Blood composition changes as it passes thru the lungs, gas exchange at the alveoli.
Blood coming from Pulmonary Artery:
Carbon Dioxide: 47mmHg
Blood coming from lungs into pulmonary vein:
Carbon Dioxide: 40 mmHg
Arterial blood:Blood from pulmonary arteries with bronchial veins and left ventricle.Oxygen: 95mmHgCarbon Dioxide: 40 mmHg
3 Blood Oxygen Transport
Dissolved and carried in blood in 2 forms:
Combined with haemoglobin
Molecular weight of 64450KDs, 4 subunits which also consists of a haem molecule connected in a polypeptide chain.
2 alpha chains (141aa) and 2 beta chains (146 aa)
The haem molecule consists of a porphyrin derivatiive and one atom of Ferrous Fe2+.
3.1.1 Quarternary Structure
Quarterany structure aids in loading of the oxygen molecules.
Available in 2 states
Tense and Relaxed.
It is also allosteric.
I.e when one molecule binds, it enables the other molecules to bind to them easier.
4 Oxygen capacity, saturation and content
3 terms to remember:
Amt of o2 which can combined with Hb. at normal its 15g/100ml.
Percentage of available binding sites for Hb to attach.
Saturation Formula: O2 with Hb/O capacity X 100
Amt of molecular oxygen that is released after destroying binding power of Hb.
4.1 Equation to determine O2 content
(1.34 X Hb X Sat/100)+ 0.003 X Partial Pressure Oxygen
Saturation is 97.5% for normal Hb
1.34 is constant for Hb
0.003 is the solution constant for Oxygen
5 Hb-O2 equilibrium curve
Important factors that shift the curve to the right.
increase in H conc i.e pH decreases
Increases in temperature
Increases in carbon dioxide conc
increase in 2,3 diphosphoglycerate (2,3 DPG)
Partial pressure of oxygen vs % Saturation
0 vs 0
20 vs 35
27 vs 50
40 vs 75
100 vs 97.5
Flat upper portion shows the o2 loading of the lungs
The steep lower portion shows the o2 diffusion into the tissues.
5.1 Bohr Effect
Shift the OEC due to the change in blood pH and Co2.
hydrogen ions bind to the histidine residues on Hb and hence initiates conformational changes and it decreases affinity towards oxygen
This leads to enhanced oxygenation of blood in the lungs and release of oxygen in tissues.
5.2 2,3 DPC
Produced by glycolysis of RBC
binds to deoxyHB therefore decrease affinity of oxygen binding.
6 Haemoglobin vs Myoglobin
Different type, oxygen storage in muscle.
Binds to one oxygen
7 CO poisoning
CO has higher affinity to Hb.
Symptoms of patient will be hypoxic. But no cyanosis.
COHb will be cherry red in color.