Lecture 4 - Oxygen In The Blood Flashcards
What criteria must an oxygen carrier meet?
Reaction must be reversible
Carrier must associate with O2 at lungs but dissociate at tissues
Describe the structure of haemoglobin:
Made of 2 alpha and 2 beta subunits
Each subunit has 1 haem group
Each haem group can bind 1 oxygen molecule
How many oxygen molecules can a single Haemoglobin molecule transport?
4 oxygen molecules
What is cooperativity in terms of haemoglobin?
The change in haemoglobins affinity for oxygen as it changes shape
What are the 2 stages of affinity for haemoglobin?
T state (tense state)
R state (relaxed state)
What is the T state (tense state)?
When no oxygen is bound to haemoglobin it has a very low affinity for oxygen
What is the R state (relaxed state) of haemoglobin?
Once the first oxygen has bound it has a higher affinity for oxygen, as more and more oxygen binds the affinity for oxygen increases
What shape of curve is the haemoglobin-oxygen dissociation curve?
Sigmoidal curve
What is the relative partial pressure of oxygen in venous blood compared to arterial blood?
What affect does this have on haemoglobin?
pO2 in venous blood is low compared to arteries so highly saturated Hb will give up oxygen
What is considered a normal oxygen saturation?
95% or above
What is O2 saturation?
The percentage of haemoglobin that is saturated with O2
What 3 substances promote the release of O2 by shifting the equilibiurm to the deoxygenated form of haemoglobin (T state)?
H+
CO2
2,3-Diphosphoglycerate (2,3-DPG)
How does metabolic acidosis affect Haemoglobin-oxygen dissociation?
How does it affect the sigmoidal curve?
Metabolic acidosis means lots of H+ in blood
H+ encourages dislocation of oxygen from oxyhaemoglobin
More H+ shifts the oxygen dislocation curve to the right since a higher partial pressure of O2 will be needed to get the same level of saturation than if there was no extra H+
How are people living in high altitudes (with low pO2) adapted to maximise gas exchange?
High capillary density
What is Hypoxaemia?
When there’s a low partial pressure of O2 in arterial blood
What is hypoxia?
When the oxygen levels are low relative to the need in the body or tissues
So tissues using O2 faster than its delivered
What is the difference between hypoxaemia and hypoxia?
Hypoxaemia is when the partial pressure of O2 ini arterial blood is low
Hypoxia is when oxygen levels are low relative to the bodies demand
How is the blood composition affected by anaemia?
Reduced amount of haemoglobin in blood
How does oxygen saturation in the blood of a normal person compare to that with a person with anaemia?
Oxygen saturation is the same since there is no haematological problem with the haemoglobin so any haemoglobin available still gets saturated like normal theres just less of it
What does a shift to the left in the oxygen dislocation curve indicate in terms of Hb affinity?
What does a shift to the right in the oxygen dislocation curve indicate in terms of Hb affinity?
Left = increase haemoglobin affinty for oxygen since lower partial pressure of O2 needed to fully saturate Hb
Right = decreased haemoglobin affinity for oxygen since higher partial pressure of O2 needed to fully saturate O2
How does 2,3-diphosphoglycerate affect haemoglobins affinty for oxygen?
It decreases its affinity fo oxygen by binding to the beta chains
How does temperature affect haemoglobins affinty for oxygen and why?
At higher temperatures Hb affinity for oxygen is less
In highly metabolically active tissues temperature is high, these tissues need oxygen so the Hb has a decreased affinty for oxygen so it gives it up for these tissues
What is the Bohr effect?
H+ levels and pCO2 levels are high the affinity of Hb for O2 decreases so it gives up O2 more easily (levels of these are high around highly metabolically active tissues)
What is the Haldane effect?
Deoxygenated Hb has a higher affinity for CO2 due to Allosteric modulation of CO2 binding sites
