Carriage of O2 and CO2 in the blood Flashcards
What are the two forms that oxygen is carried?
1) Dissolved in blood
2) Combined with haemoglobin
What is the equation for partial pressure?
Partial pressure = fractional concentration X pressure
What is the amount of gas in a solution proportional to?
Temperature
What is the equation of oxygen saturation?
HbO2 /
(HHb + HbO2)
/ means divided
Hb02 = oxyhaemoglobin
HHb - deoxy hb
What is the equation for volume of o2
Volume of O2 = SO2 X [Hb] X 1.39
S02 = oxygen saturation Hb = Hb concentration 1.39 = Huffners constant (Hufner worked out what the molecular weight of Hb was and how much moles of O2 haemoglobin should carry.
What is the primary structure of Hb?
141-146 amino acids per chain
What is the secondary structure of Hb?
Globular structure
What is the tertiary structure of Hb?
“Crevice” for haem and o2 binding
What is the quaternary structure of Hb?
4 chains (2 ALPHA & 2 BETA)
Haemoglobin
Each chain has haem group
Each haem group has iron in the middle
Each iron binds an oxygen
What happens in R form of haemoglobin?
R means Relaxed form.
The chains relax when o2 binds so gap opens.
High affinity
What happens in T form?
T means Tensed.
Bonds in chain are very tightly squashed so o2 cant get in so low affinity.
What if hufner constant?
Each gram of Hb should carry 1.39 mils of gaseous 02.
What is the oxygen sats in arterial blood?
Nearly 100
What does the haemoglobin-oxygen dissociation curve show?
The oxygen dissociation curve is a graph that shows the percent saturation of haemoglobin at various partial pressures of oxygen.
Why is it sigmoid shaped?
The binding of the first molecule is difficult. However, this facilitates the binding of the second, third and fourth, this is due to the induced conformational change in the structure of the haemoglobin molecule induced by the binding of an oxygen molecule.
What can affect this curve?
Temperature
PH change
High 2,3, DPG
What happens in high temperature
Curve displaced to the right - makes it give up more 02 to tissues
What happens in low PH?
Curve shifts to the right (acidic). A decrease in pH shifts the standard curve to the right, while an increase shifts it to the left. This is known as the Bohr effect.
What happens in high 2,3 DPG?
Curve shifts to the right.
What is thalassaemia?
Absent globin chain
What is sickle cell anaemia?
Defective globin chain
What is a buffer?
Solution that can minimise changes in the free H+ concentration and therefore in PH.
what does a buffer consist of?
A weak acid and its base
Whats in our blood buffer system?
Bicarbonate, plasma proteins, hb and phosphate
What two forms is CO2 carried in?
1) dissolved in the blood
2) carbamino compounds (bound to amino group on proteins)
