hopefully this video helps me!
That was really helpful and easy to follow :) .. Just one thing is that the distal histidine is the one stabilizing the binding of oxygen and the proximal one anchors the PPC to the heme not the other way around.
Amr, the correction was mentioned in an annotation in the video and in the description for the video as well. Cheers.
Hey, your video was very helpful thank you so much! However, you made a minor mistake at 6:44 where you mislabelled the functions of Distal His and Proximal His. Distal His are actually the ones responsible for reducing the binding affinity of CO and prevents the oxidation of Iron while proximal His are responsible for the anchoring of the heme via weak covalent bonds. Please correct if I'm the one making the mistake however, but I'm pretty sure I'm correct. All in all, your video was terrific!
Hey. You're definitely right. This was pointed out to me quite a while back, and I made an annotation noting the correction, which I put in the description. Thanks for pointing it out, and thanks for your kind words! I'm glad you found the video helpful! :]
you right proximal His BOUND to the iron and distal his form H-bonds with the bounded Oxygen to stabilize the bounded Oxygen
that really helped me to understand!! thanks
Rakan Alrufyadi Sweet! You're welcome!
Good informative video.
What happen if hemoglobin has greater o2 affinity than that of myoglobin? U explained it. But I think there is no problem to release of o2 by Hb and uptake of o2 by myoglobin. Because, release of o2 from Hb depends on Borh effect and these released o2 are then diffused into muscle cell and next bind with the myoglobin.
Is that graph you drew the Hill Plot?
your video is really helpful 😍😍😍please if you. can upload the equation or law of mass action of Hb and b 🙏🏻🙏🏻🙏🏻
thank you
this is very helpful
thank you so much. but, Who is the fastest transfer of oxygen please answer me 😧
thank you so very much.
Thank you, awesome job
Emily Asselin Sure thing, and thank you!
I think the distal and proximal histidines should be the other way around. The distal one is the one that helps oxygen bind.
very helpful video
I'm glad you found it helpful!
Thanks man!
Thank you so much
god bless your beautiful and amazing soul. I'm learning biochemistry
Thanks! I'm glad I'm helping you learn biochemistry! :]
Very helpful
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ismail from iraq
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Hey, the video doesn't work, I clicked on other videos on youtube and they worked but not yours.
King James That's really weird, dude. It's working for me. Try dragging to some place in the middle of the video, and hopefully it begins to play. If it works, you should be able to drag it back to the beginning, and all should be well.
Yes it's worked. Thanks for the amazing video. :)
King James Sweet! Sure thing!
my brain hurts
the video is not playin
never explains why the body chooses one over the other
Huh? What are you talking about?
As in the human body reaching the point of starvation, in its state of emergency begins to break down muscle for energy resulting in the production of myoglobin which broken down further becomes toxic to the kidneys. Take the story of the chilean miners for example, over half tested positive for myoglobin when they finally got to them. Which is one of the many reasons why some people want to know how and why it happens inside the human body and are extremely interested in comparing and contrasting with the body's natural healthy use of hemoglobin.
I think you're referring to rhabdomyolysis potentially leading to kidney failure. Though that does indeed involve myoglobin, that is not of critical importance to mention when simply comparing and contrasting hemoglobin and myoglobin to introductory biochemistry students. It's a more complex clinical correlate that doesn't exactly fit the purpose of this particular video, which is meant to introduce and explain the basics of protein structure and function.
You sound like a college professor gone wrong, insulated within your own self created bubble of information. There is nothing simple or basic about a protein structure or its potential relations with other chemical structures found in the human body. These biochemical proteins are literally an integral key to the stuff of life, at the very least one on a great list of universal mysteries. Attempting to over simplify them in front of others is the definition of ignorance.
Lol. Okay.
Awesome!!!!!!!! Thank you!!!!!!
Allison Bartlett Sure thing!!!!!