Blood gas transport Flashcards
What is the role of haemoglobin in oxygen transport?
To increase the amount of oxygen that can be transported within circulatory fluids this is done by it having a high affinity to oxygen.
What does the oxygen-haemoglobin dissociation curve show?
It shows how the partial pressure of oxygen in the blood affects its affinity to haemoglobin. It has a sigmoidal shape, as the partial pressure of oxygen increases the affinity increases until full oxygen saturation occurs where a plateau will form in the graph.
Where is haemoglobin most likely to load and off load oxygen in the body?
It will most likely load in an area of high oxygen partial pressure such as lungs.
And most likely to off load in an area of low partial pressure such as at respiring tissue
What is the Bohr effect?
When the afffinity of Hb to oxygen is affected due to a change in conformation. This has the effect of shifting the oxygen-haemoglobin dissociation curve to the right or left. This will potentially cause Hb molecules to realease or take on extra oxygen
Name other factors that affect the affinity of oxygen to Hb
PCO2 (Bohr Effect)
pH
Temperature
2,3-DPG (an intermediate of glycolysis, produced within red blood cells during anaerobic metabolism) concentration
What effects do these factors have on Hb?
Increased CO2, increased temperature, decreased pH (acidosis) and increased concentrations of 2,3-diphosphoglycerate decrease O2-Hb binding affinity by decreasing oxygen saturation at a given PO2 and effectively releasing O2 from Hb and visa versa.
Why are these condition helpful in the lungs?
The lungs have a high PO2, a low PCO2 causing a higher affinity of oxygen to haemoglobin allowing for higher oxygen saturation in the lungs.
Why are these condition helpful in resting tissue?
There is a lower PO2 therefore there is a lower affinity between O2 and Hb causing O2 to move from Hb to tissue.
Why are these conditions helpful in working tissue?
There is a very low PO2 so there is a high demand for O2, there is a higher PCO2 due to respiration causing a decrease in pH and an increase of 2,3 DPG this will reduce O2-Hb affinity causing more O2 to move from Hb to the respiring tissue.
What is anaemia?
A decrease in the number of red blood cells per unit of blood volume
What is anaemia caused by?
Decreased production of RBCs (e.g. iron deficiency) or rapid and excessive loss of RBCs (e.g. haemorrhage)
What is the effect of anaemia on the O2-Hb dissociation curve?
There is a decrease of number of Hb molecules but the affinity remains the same, this causes the curve to be lower than normal as the overall Hb content is lower.
What is carbon monoxide poisoning?
Carbon monoxide (CO) poisoning is a pathology that results from exposure to excessive levels of CO, a gas produced by incomplete combustion of fossil fuels when oxygen levels are deficient.
What effect does CO poisoning have on Hb?
CO displaces O2 at Hb binding sites, as it binds with much greater affinity. As binding sites are occupied by CO, less O2 can bind and so less is transported. Therefore the total O2 content of the blood will decrease, as will the concentration of oxyhaemoglobin.
What effect does CO poisoning have on the O2-Hb dissociation curve?
The overall concentration of Hb in the blood remains constant. Firstly there is a slight increase in O2-Hb affinity is observed in CO poisoning, as CO inhibits the production of 2,3-DPG, shifting the curve to the left then the curve saturates at a lower oxygen content.
