o2 gas transport Flashcards
when a gas diffuses into the blood, what is the first thing that happens?
it first dissolves in the plasma
why are gas transport mechanisms needed?
bc o2 and co2 are less soluble in plasma than in air
do these other mechanisms contribute to the partial pressure of the gas in the blood?
no
most o2 that dissolves in plasma is rapidly taken up by what? what is this movement driven by?
red blood cells; partial pressure gradient bw the plasma and ISF.
some o2 remains in the ISF but the other 98% binds to what?
hemoglobin (Hb)
what does hemoglobin do?
increases the oxygen content of the blood by 50-fold
what is oxygen content?
the total o2 present per unit volume
each hemoglobin consists of what? what are they called and how many are there?
4 protein subunits; 2 alpha-globin; 2 beta-globin
each subunit is bound to what?
heme
contains an iron atom that can reversibly bind to one oxygen molecule? this means that each hemoglobin can do what?
heme; bind up to 4 molecules of oxygen
binding of o2 to hemoglobin displays what? what does that mean?
cooperativity; as binding sites are occupied by O2, the affinity of the remaining sites will increase
a site bound to o2 is said to be _________, and is referred to as _____________.
oxygenated; oxyhemoglobin
a site not bound to o2 is said to be _________, and is referred to as _____________.
deoxygenated; deoxyhemoglobin
the percentage of o2 binding sites that are oxyhemoglobin depends on what?
the partial pressure of O2 in the blood
what is used to visualize the relationship bw Po2 and the oxyhemoglobin percentage?
oxygen-dissociation curve
the proportion of binding sites occupied by o2
saturation
the percentage of oxygenated binding sites at any given partial pressure
percent saturation
what is the percent saturation in the pulmonary veins and systemic arteries? (Po2 = 100mmHg here)
close to 100%
what is the percent saturation in the pulmonary arteries and systemic veins? (Po2 = 40mmHg here)
75%
the affinity of Hb of O2 _____________ as blood moves thru the pulmonary capillaries, and __________ as blood moves thru the systemic capillaries
increases, decreases
increased affinity promotes what? what does that mean?
loading; binding of O2 to Hb
decreased affinity promotes what? what does that mean?
unloading; unbinding of O2 from Hb
what does a leftward shift in the dissociation curve indicate?
increased affinity that promotes loading
what does a rightward shift in the dissociation curve indicate?
decreased affinity that promotes unloading
what are factors that affect affinity?
Pco2, pH, temp, 2,3-DPG levels
which factors will decrease Hb affinity for O2 and shift the oxygen-dissociation curve to the right? (promoting unloading) where would these conditions be favorable?
increased Pco2, temp, and 2,3-DPG lvls; decreased pH; systemic capillaries where unloading delivers O2 to tissues
which factors will increase Hb affinity for O2 and shift the oxygen-dissociation curve to the left? (promoting loading) where would these conditions be favorable?
decreased Pco2, temp, and 2,3-DPG lvls; increased pH; pulmonary capillaries, where loading brings o2 into the blood
why does pco2 have a direct effect on O2 affinity? what happens when this occurs?
bc co2 also binds to hemoglobin, when it does it produces a conformational change in Hb that decreases Hb affinity to O2.
what happens when Pco2 increases in the systemic capillaries, as co2 moves from ISF to plasma, to red blood cells where it binds to Hb?
decreases Hb affinity to O2, promoting unloading
what happens when Pco2 decreases in the pulmonary capillaries, as co2 moves from plasma to alveolar air?
causes co2 to detach from Hb, increasing its affinity of O2, promoting loading
how does Pco2 indirectly affect Hb affinity?
by affecting blood pH
what does increased Pco2 do to pH?
increase H+ conc, decreasing pH
H+ binding causes to Hb causes what?
a conformational change that decreases that affinity of Hb for O2
the interaction of Pco2 and pH on the affinity of Hb for O2 is called
the Bohr effect
what does increased temp and metabolic activity do?
decreases affinity and increases unloading
is produced in red blood cells as a consequence of glycolysis
2,3-DPG
what happens when 2,3-DPG binds to Hb?
decrease affinity of Hb for O2 and promote unloading
2,3-DPG binds only to deoxyhemoglobin (t or f)
true
normally 2,3-DPG has a small effect on Hb affinity but under what conditions does its effect increase?
under low o2 conditions like high altitudes
