Oxygen Transport

Nota:

• Average: Oxygen: 100mmhg Carbon dioxide: 40mmHg Water Vapour: 47mmHg Nitrogen: 573mmHg

Nota:

• Blood composition changes as it passes thru the lungs, gas exchange at the alveoli. Blood coming from Pulmonary Artery: Oxygen: 40mmHg Carbon Dioxide: 47mmHg Blood coming from lungs into pulmonary vein: Oxygen: 100mmHg Carbon Dioxide: 40 mmHg Arterial blood:Blood from pulmonary arteries with bronchial veins and left ventricle.Oxygen: 95mmHgCarbon Dioxide: 40 mmHg

Nota:

• Dissolved and carried in blood in 2 forms: Dissolved Combined with haemoglobin

1. Haemoglobin

   Nota:

   • 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+.
   1. Quarternary Structure

      Nota:

      • 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.

Nota:

• 3 terms to remember: Oxygen Capacity: Amt of o2 which can combined with Hb. at normal its 15g/100ml. Oxygen Saturation: Percentage of available binding sites for Hb to attach. Saturation Formula: O2 with Hb/O capacity X 100 Oxygen Content: Amt of molecular oxygen that is released after destroying binding power of Hb.

1. Equation to determine O2 content

   Nota:

   • (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

Nota:

• 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) notable points 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.

1. Bohr Effect

   Nota:

   • 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.
2. 2,3 DPC

   Nota:

   • Produced by glycolysis of RBC binds to deoxyHB therefore decrease affinity of oxygen binding.

Nota:

• Different type, oxygen storage in muscle.  Binds to one oxygen

Nota:

• CO has higher affinity to Hb. Forms carboxylhaemoglobin. Symptoms of patient will be hypoxic. But no cyanosis. COHb will be cherry red in color.