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What is the % composition of air?
- 79% N2
- 21% O2
- <1% CO2, He, Ar, etc.
What is the pressure of air?
Pair = PN2 + PO2 = 600 mm Hg + 160 mm Hg = 760 mm Hg
What affects the solubility of gases in liquids?
- Partial pressure of the gas
- PPs of vaporized and dissolved gases will be equal at equilibrium
Is CO2 or O2 more soluble in water?
CO2 3.0 mmol/L vs. 0.155 mmol/L of O2 (at 100 mm Hg)
- 1. 160 mm Hg
- 2. 0.3 mm Hg
- 3. 100 mm Hg
- 4. 40 mm Hg
- 5. 40 mm Hg
- 6. 46 mm Hg
How does metabolism affect exchange?
Greater rate of metabolism = greater exchange
What is the blood in the pulmonary artery referred to as?
Mixed venous blood
What factors affect alveolar partial pressures?
- PO2 and PCO2 of inspired air
- Minute alveolar ventilation
- Rates at which respiring tissue use O2 and produce CO2
Most critical is rate of alveolar ventilation relative to rate of O2 use and CO2 production
What amount of O2 is transported in plasma? ... by hemoglobin?
- O2 not very soluble in plasma so only 3.0 mL/200 mL (1.5%) dissolved in plasma
- Other 197 mL transported by hemoglobin
What is Hb and Hb.O2?
- Hb = deoxyhemoglobin
- Hb.O2 = oxyhemoglobin
How many O2 molecules can hemoglobin bind?
What law does binding of O2 to hemoglobin follow?
- Law of Mass Action
- More O2 = more binds to hemoglobin (non linear, positive cooperativity)
How can you measure the amount of O2 bound to hemoglobin?
How many mL of O2 can one g of hemoglobin carry when 100% saturated?
what is the % hemoglobin saturation of arteriole blood and venous blood?
Arteriole blood = 98.5% saturated
Venous blood = 75% saturated
Name this graph and each of the points.
O2 Dissociation Curve
- 1. Systemic veins
- 2. Systemic arteries
- 3. % O2 unloaded by hemoglobin to tissues
How does affinity affect the O2 dissociation curve?
Increased affinity = more loading of O2 = less unloading = shift left
Decreased affinity = less loading of O2 = less unloading = shift right
How does temperature affect O2 saturation?
Higher temp = active tissues = more O2 unloading = more O2 delivery
How does pH affect O2 saturation?
Bohr effect - lower pH = increased O2 unloading
Active tissues produce more acid, pH decreases, shift right in saturation curve, more O2 unloaded
What is HbCO2?
How does CO2 affect saturation?
- HbCO2 has lower affinity for O2 than Hb
- Increased metabolic activity = increased CO2
- Increases O2 unloading in active tissue
What is 2,3-DPG?
Where and when is 2,3-DPG produced?
- In RBCs under conditions of low O2 such as anemia and high altitude
- Synth inhibited by oxyhemoglobin (Hb.O2)
What does 2,3-DPG do?
Decreases affinity of hemoglobin for O2, enhancing O2 unloading
How does CO affect saturation?
- Hemoglobin has greated affinity for CO than O2
- Prevents O2 from binding to hemoglobin
How is CO2 transported?
- 5-6% dissolved in plasma
- 5-8% bound to hemoglobin
- 86-90% converted to bicarbonate then dissolved in plasma
What is carbonic anhydrase?
Enz that converts CO2 and H2O to carbonic acid
What is the law of mass action in regards to CO2?
An increase in CO2 causes an increase in bicarbonate and hydrogen ions