Unit 3 - Transport of oxygen and carbon dioxide Flashcards
How many oxygen molecules is one haem group capable of binding to?
One Oxygen molecule
How many haem groups does one haemoglobin molecule contain?
4
Give the equation for haemoglobin binding to Oxygen
Hb + 4O2 ⇌ HbO8
What is formed when haemoglobin binds to oxygen?
Oxyhaemoglobin
How does Oxygen get from the alveoli into the blood?
Diffuses from alveoli into blood capillaries down a concentration gradient
What occurs to the Hb once the first molecule of O2 has been taken up by it?
The Hb changes shape
Why does Hb change shape once the first molecule of O2 has been taken up?
- enables Hb to take up the 2nd O2 more quickly
- the 3rd O2 quicker still
- 4th O2 even more quickly
- allows a concentration gradient to be maintained as no free oxygen is dissolved into the blood
What is positive cooperactivity?
- Hb which changes shape once 1st molecule of O2 is taken up
- enables 2nd, 3rd, 4th O2 molecules to be taken up more quickly
Where is oxyhaemoglobin transported to?
Respiring tissues
When oxyhaemoglobin is transported to respiring tissues what happens?
It releases O2 molecules
What is the determining factor for whether O2 is picked up or released?
The partial pressure of O2 (pO2)
What is an oxygen dissociation curve?
a way of showing how the binding of O2 varies at different pO2
Is the pO2 greater in the lungs than in the capillaries of respiring issues?
Yes
What is the shape of the oxygen dissociation curve?
An ‘S’ shape
What does the ‘S’ shape of the oxygen dissociation curve mean for change in pO2?
For a relatively small change in pO2 there is a large change in the % of Hb saturated with O2
What is the x axis for an oxygen dissociation curve?
p(O2) (kPa)
What is the y axis for an oxygen dissociation curve?
% Hb saturated with O2
Why can the oxygen saturation of the blood never be 100%?
Some Hb will be bound to CO2
What is the effect of a drop of oxygen levels on Hb?
Causes O2 to be released from Hb
Under what physiological conditions is Hb able to release even more O2?
- CO2 concentrations increase
- Temperature increases
- Blood pH increases
How is Hb able to release more O2 under certain conditions?
The oxygen dissociation curve shifts to the right
What is Bohr shift?
The movement of the oxygen dissociation curve to the right
Organisms that live in an environment of relatively low pO2 have Hb that differs to organisms which live in a normal environment how?
The Hb has a higher affinity for O2
What is the effect of Hb with a higher affinity for O2 on the oxygen dissociation curve?
Shifts the curve to the left
Give an example of an organism that has Hb with a higher affinity
A foetus
Where does a foetus obtain its Oxygen from?
Maternal Haemoglobin
What is an advantage of respiring cells producing large amounts of CO2?
- the oxygen curve is shifted to the right
- so more oxygen can be released from the haemoglobin
Why does foetal haemoglobin have a higher affinity for O2?
- a foetus obtains its O2 from maternal haemoglobin
- in the placenta maternal Hb releases the O2 which diffuses into the foetal bloodstream
- at the pO2 at which maternal Hb releases O2 which diffuses into the foetal bloodstream
- pO2 at which maternal Hb releases O2 the foetal Hb is able to pick up
- Foetal Hb becomes 95% saturated
What % of CO2 is transported in blood plasma?
5%
What are the 3 ways transport of CO2 occurs?
- in blood plasma
- attaches to amine group of haemoglobin
- transported as hydrogen carbonate in red blood cells
How is CO2 transported in blood plasma?
- CO2 dissolves into blood plasma to form carbonic acid
- the acid dissolves to give Hydrogen carbonate (HCO3-) ions and protons
What is the function of plasma proteins in the blood in regards to CO2 transportation?
- plasma proteins buffer the protons
- and so protect the pH from decreasing and denaturing proteins in the blood
What is the equation for CO2 transport in blood plasma?
CO2 + H2O ⇌ H2CO3 ⇌ H+ + HCO3-
What % of CO2 is transported by attaching to the amine group of haemoglobin?
10
What % of CO2 is transported in red blood cells as hydrogen carbonate?
85
How is CO2 transported in red blood cells?
- CO2 diffuses into red blood cells
- Enzyme carbonic anhydrase catalyses the reaction of CO2 and water to produce carbonic acid which dissociates into HCO3- ions and H+
- HCO3- diffuse into plasma
- H+ buffered by Hb to form Haemoglobic acid, triggering the release of 4 molecules of O2
What is chloride shift?
- due to HCO3- ions diffusing out of the cell down a concentration gradient charge becomes imbalanced
- to maintain electrical charge there is an inward diffusion of chloride ions
What happens to the processes of CO2 transportation when the lungs are reached?
All processes are reversed
Why is carbonic anhydrase used to catalyse the reaction of CO2 and water within red blood cells?
- so the reaction occurs quickly
- maintains the concentration gradient of CO2
What is the relative position of the foetal haemoglobin curve relative to the adult haemoglobin curve?
The foetal curve is to the left of the adult haemoglobin
Why is the foetal haemoglobin curve to the left of the adult haemoglobin curve?
- placenta has low pO2
- adult Hb will release O2
- foetal Hb is still able to take up some O2 in placenta
- foetal Hb has a higher affinity for O2 than adult Hb
