Haemoglobin and Oxygen dissociation curves Flashcards
Describe the structure of hemoglobin?
1-Primary Structure:
4 polypeptide chains
2-Secondary Structure:
Each polypeptide chain is coiled into a helix
3-Tertiary Structure – Each chain is folded into a precise shape
4-Quaternary Structure :
4 chains are linked together to form a ~ spherical molecule.
Further, describe the quaternary structure?
1-Each polypeptide chain has a haem group
2-A haem group has an iron ion (Fe2+)
3-Each Fe2+ can join to an Oxygen molecule
(O2)
4- Total = 4 Oxygen molecules can be carried by 1 hemoglobin molecule in humans
What is the haem group in hemoglobin?
a non-protein component of haemoglobin which is made up
of a prosthetic porphyrin ring with an iron ion centre (Fe2+)
How is oxygen carried around the body?
in RBC, which contain the
molecule hemoglobin
What is formed when oxygen and hemoglobin join together?
What’s the word reaction?
oxyhemoglobin
Haemoglobin + oxygen oxyhaemoglobin
what is oxygen saturation?
How is it expressed?
What levels of saturation does the blood leaving the lungs have?
What does 100% saturation have?
What does 50% saturation have?
the amount of oxygen bound to the
hemoglobin in our blood,
———————————————
expressed as a percentage of the
maximum, The units are SaO2%
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saturation of 95-99%.
——————————–
means the hemoglobin is carrying its maximum amount of oxygen (4 atoms oxygen per hemoglobin molecule)
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it is only carrying half of what it could carry. (2 atoms oxygen per hemoglobin molecule)
What’s the role of hemoglobin?
What must it do?
How does oxygen dissociate from hemoglobin?
to transport oxygen
Easily associate with oxygen at the gas exchange surface
and
Easily dissociate from oxygen at the tissues that require it
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The shape of hemoglobin changes slightly under different conditions
With increasing Carbon dioxide, haemoglobin’s shape makes it
bind more loosely to O2 , so it loses the oxygen more easily – it dissociates more readily.
What is the loading of oxygen and where does it occur?
What is the unloading of oxygen and where does it occur?
haemoglobin combining
(associating) with oxygen
lungs
———————————-
hemoglobin releasing
(dissociating) with oxygen
tissues
Why doesn’t Haemoglobin absorb oxygen evenly when exposed to different partial pressures?
1-Very low concentration of oxygen: the 4 chains in the haemoglobin are very closely united, making it difficult
to load the first oxygen molecule
2- Once one Oxygen molecule is loaded, the oxygen causes
the remaining chains to load the other oxygen molecules
more easily
What does it mean when the sigmoid curves shift to the left?
What does it mean when the sigmoid curves shift to the right?
Higher affinity for O2
Lower affinity for O2
Does fetal hemoglobin have a higher affinity for oxygen than adult hemoglobin?
if yes then why is it important?
yes
it means fetal haemoglobin will load oxygen when adult hemoglobin is unloading it
What is the Bohr effect?
In the presence of an increased concentration of Carbon
Dioxide where does the Oxygen
dissociation curve?
How the concentration of Carbon Dioxide in the blood effects
the dissociation curve
——————————-
shifts more towards the right
Why does the Bohr effect occur?
1-Carbon dioxide reacts with water forming carbonic acid
2-The enzyme carbonic anhydrase catalyzes this reaction H₂CO₃ dissociates into HCO₃̄ and H⁺
The H⁺ is picked up by the Haemoglobin molecules which then
release their O₂
3-The HCO₃̄ diffuses out of the RBC and enters the plasma. Cl ̄diffuses in to balance the charges.
How does Bohr effect explain behaviour of haemoglobin in the
lungs?
In the lungs, the level of carbon dioxide is low because it diffuses across the surface and is breathed out. So, hemoglobin has a higher affinity for oxygen (there is also a higher concentration of oxygen in the lungs). This means oxygen is readily loaded by hemoglobin.
How does Bohr effect explain behaviour of haemoglobin in the
muscles?
In the muscles the level of carbon dioxide is high because it is produced by respiration. So, haemoglobin
has a lower affinity for oxygen (there is also a lower concentration of oxygen in the muscles). This means
oxygen is readily unloaded by haemoglobin.
