Oxygen transport in the blood Flashcards
(22 cards)
What is Henry’s law of partial pressures?
The amount of a given gas dissolved in a given type and volume of liquid at a constant temperature is proportional to the partial pressure of the gas in equilibrium with the liquid
How is most (98.5%) oxygen transported in the body?
Bound to haemoglobin
What is contained in a molecule of haemoglobin?
2 alpha and 2 beta subunits each containing a haem group, each of which can bind reversibly to one molecule of oxygen
In what saturation level is haemoglobin at, at low pO2?
Low saturation
In what saturation level is haemoglobin, at high pO2?
High saturation
What does the saturation - Blood pO2 graph look like?
What is the equation for Oxygen delivery index (DO2I)?
DO2I = Oxygen content of arterial blood (CaO2) x cardiac index (CI)
What is mean by cardiac index?
A measurement that related cardiac output to body surface area
What is the normal range of cardiac index?
2.4 - 4.2 L/min/m^2
How much oxygen, in ml, can one gram of haemoglobin carry?
1.34 ml
What is the calculation for Oxygen content of arterial blood (CaO2)?
CaO2 = 1.34 x [Hb] x % saturated Hb (SaO2)
What are some examples of conditions that can affect oxygen delivery to tissue?
Respiratory failure - Lowers pO2
Heart failure - Lowers CI
Anaemia - Lowers [Hb]
What causes the sigmoid shape of the oxygen dissociation graph?
The binding of 1 molecule of O2, increases the haemoglobin affinity to bind to other O2 molecules causing the steeper slope
The flat upper part of the sigmoid means that a moderate fall in pO2 will not affect oxygen loading
A steep lower part of the sigmoid means that only a small drop in pO2 is required for Hb to dissociate
What occurs as a result of Bohr shift to the right?
This means that O2 is released at higher pO2 levels, do it decreases the affinity of Hb for oxygen
What are some examples of factors that can cause a Bohr shift to the right?
pCO2
[H+]
Temperature
2,3-Biphosphoglycerate (A product of glycolysis which binds to haemoglobin and further decreases affinity)
What does a molecule of foetal haemoglobin contain?
2 alpha and 2 gamma subunits which interact less with 2,3-biphosphoglycerate
What are the advantages of foetal haemoglobin?
It interacts less with 2,3-biphosphoglycerate
This means it has a higher affinity for O2 compared to adult haemoglobin
This allows O2 to transfer from the mother to the foetus, even if the pO2 is low
Where is myoglobin found?
In cardiac and skeletal muscle
How many subunits does myoglobin contain?
1 haem group
What is the function of myoglobin and why?
Myoglobin releases O2 at very low pO2 and provides short term storage for O2 in anaerobic conditions
What does myoglobin in the blood suggest?
Muscle damage
What does the oxygen dissociation curve for myoglobin look like?
