O2 and CO2 Transport Flashcards
Diffusion of gas into a tissue is directly proportional to (3):
ADP
- surface area (A)
- Diffusion coefficient (D)
- Partial pressure difference (P1-P2)
Diffusion of gas into a tissue is inversely proportional (1):
to the thickness of the diffusion barrier (T).
RBCs spend about ___ seconds in pulmonary capillaries next to alveoli.
0.75 seconds
At rest, RBCs/Hb become fully saturated about after about how much time in the pulmonary capillary next to the alveolous?
- 0.25 seconds.
- 1/3rd way through pulmonary capillary.
During times of increased CO, RBCs/Hb become fully saturated about after about how much time in the pulmonary capillary next to the alveolous?
- 0.25 seconds.
- 1/2 way through pulmonary capillary.
- RATE OF BLOOD FLOW FASTER.
Cause of hypoxia on exertion:
- increased CO = increased rate of blood flow.
- if barrier of diffusion is thickened (fibrosis), there is not enough time for RBCs to reoxygenate when passing through pulmonary capillaries.
Fick’s Law governs the diffusion of gas at the level of the alveoli. What is the equation (to determine what increases and decreases diffusivity)?
V = AD(P1-P2)/T
Perfusion limited:
- Equilibrium (PA-Pa equalize) is reached within the amount of time the blood is in the pulmonary capillary.
Diffusion limited:
- Equilibrium (PA-Pa equalize) DOES NOT OCCUR within the time the blood is in the pulmonary capillary.
Hemoglobin general structure:
- heme component (iron): binds O2.
- Two alpha chains, two beta chains.
Each gram of hemoglobin is capable of combining with about 1.39mL of oxygen under optimal conditions, but only 1.34 mL in blood. Why?
- Hemoglobin in blood exists in different forms; such as methemoglobin.
At a PO2 of 100mm Hg (arterial blood), hemoglobin is what percent saturated?
- about 97.4% (not 100% due to methemoglobin, etc.)
- All 4 heme groups bound to O2.
At a PO2 of 40mm Hg (venous blood), hemoglobin is what percent saturated?
- 75%
- 3/4 heme groups bound to O2.
What does a shift in the Hb binding curve to the right indicate?
- decreased Hb affinity for O2
- more O2 unloading
What shifts the Hb binding curve to the right (decreased Hb affinity for O2/more unloading)?
- increased PCO2 (decreased pH)
- increased 2,3-BPG
- increased temperature
What does a shift in the Hb binding curve to the left indicate?
- increased Hb affinity for O2
- less O2 unloading
What shifts the Hb binding curve to the left (increased Hb affinity for O2/less unloading)?
- decreased PCO2 (increased pH)
- decreased 2,3-BPG
- decreased temperature
PCO2, pH, and temperature levels in metabolically active tissues:
- higher PCO2
- lower pH
- higher temperature
FACILITATES O2 UNLOADING FROM Hb
Anemia effect on oxygen in blood:
- lack of RBCs.
- Less RBCs = less Hb.
- CaO2 decreases.
Carbon monoxide effect on oxygen in blood:
- less O2 bound to Hb.
- decreased SaO2 and CaO2.
CO2 is produced in the tissues and then carried to the lungs in the venous blood in three forms:
- dissolved CO2 (5-10%)
- carbaminohemoglobin (5-10%; CO2 bound to Hb)
- HCO3- (90%)
Steps in the process of CO2 transport as HCO3- in blood (formation to expiration):
- CO2 produced in tissue; diffuses into RBC.
- CO2 + H2O → H2CO3 → H+ + HCO3- (CA catalyzed)
- HCO3- leaves RBCs for Cl- (chloride shift)
- H+ in RBCs binds to deoxyHb.
- In lungs, all above reactions occur in reverse.
Steps in the process of HCO3- to CO2 at lungs:
- HCO3- enters RBCs in exchange for Cl-.
- HCO3- + H+ → H2CO3 → CO2 + H2O.
- CO2 expired.
Haldane effect:
- deoxygenated blood increases Hb ability to carry CO2.
- CO2 loading in tissue.
- oxygenated blood decreases Hb ability to carry CO2.
- CO2 unloading in lungs.
Bohr effect:
- H+ formed by the dissociation of carbonic acid into H+ and bicarbonate binds to amino acid residues on the globin chains of Hb.
- Hb conformation change; oxygen released into tissues.
increased H+ levels in the tissue (decreased pH) leads to increased oxygen unloading.
What form of hemoglobin buffers hydrogen ions formed by the dissociation of carbonic acid?
deoxyhemoglobin
