Transport of oxygen Flashcards
What are the forms in which oxygen can be transported?
Form 1: Oxygen in physical solution (2%)
Form 2: Oxygen in chemical form (98%)
How is oxygen transported in a physical solution?
Form 1
Free oxygen is dissolved in blood
Volume and partial pressure of oxygen dissolved in blood
Form 1
V = 0.3ml/100ml, PO2 = 100mmHg in arterial blood
V = 0.13ml/100ml, PO2 = 40mmHg in venous blood
What does O2 tension determine?
Form 1
Rate and direction of O2 diffusion
% of hemoglobin saturation
How is oxygen transported in the chemical form?
Form 2
Combines with Fe2+ of hemoglobin forming HbO2, HbO4, HbO6 and HbO8
What does O2 in the chemical form determine?
The O2 capacity and O2 content
What is O2 capacity?
Volume of O2 in ml present in chemical combination with Hb in 100ml blood when Hb is fully saturated
How much oxygen can each gram of Hb carry?
1.36 ml of O2
What is the general O2 capacity?
O2 capacity = 1.36 x Hb content
= 1.36 x 15g%
=20ml/100ml blood
What is O2 content?
Volume of O2 in ml present in chemical combination with Hb in 100ml blood
Not fully saturated
O2 content in arterial blood
At PO2 = 100mmHg → O2 content = 19ml/100ml blood
O2 content in venous blood
At PO2 = 40mmHg → O2 content = 14ml/100ml blood
How is %O2 saturation of Hb calculated?
(O2 content/O2 capacity) x 100
%O2 saturation in arterial blood
(19/20) x 100 = 95% or more
%O2 saturation in venous blood
(14/20) x 100 = 70%
What does the oxygen-hemoglobin dissociation curve represent?
It represents the relationship between partial pressure of O2 (blood PO2) and % Hb saturation (SaO2)
Describe the oxygen-hemoglobin dissociation curve
Sigmoid
What does the shape of the oxygen-hemoglobin dissociation curve represent?
Saturation of Hb with oxygen varies with partial pressure of oxygen
What does the plateau phase of oxygen-hemoglobin dissociation curve represent?
At high partial pressure of oxygen, such as in the lung tissue, oxygen taken up by Hb
Uptake of one O2 facilitates the uptake of further O2
What does the sloped phase of the oxygen-hemoglobin dissociation curve represent?
At low partial pressures of oxygen, such as in the tissues of the body, oxygen released to the tissue
Low affinity of Hb to O2
What causes the sigmoid shaped oxygen-hemoglobin dissociation curve?
Presence of 4 heme groups in the Hb
Each group can combine to one molecule of O2 and the groups differs in their affinity to O2 as the O2 tension increases
What factors cause a rightward shift in the oxygen-hemoglobin dissociation curve?
Increased blood PCO2 (Bohr effect)
Increased concentration of 2,3 DPG
Increased body temperature
Increased blood H+ concentration (decreased blood pH, acidosis)
There is decreased affinity of Hb to O2 leading to increase O2 release to the tissues
What factors cause a leftward shift in the oxygen-hemoglobin dissociation curve?
Decreased blood PCO2
Decreased concentration of 2,3 DPG
Decreased body temperature
Decreased blood H+ concentration (increased blood pH, alkalosis)
Hemoglobin F (Fetal Hb)
There is increased affinity of Hb to O2 leading to decrease O2 release to the tissues
What is myoglobin?
Iron containing pigment present in skeletal muscle
Purpose of myoglobin
Stores O2 in the muscles
How many oxygen molecules can each myoglobin bind?
One molecule
Describe the shape of the myoglobin dissociation curve
Rectangular hyperbola
At what partial pressure is myoglobin saturated?
At tissue level, PO2 = 40mmHg, myoglobin is fully saturated
During muscular exercise, if PO2 < 40mmHg, myoglobin release O2 to the muscles
