respiration - lecture 4 Flashcards
describe transport of o2
amount of gas dissolved in liquid is proportional to its partial pressure - henrys law increase partial pressure in air = more diffuses into fluid
proportional to pressure gradient
describe o2 physically dissolved in plasma
o2 is relatively insoluble in h2o
amount of o2 dissolved in blood = v small
linearly proportional to po2
ex = in 100ml plasma, 0.3ml of o2 at a po2 of 100mmhg - that will dissolve
if o2 were only found in plasma what would happen
the tissue demand for o2 would never be met
o2 consumption (VO2) by body cells = 300ml o2/min
describe Hb
found in rbcs
permits whole blood to take up 65 times as much o2 as plasma at po2 100mmhg
what does each molecule of Hb have
4 subunits bound together
each made up of heme joined to a globin
heme contains fe++ ion that can bind to one molecule o2
= 4 oxygens per hb
what is Hb essential for
transport of o2 by blood since combines rapidly and reversibly with o2
Hb + O2 <–> HbO2
give ex of how Hb helps
at po2 100mmhg
total amount o2 dissolved in blood = 0.3vol. %
total amount of O2 bound to Hb = 19.5 vol.% (65x more)
the total amount of o2 in arterial blood = 20vol%
does o2 bound to hb contribute to po2 of blood, explains
NOOO
(like new compound, not in plasma anymore)
only molecules dissolved in blood plasma contribute to po2
the po2 of the plasma does determine amount of o2 that combines with Hb = higher po2 in plasma = more o2 binds Hb
describe HbO2 dissociation curve
determines amount of O2 carried by Hb for any given partial pressure
curve flat at high values po2 and steep at low values po2
sigmoidal shape
what does Hb provide
automatic mechanism that matches tissues o2 supply to tissue need
describe at low values of po2 - o2 dissociation curve
as seen in peripheral tissues
small drop in po2 unloads the o2 from the hb to the tissue
give ex of drop in po2 - o2 dissociation curve
drop in po2 from 40–>20mmhg results in decrease in %HbO2 from 75–>35%
drop in po2 from 100–>80mmhg results in decrease of less than 3%
describe po2 - o2 dissociation curve graph
40–>20, 75% so gives up o2 so tissue can use it
at steep portion = decrease Hb sat at 38%, desat so lets O2 go to exercising muscles
100–>80, at alveolar level want to saturate so can transfer to peripheral, desat not by much even tho still 20mmhg increase
describe climbing mount everest
barometric pressure is less than at sea level bc at high altitude
less pressure of air on shoulders
might be 80 still want to sat hB - do not want to desat = tissues need it
describe o2 dissociation curve o2 - total
total 02 = sum of o2 dissolved and combined with Hb
even at po2 600 - dissolved o2 = o2 dissolved in plasma is v small
describe pathway of o2
alveolar level - diffuses down pressure gradient - dissolved o2 then binds to hb - in pulmonary cap
goes to heart
o2 moves down pressure gradient and moves out of rbc and diffuses out towards cells
describe shape of hemoglobin dissociation curve
the quaternary structure of hb determines affinity for o2
combination of first heme of hb with o2 increases affinity of second heme for o2, etc. = cooperative binding
conformational change as o2 binds hb
describe shape of myoglobin dissociation curve
hyperbolic shape
desat only at very low partial pressures
safety mechanism = still have reserve of o2 at skeletal muscle level
describe myoglobin
found in skeletal muscle
binds only one o2 molecule
o2 myoglobin curve = hyperbolic shape
follows that myoglobin will release its o2 only at v low po2
what does total amount of o2 in blood mostly depend on
hb concentration
describe under anemia conditions - o2 dissociation curve
conditions of decreased h. concentration - even when o2 sat is 97.5%, less o2 can be carried in blood by hb
total o2 content less
what is bohr effect
shift in o2 dissociation curve to right when blood co2 and/or temp increases or blood pH decreases
factors have little effect on total amount of o2 combined with hb above 80mmhg
describe bohr effect graph
hb desat at 50% - starts unloading earlier = now available for tissues
knows you are exercising = now need o2 available asap
describe example of bohr effect
when exercise = increase co2 and acid production and generate heat
curve shifts to right means that for given drop in po2 = additional amount of o2 is released from hb to working tissues
what is opposite of bohr effect
reverse conditions = lower pco2, lower temp and increase ph
describe carbon monoxide poisoning
CO has extremely high affinity for o2 binding sites in hemoglobin = 210-fold
reduces amount of o2 bound to hemoglobin = problem since need o2 to be carried by hb
shifts o2 hb curve to left and decreases unloading of o2 to tissue * structure, binds co before o2 but also holds on more for the few o2 molecules it binds
describe what happens in CO poisoning
there is little stimulation to increase ventilation bc pao2 remains normal
in arterial blood
po2 in blood = due to dissolved amount, stays constant, brain senses this and not O2 bound to hb
describe transport of co2
primary product of oxidative processes taking place in body cells
removed from tissues by the blood
name the 3 ways co2 is carried in blood
physically dissolved in blood
combined with hb to form hbco2
as bicarbonate
describe physically dissolved in blood - transport of co2
10%
carried as co2
physically dissolved
describe combined with hb to form hbco2 - transport of co2
11%
combines with globin portion not heme
so no competition on hb
describe as bicarbonate - transport of co2
79%
co2 combines with h20 to produce carbonic acid (h2co3)
reaction is aided in rbcs by carbonic anhydrase
co2 + h2o –> (with help of carbonic anhydrase) h2co3
h2co3 then ionizes into bicarb (hco3-) and H+ ions as
h2co3 –> hco3- + h+
describe transport of co2 through tissue capillaries
10% dissolved co2 in plasma
diffuses into rbc and binds hb (11%)
rest = combine with water
hco3- diffuses out and transported in blood plasma, membrane is permeable
cl- moves into cell - to keep neutrality
describe reactions of transport of co2
all reversible
can proceed in either direction
depends on conditions like pco2
what happens if co2 production increases
production of hbco2, hco3- and h+ increases
in peripheral tissues
but opposite happens at lung capillaries - equations move in opp dirs
what happens when you lower blood pco2
results in hco3 - going to h2co3 and further into co2 and h2o and hbco2 generating hb and co2
situation occurs when venous blood flows through lung capillaries
h+ +hco3- (carbonic anhydrase) –> h2co3 –> h20 + co2
hbco2 –> hb + co2
describe diffusion of co2 through pulmonary capillaries
bc blood pco2 higher than alv pco2 = net diffusion from blood into alveoli lowers blood pco2
normally = as fast as co2 is generated from hco3- and hbco2 - it diffuses into alveoli
co2 moves into plasma and to alveoli
bicarb moves back into cell
describe transport of co2 pathway
tissue capillary - dissolved co2 moves into plasma and cap down concentration gradient and then is transported in the 3 ways
all goes in reverse to expire co2
describe graph of co2 content
co2 content = almost linear
not sigmoidal
what is haldane effect
in tissue capillaries hb free of o2 may combine with h+ (h+ + hb02 <–> HHb + o2)
occurs bc reduced hb (deoxyhb) is less acidic than hbo2
hb acts as buffer - iron in hb -= 2+ or 3+ –> accepts nitrogen ions
describe haldane effect
reduced hb in tissue cap helps with blood loading of co2 by pushing eq 1 and 2 to right = haldane effect
1 = co2 + h20 –> h2co3
h2co3 then ionized into bicarb and h+ ions with help of carbonic anhydrase
2 = h2co3 –> hco3- + h+
(moves towards right)
le chateliers principle - anything that stabilizes proton produced will cause reaction to shift to right
for a given pco2, the more co2 is carried in deoxygenated blood than in oxygenated blood
describe haldane effect graph
carry more co2 when desat
carry more cos when blood deoxygenated = good since wanna pick up o2
o2 saturation of blood influences co2 dissociation curve by shifting to right
haldane effect = fact that mixed venous blood can carry more co2 than can arterial blood
describe co2 dissociation curve
co2 dissociation curve has not steep or flat portions
relationship between co2 content and pco2 = almost linear
whats happens if hyperventilate - co2 transport
bring more fresh air and breathe out more = alveolar pco2 decreases so co2 content in blood decreases but not same for o2 content since curve plateaus
increase po2 just a bit but o2 blood still saturated = wont increase po2 much
whats happens if hypoventilate - co2 transport
means that if we hypoventilate and alveolar pco2 rises then arterial capillary and venous co2 also rise
what does doubling alveolar ventilation do
doubling alveolar ventilation halves alveolar pco2 = follows that increase in alveolar ventilation proportionally increases co2 removal
