Respiration Lecture 09: Transport of Gas by the Blood Flashcards
Fx of hemoglobin
Binds O2 from alveolus and delivers to tissue. Normally at 1.39 ml O2/g Hb. Comes by alveolus in venous blood, leaves to tissues in arterial blood
2 methods for transporting O2 in the blood
1) dissolved in fluid phase of blood
2) O2 bound by Hb
What produces Hb?
RBC as it’s forming
How to calculate dissolved oxygen content
oxygen content = oxygen solubility X arterial partial pressure of O2 (PaO2)
cO2 =
How does increased H+ affect O2 ability to bind Hb?
Decreased binding
Normal Hb bound O2 content
1.39 ml O2/gm Hb or 20.85 ml O2/dL blood
What comprises “globin” region of Hb?
imidazole group
Percent saturation of O2 =
ratio of O2 bound Hb to the total Hb binding capacity times 100
(HbO2 bound/HbO2 capacity)*100
greater PO2 –> binding ability of O2 on Hb
Increases. Oxygen saturation is an indicator of PO2
P50
partial pressure of O2 that can bind 50% of Hb (a measure of the affinity of Hb for O2)
ability of Hb to bind O2 is fx of 3 things:
H+, CO2, and temp
increased temp –> Hb affinity for O2?
Decreased
increased PCO2 –> Hb affinity for O2?
Decreased
Where is Hb’s affinity for O2 highest?
lungs
Where is Hb’s affinity for O2 lowest?
tissues (muscles)
Where is affinity for protein-bound CO2 lowest?
lungs
Fastest way to get rid of CO2 at the lung
dissolving CO2
Total blood oxygen content =
Hb Bound O2 + Dissolved O2
=(1.39 * Hb * %sat) + (0.003 * PO2)
Hb will = 15 unless told otherwise
Do For BOTH arterial and venous blood and add together to get total content
Volume of O2 extracted by the tissues =
arterial content of O2 (CaO2) - venous content of O2 (CvO2) (oxygen extraction driven by mitochondria)
carbamino compounds fx
proteins that bind CO2
3 ways to transport CO2
1) dissolved
2) protein bound
3) bicarbonate
2 ways to transport O2
1) dissolved
2) protein bound
What state must gas be in to enter alveolus?
Dissolved state
carbonic anhydrase equation
CO2 + H2O H2CO3 HCO3- + H+
How does CO2 get from tissue to alveolus?
CO2 leaves tissue, dissolved and enters RBC where it is converted to HCO3- by carbonic anydrase and released again. Near alvelus, HCO3- enters RBC, transformed back into dissolved CO2 and transferred to alveolus.
Why is oxygen binding curve sigmoid?
Hard to bind sites 1 and 4 on Hb, easy to bind sites 2 and 3
How many O2 molecules can 1 Hb bind?
4 (1 on each heme group)
What should partial pressure of alveolar air equal?
partial pressue of disssolved O2
What 2 things determine volume of O2 dissolved in the blood?
partial pressure of O2, temperature
Acidosis
decrease in blood pH from normal range of 7.35-7.45
Increased PCO2 –> O2 release to tissues?
increased
decrease in blood PCO2 –> loading of O2 in alveoli?
increased
increased 2,3-DPG –> Hb affinity for O2
decrease
Where is 2,3-DPG produced?
muscles
Normal Hb saturation
97%
Normal arterial PCO2
40mmHg
Haldane Effect
the formation of carbamino compounds weakens the Hb affinity for O2 in the tissue and aids in unloading of O2. In the lung, PO2 antagonizes the carbamino formation and aids the unloading of CO2. Facilitates CO2 off loading and produces a physiological dissociation curve that is steeper than for the arterial or venous curves alone
Major form of CO2 storage in the blood
HCO3
Importance of HCO3- in the blood
acts as pH buffer in blood
Why will cessation of ventilation have a greater effect on O2 than CO2?
body has stores of HCO3- outside the blood
