21-4: Gas Exchange Flashcards
Dalton’s Law
the total pressure exerted by a mixture of gasses is the sum of the pressures exerted independently by each gas in the mixture
partial pressure
the pressure a gas exerts in a mixture of gases, determined by multiplying the percentage of the gas in the mixture by the total pressure of the mixture
What is the main gas in our atmosphere?
nitrogen (78.6%)
Oxygen makes up about __% of the atmosphere, and CO2 about __%.
21%, .04%
Why are certain gases moving into the body and not others?
partial pressure gradients promote gas movements in the body
PO2 in air
160
PCO2 in air
.3
PO2 in lungs
104
PCO2 in lungs
40
PO2 in tissues
<40
PCO2 in tissues
> 45
How is molecular oxygen carried in the blood?
dissolved in the plasma or bound to hemoglobin
What is the main way molecular oxygen is carried in the blood?
bound to hemoglobin - most (~98%) of O2 is bound to this carrier molecule
only ~2% is dissolved in the plasma since O2 is relatively insoluble in water
Each molecule of Hb can combine with __ molecules of oxygen. This binding process is ____.
4; rapid and reversible
oxyhemoglobin
hemoglobin carrying O2 (HbO2)
deoxyhemoglobin
hemoglobin that has released its O2 (HHb)
What determines whether O2 binds to or is released from hemoglobin?
partial pressure of oxygen (PO2)
oxygen-hemoglobin dissociation curve
graph depicting the relationship between PO2 and % sat of Hb
In the capillaries of the lungs, PO2 = __ and Hb is __% sat.
104; 98%
In tissues, where PO2 = __, Hb is __% sat.
40; 73%
Under resting conditions, __% of O2 bound to Hb is unloaded to tissues
25%
reserve supply
75% of O2 remains bound to Hb (venous reserve) for when oxygen demand increases
When PO2 drops below ___, ____ amounts of O2 are ____. What can cause this drop?
40; large; rapidly delivered to the tissues
vigerous muscle activity, exercise
If temperature __, pH ___, or PCO2 ___, O2 disassociates from Hb more readily.
temp increases; pH decreases; PCO2 increases
carbon monoxide poisoning
outcompetes O2 for a spot on Hb
carbon monoxide
colorless, odorless gas found in vehicle exhaust, burning wood or fossil fuels, cigarette smoke
What is the danger of CO?
it combines with Hb 200x faster than O2, preventing O2 from binding. This results in hypoxia
How is CO2 transported in the blood?
dissolved in plasma
bound to Hb
as bicarbonate ions
What is the main way CO2 is transported in the blood during internal respiration?
as bicarbonate ions (~70%)
~7% is carried in the blood plasma as a dissolved gas and ~23% is carried bound to Hb
carbaminohemoglobin
carbon dioxide bound to Hb
How is CO2 converted to a bicarbonate ion (HCO3-)?
CO2 enters RBCs, combines with H2O to form carbonic acid, which quickly disassociates into H+ and bicarbonate ions. Catalyzed by carbonic anhydrase
CO2 + H2O –> H2CO3 –> H+ + HCO3-
How is CO2 released during external respiration?
internal respiration events are reversed:
CO2 gas dissolved in plasma diffuses out of blood and into alveoli
CO2 bound to Hb splits due to pressure differences and diffuses into alveoli
Bicarbonate ion reaction is reversed, CO2 diffuses along its partial pressure gradient from teh pulmonary blood into the alveoli
Why does nitrogen have little effect in our bodies?
has low solubility at sea level and Hb doesn’t have a binding site
When is nitrogen a danger?
for deep sea divers, since N2 can dissolve inthe blood as atmospheric pressure goes up - if a diver comes up too fast, N2 gas bubbles out of his blood causing the bends, nausea, and seizures
