respiration - lecture 4

Question 1

describe transport of o2

Answer 1

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

Question 2

describe o2 physically dissolved in plasma

Answer 2

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

Question 3

if o2 were only found in plasma what would happen

Answer 3

the tissue demand for o2 would never be met
o2 consumption (VO2) by body cells = 300ml o2/min

Question 4

describe Hb

Answer 4

found in rbcs
permits whole blood to take up 65 times as much o2 as plasma at po2 100mmhg

Question 5

what does each molecule of Hb have

Answer 5

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

Question 6

what is Hb essential for

Answer 6

transport of o2 by blood since combines rapidly and reversibly with o2
Hb + O2 <–> HbO2

Question 7

give ex of how Hb helps

Answer 7

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%

Question 8

does o2 bound to hb contribute to po2 of blood, explains

Answer 8

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

Question 9

describe HbO2 dissociation curve

Answer 9

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

Question 10

what does Hb provide

Answer 10

automatic mechanism that matches tissues o2 supply to tissue need

Question 11

describe at low values of po2 - o2 dissociation curve

Answer 11

as seen in peripheral tissues
small drop in po2 unloads the o2 from the hb to the tissue

Question 12

give ex of drop in po2 - o2 dissociation curve

Answer 12

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%

Question 13

describe po2 - o2 dissociation curve graph

Answer 13

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

Question 14

describe climbing mount everest

Answer 14

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

Question 15

describe o2 dissociation curve o2 - total

Answer 15

total 02 = sum of o2 dissolved and combined with Hb
even at po2 600 - dissolved o2 = o2 dissolved in plasma is v small

Question 16

describe pathway of o2

Answer 16

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

Question 17

describe shape of hemoglobin dissociation curve

Answer 17

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

Question 18

describe shape of myoglobin dissociation curve

Answer 18

hyperbolic shape
desat only at very low partial pressures
safety mechanism = still have reserve of o2 at skeletal muscle level

Question 19

describe myoglobin

Answer 19

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

Question 20

what does total amount of o2 in blood mostly depend on

Answer 20

hb concentration

Question 21

describe under anemia conditions - o2 dissociation curve

Answer 21

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

Question 22

what is bohr effect

Answer 22

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

Question 23

describe bohr effect graph

Answer 23

hb desat at 50% - starts unloading earlier = now available for tissues
knows you are exercising = now need o2 available asap

Question 24

describe example of bohr effect

Answer 24

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

Question 25

what is opposite of bohr effect

Answer 25

reverse conditions = lower pco2, lower temp and increase ph

Question 26

describe carbon monoxide poisoning

Answer 26

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

Question 27

describe what happens in CO poisoning

Answer 27

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

Question 28

describe transport of co2

Answer 28

primary product of oxidative processes taking place in body cells
removed from tissues by the blood

Question 29

name the 3 ways co2 is carried in blood

Answer 29

physically dissolved in blood
combined with hb to form hbco2
as bicarbonate

Question 30

describe physically dissolved in blood - transport of co2

Answer 30

10%
carried as co2
physically dissolved

Question 31

describe combined with hb to form hbco2 - transport of co2

Answer 31

11%
combines with globin portion not heme
so no competition on hb

Question 32

describe as bicarbonate - transport of co2

Answer 32

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+

Question 33

describe transport of co2 through tissue capillaries

Answer 33

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

Question 34

describe reactions of transport of co2

Answer 34

all reversible
can proceed in either direction
depends on conditions like pco2

Question 35

what happens if co2 production increases

Answer 35

production of hbco2, hco3- and h+ increases
in peripheral tissues
but opposite happens at lung capillaries - equations move in opp dirs

Question 36

what happens when you lower blood pco2

Answer 36

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

Question 37

describe diffusion of co2 through pulmonary capillaries

Answer 37

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

Question 38

describe transport of co2 pathway

Answer 38

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

Question 39

describe graph of co2 content

Answer 39

co2 content = almost linear
not sigmoidal

Question 40

what is haldane effect

Answer 40

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

Question 41

describe haldane effect

Answer 41

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

Question 42

describe haldane effect graph

Answer 42

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

Question 43

describe co2 dissociation curve

Answer 43

co2 dissociation curve has not steep or flat portions
relationship between co2 content and pco2 = almost linear

Question 44

whats happens if hyperventilate - co2 transport

Answer 44

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

Question 45

whats happens if hypoventilate - co2 transport

Answer 45

means that if we hypoventilate and alveolar pco2 rises then arterial capillary and venous co2 also rise

Question 46

what does doubling alveolar ventilation do

Answer 46

doubling alveolar ventilation halves alveolar pco2 = follows that increase in alveolar ventilation proportionally increases co2 removal