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1. Introduction to biochemistry
- Prof. Gerald W. Feigenson
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2. Amino acids and peptides
- Prof. Gerald W. Feigenson
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3. Protein structure principles
- Prof. Gerald W. Feigenson
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4. Observed protein structures
- Prof. Gerald W. Feigenson
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5. Protein folds and IV structure
- Prof. Gerald W. Feigenson
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6. Protein stability and folding
- Prof. Gerald W. Feigenson
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7. Haemoglobin structure and stability
- Prof. Gerald W. Feigenson
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8. Enzyme specificity and catalysis
- Prof. Gerald W. Feigenson
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9. Enzyme kinetics (Michaelis-Menten)
- Prof. Gerald W. Feigenson
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10. Enzyme inhibition; chymotrypsin
- Prof. Gerald W. Feigenson
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11. Enzyme regulation and coenzymes
- Prof. Gerald W. Feigenson
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12. Lipids, biomembranes and membrane proteins
- Prof. Gerald W. Feigenson
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13. Structure and function of carbohydrates
- Prof. Gerald W. Feigenson
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14. Metabolism principles
- Prof. Gerald W. Feigenson
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15. Glycolysis - energy and useful cell chemicals
- Prof. Gerald W. Feigenson
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16. Glycolysis control
- Prof. Gerald W. Feigenson
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17. Metabolism of pyruvate and fat
- Prof. Gerald W. Feigenson
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18. Urea cycle; oxidative phosphorylation 1
- Prof. Gerald W. Feigenson
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19. Urea cycle; oxidative phosphorylation 2
- Prof. Gerald W. Feigenson
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20. Light-driven reactions in photosynthesis
- Prof. Gerald W. Feigenson
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21. Gluconeogenesis and the Calvin cycle
- Prof. Gerald W. Feigenson
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22. Synthesis of lipids and N-containing molecules 1
- Prof. Gerald W. Feigenson
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23. Synthesis of lipids and N-containing molecules 2
- Prof. Gerald W. Feigenson
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24. Hormone mechanisms
- Prof. Gerald W. Feigenson
Printable Handouts
Navigable Slide Index
- Introduction
- Lecture outline
- Transport proteins: properties of O2 carriers
- Comparison of Mb and Hb
- The special properties of Hb
- Binding of O2 by Hb: the sigmoid curve
- The Hill equation (1)
- The Hill equation (2)
- Salt bridges of deoxy-Hb not found in oxy-Hb
- Deoxy-Hb has additional stabilisation
- Why would O2 binding disrupt distant ion pairs?
- How different IV can change Hb's affinity for O2
- The Bohr Effect = H+ - induced release of O2 (1)
- The Bohr Effect = H+ - induced release of O2 (2)
- Foetal vs. adult Hb: another ion-pair story
- Two models describing changes in O2 binding affinity
- Lecture summary
Topics Covered
- Myoglobin vs. haemoglobin
- T-state and R-state of haemoglobin
- Haemoglobin affinity for O2
- The Bohr effect
- Two models for O2 binding affinity
Talk Citation
Feigenson, G.W. (2022, November 27). Haemoglobin structure and stability [Video file]. In The Biomedical & Life Sciences Collection, Henry Stewart Talks. Retrieved October 5, 2024, from https://doi.org/10.69645/NKXM2506.Export Citation (RIS)
Publication History
Financial Disclosures
- Gerald Feigenson has no commercial/financial relationships to disclose.
Request access to the Principles of Biochemistry lecture series, an extensive introductory to the field of biochemistry. An HSTalks representative will contact you with more information about this series and getting unrestricted access to it.
A selection of talks on Biochemistry
Transcript
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0:00
Hello, and welcome to this Principles of Biochemistry lecture series.
My name is Jerry Feigenson,
I am a professor in
the Department of Molecular Biology and Genetics at Cornell University in the USA.
In the sixth lecture,
you saw that proteins are thermodynamically stable,
but most are not very stable.
All information for the folding pattern is contained in the amino acid sequence.
However, it is not at all clear how
proteins can possibly fold up as fast as they actually do.
Many proteins tend to misfold and therefore need some help.
Proteins exhibit various types of motions.
0:47
In this lesson, you will learn that haemoglobin shows a sigmoid curve of oxygen binding.
That haemoglobin has two different stable quaternary structures
called the T- state and an R-state.
The general principle of protein quaternary structure
being tensed or relaxed was first discovered for haemoglobin.
The haemoglobin T-state is stabilized by many pH-dependent ion pairs.
1:20
What's the role of the haem group?
Well, you previously saw that the myoglobin protein
is shaped to fit the haem group and hold it in a crevice.
But here, let's consider what would be the ideal properties of a molecule
designed to pick up oxygen in the lungs and then deliver oxygen to the tissue.
We can make a graph of the fraction of haem groups that have an oxygen bound,
and we call that fraction theta.
We will graph theta against the oxygen pressure.
Really, we should graph theta against the oxygen concentration,
but that's hard to measure.
So we measure oxygen pressure.
So we'll make this plot for myoglobin.
We see that there's a pressure of oxygen in
the lungs and there's a much lower pressure in oxygen starved tissue.
For myoglobin, at the oxygen pressure in the lungs,
myoglobin is saturated with oxygen,
so it meets that criterion of a molecule designed to pick up the oxygen.
But there's another criterion, and that is,
the molecule must give up the oxygen to where it is needed - oxygen starved tissue.
Myoglobin does not do that.
Myoglobin is still holding its oxygen in oxygen-starved tissue.
So myoglobin is far from ideal as a molecule to pick up oxygen and then drop off oxygen.
Now let's look at haemoglobin.
So haemoglobin has a different shape of oxygen binding curve.
It drops off a considerable fraction of its oxygen when it reaches oxygen starved tissue.
We call this shape of the oxygen binding curve sigmoid or S-shape.
But we use the term sigmoid.