lecture 18: oxygen transport in the blood Flashcards
how do we get oxygen from air into your cells
principle of diffusion
air composed of many gases
gas dissolved into liquids
gas exchange is the interaction of wht two systems
respiraotry and cardiovascular system
explain why the respiratory/cardiovascular systems interact in tnro to gas exchange
RBCs (in blood vessels) carry O2 and CO2
gas exchange occurs between what
Occurs between alveolar air and blood
– Across membranes: the blood-air barrier
rank the partial pressure of oxygen innn the arteries, alveoli and tissues
PAO2»_space; PaO2»_space; PO2 in tissues
since PAO2»_space; PaO2»_space; PO2 in tissues, this allows what
Allows O2 to diffuse from alveoli to blood to tissues
rank the partial pressure of carbon dioxide in the arteries, alveoli and tissues
PCO2 in tissues»_space; PaCO2»_space; PACO2
since PCO2 in tissues»_space; PaCO2»_space; PACO2, what does that allow in terms of diffusion
Allows CO2 to diffuse from tissues to capillary
blood to alveoli
gas exchange depends on what (2)
– Partial pressures of the gases
– Diffusion of molecules between gas and liquid
venous blood exits RV by what pathway
pulmonary trunk to
pulmonary arteries to
ramifications to
capillary network
oxygenated blood goes back to the heart via what
pulmonanry veins
true or false: oxygenated blood goes back to the heard via pulmonary artries
false, pulm veins
true or false: venous blood enters pulmonary capillaries at the arterial and exits at the venous end.
true
venous blood enters and exits at what end pulmonary capillaries
venous blood enters
pulmonary capillaries at the arterial and exits at the venous end.
ADD SLIDE ON LECT 18 SLIDE 5
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what happens to o2 requirement during exercise
can icnrease 20 fold
what two things happen in terms of uptake of oxygen by pulm cap blood during exercise
– O2 requirement can increase 20-fold
– Also, since heart rate increases. time that blood remains in pulmonary capillaries can dercease by half
is it a problem that during exercise
– O2 requirement can increase 20-fold
– Also, since heart rate increases. time that blood remains in pulmonary capillaries can dercease by half
no because we have an extensive backup system
what is the safety factor that allows us to combat the increase in 02 requirement during exercise
Safety factor of O2 diffusion through pulmonary membrane
– Oxygen diffusion capacity increases by ~ 3-fold
true or false, blood becomes almost saturate with 02 very quickyl?
true , blood becomes almost saturated
with O2 by the time it has passed 1/3 of the capillary
why is it not a problem that when heart tate increases, time that blood remains in pulm capilaries can decrease by half
because blood becomes almost saturated
with O2 by the time it has passed 1/3 of the capillary
– So during exercise, even if exposure time is reduced,
blood will still become fully oxygenated
in the pulm capillaries, the blood gets oxygenated slowly or quickly
very quickyl
what is the reasonn blood can never be 100% saturated with o2
because the blood mixes with pulmonary shunt blood (respiratory muscles deoxygennated blood mixes with oxygenated blood)
deoxygenation of the blood can only happen where
at the systemic capilarries
(diffused from blood to tissue(
the venous blood PvO2 depends on what
upon tissue metabolic activtiy
what ate the two ways that blood carries oxygen
1) in physical solution dissolved in the fluid portion of blood (3%)
2) in loose combo with hemoglobin (97%)
what is the function of transporting oxygen dissolved in the fluid portion of blood
– Establishes the PO2 of the plasma and tissue fluids
– Helps to regulate breathing
– Determines oxygen loading of hemoglobin in the lungs and subsequent release in tissues
is aprtial pressure of o2 in blood mesured by oxygen bound to hemo globinn or oxygen dissolved in fluid portionn of blood
bt oxygen dissolved in fluid portion of blood
explain how having oxygen dissolved in the fluid portion of blood can help to regualte breathing
because sensors can pick up o2 in solution to increase/decrese breathing rate
what is hemoglobin
the iron protein molecule within the RBC
=globular protein pigment
what is the major contnributor to oxygen transport
oxygen in loose combo with hemoglobin
oxygen combined with hemoglobin carries more or less oygen than normally dissolved in plasma
Carries 65-70 times more oxygen than normally dissolves
in plasma
each of the 4 iron molcules in hemoglobin can bind out many oxygen moleulces
1
1 02 per iron moecule
how many ooxygen molecules can each hemoglobinc carry
4 molecules of o2 (because of 4 iron molucles on hemo glib)
The partial pressure of
oxygen dissolved in physical solution dictates what
the
oxygenation of hemoglobin to oxyhemoglobin
what is cooperative binding
The binding of an O2 molecule to the iron atom in one of the four globin chains progressively facilitates the binding of subsequent
molecules
if 1 o2 binds to the hemoglobin, does that make it harder or easier to bind others
easier
as you lose 1 o2 molecule, does it imake it harder or easier to lose others
makes it easier
as each o2 binds to the hemoglobin, what happens
the hemoglobin “opens up”
=allows more oxygen to be exposed to the surface and easier binding
blood of normal person contains how much hemogloib
15 g of HB/ 100 ml of blood
each gram of Hb can bind with amax of how many O2
max 1.34 g of O2
what is the max ammount of o2 that can be carried by 100 ml of blood
20 ml
when is 20 ml o2/100 ml blood obtained
if Hb is
100% saturated with O2, and is known as 20 volume
percent
what is the volume percent o2
indicates the amount of O2 carried by 100 ml of blood at different % saturations
oxygenated blood leaving the lungs have a higher or lower saturation and what does that mean in terms of tje volume percent
higher saturaration therefore high volume percent
what is the PO2 of blood at venous end of tissue capilary
40 mmHG
after passing through
tissue capillaries, amount of O2
carried by blood in veins (CvO2) increased or reduced
is reduced to 14.4 ml of O2 for each 100 ml of blood (on average)
(from 20)
what is the avo2 difference
describes the difference between the
oxygen content of arterial blood and mixed-venous blood
difference between the the amount of oxygenated blood coming into tissue vs leaving
what is the AVO2 difference
Averages 4-5 mL of O2 per deciliter of blood
true or false: O2 release from hemoglobin can occur without any increase
in local tissue blood flow
true
explain this sentence:
“An active muscle’s uncompromising capacity to use available O2 in its large blood flow supports the position that O2 supply, not muscle O2 use, limits aerobic exercise capacity”
as long as we supply the oxygen with o2=muscle will use it if needed
limit: if not enough oxygen is available (CV system startts not being able to provide O2). avo2 differentce will increae to meet o2 needs
what can rapid use of o2 by tissue cells cause
in strenous exercise
can cause PO2 in interstitial fluid to fall from normal of
40 mmHg to as low as 15 mmHg
at a low po2 in intersticial fluid of 15 mmHG (after strenous exercse), how much o2 remains bound to HV in each ml of blood and what does this mean
4.4 ml O2
This means that the tissues used up more oxygen (higher oxygen diffusion into the working tissues to supply the increasing metabolic needs)
=larger AVo2 diff
during strenous exercise, is AV o2 difference greather or lower than normal
3x normal level, i.e. 3x more O2 is extracted in
from each volume of blood that passes
through tissues
a large utilaxationn coefficent = large BLANK
large avo2 difference
at rest, what is the utilzation coeeffient
25% (5 ml of o2/100 ml blood over possible max of 20)
75% of the o2 is still bound and does not get used up by tissues
during strenous exercuse, what is the utilazation coefficint
greater than 75% (15/20)
means that alot of the oxygen is getting diffused to working tissues
what are 4 Factors That Shift the Oxygen
Dissociation Curve to the right
(less hemoglobin saturation)
1) incnrease hydrogen atoms
2) increase co2
3) increase temp
4) increase BPG
what are the 2 metabolic factors that shift the oxygen dissocaition curve
effect of ph
effect of co2 in blood
what is the effect of PH on oxygen dissocaiteion cruve
After metabolism, there is a
Decrease in pH or increase in H+ (acidosis) which shifts the O2
dissociation curve to the right
• Decrease of pH from 7.4 (normal level) to 7.2 leads to ~15% decrease of hemoglobin saturation with O2
=more oxygen being dropped off to tissue, less o2 in the blood
explain the effect of carbon dioxide on the oxygen disscoation curve
Increase of CO2 in blood or increase of PCO2 (hypercapnia) leads to shift of O2 dissociation curve to the right
(moves equilibrum curve to make more H)
what is the bohr effect
result of changes in blood acidity and PCO2
and affects Hb’s O2 binding affinity
=hemoglobin has a lower affinity for 02 secondary to incrases in PCO2 or decreases in pH (incrase H)
=this increase the 02 being unloaded in order to meet o2 demand
what is the bohrs effect in the tissues
rightward shift of O2 dissociation curve
caused by increase of CO2 (and PCO2) and a
decrease in pH of blood
• Enhances release of O2 from blood in tissues
what is the bohrs effect in the lungs
curve is shifted to the left as
blood PCO2 drops and pH increases
• Enhances oxygenation of blood in lungs
explain the effect of body/tissue temp of the oxygen dissociateing cruve
increase in core temp leads to rightward shirt in the curve
=lower hemoglobin saturation
=unloading more o2 for the tissues beacuse heat is a sign of metabolism
explain why during exrecise, even if exposure time of blood to the alveoli is reduced, we can still get fully oxygenated blood ?
because during exercise, oxygen diffusion will increase by 3 fold
(o2 can more easily pass though the pulmonary membrane)
what does the partial pressure of oxygen in venous blood in tissues depend on
depends on tissue metabolic activtiy,
if greater metabolic need=great avo2 difference
explain the oxyhemoglobin dissocaitionn curve!!!
s,mfnajsf
what does it mean if you are at 20 volume percent
if you carry 20 ml of 02/100 ml of blood that means the hemoglobin is 100% saturated with o2 and is known as the 20 vol percent
=never happens because shunt
o2 gets reased when
02 gets released from Hb as systemic arterial blood flows through tissues
the blood leaving the lung has a higher or lower volume percent than the blood returning from the tissues
it has a higher hemoglobin saturation (ie. higher volume percent(
after oxygen unloading at the tissue level, do we unload all of it?
no , at the venous level, the %Hb saturation is still 75% which means we only lost about 5 ml of o2 in the blood and the rest returns to the
is our AV o2 difference always the same (around 5ml)
no , it can increase (greater diff) during exrecise which means we are unloading/diffusing more oxygen to the tissues
explain how 02 release from hemoglobin can increase withouht any increase in local tissue blood flow
just by changing the oxygen diffusion into the tissues
The amount of o2 rleased to the muscles is amost 3 times above the normal supply at rest
if there is a high body temp, do we unload more 02 or do we keep more o2 bound
we geet rid of o2 easier
what happens to hemoglobin saturation with a decrease in tissue temp
a decrease in tissue temp leads to an increased hemoglobbin saturation with 02 (keep more oxygen bound to the blood)
how does a red blood cell derive its energy what was does that mean in terms of waste products
A red blood cell derives its energy solely from the anaerobic
reactions of glycolysis because they contain no mitochondria,
causing them to produce the compound 2,3-diphosphoglycerate
(2,3-DPG)
explain the effect of 2,3 diphosglycerate in the blood and that affect on hemoglobin saturation with o2
as a reselt of RBC anerobic glycolis, 2.3 is formed and binds with hemoglobin
=reduced the affinity of oxygen allowing for greater oxygen release to the tissues because of a decrease in PO2
during exrecise is the compound 2,3 DPG helpful or harmful
it is helpful
it is a waste product of glycolysis of RBC
=it will bind with hemoglobin
=it will decrease affinity for 02
=o2 will more easilty be released which aids in oxygen transfer to the muscles
what accelerates 2,3 DPG in the blood
during exercise, heat acceleates glycolysis (formation of ATP from glucose) threfore increases the levels of DPG in blood which aids in oxygen transfer to muscles
if the oxygen dissocaiteion curve shifts to the right, what does that mean in term of hemoglobin saturation
it decreases (Drop off oxygen easier)
what is the affect of hypoxia on oxygen dissocaiton curve (hemo globin saturation with o2)
In hypoxia condition (lasting longer than a few hours), lack of O2
in tissues promotes production of DPG in blood à O2
dissociation curve shifts to the right à decreased hemoglobin
saturation with O2
• Causes O2 to be released to tissues at much higher PO2 levels
(as much as 10 x higher); can become an important adaptive
mechanism to hypoxia, e.g. if poor tissue blood flow
during exercise, what are some reasons the oxygen dissociation curve would shift to thee right (release o2 from blood HB to tissues)
1) exercising muscles release large quantities of CO2
2) increase in H+ (decrease pH) in muscle caps
3) incrase in muscle temp
4) release of 2.3 GPD
true or false: fetal hemoglobin has a strog affinity for o2
true
does fetal globin movee the curve to the right or left (o2 diss curve)
Fetal hemoglobin has strong affinity for O2 and therefore, shifts
O2 dissociation curve to the left
explain the effecet of sickle cell on oxygen dissociateion curve
Sickle cell (abnormal type of hemoglobin (HbS)) binds O2 like
normal hemoglobin, but sickle cells have greater 2,3
diphosphoglycerate (DPG), therefore it shifts O2 dissociation
curve to the right
what is myoglobin
An iron-containing globular protein in skeletal and cardiac
muscle fibers
what is the function of myoglbin
provides intramuscular oxygen storarage (binds and stores o2 in thee muscles for later use)
what types of musclese have more myoglobin
slow twitch
if a msucle is dark red, does it have more of less myoglobin
more
true or false: hemoglobin and myogolbin are the esame
Resembles hemoglobin because it also combines reversibly
with oxygen but each molecule contains one iron atom while
hemoglobin contains four
what is the main diff between hemoglobin and myoglobin
each molecule of myoglobin contains one iron atom while
hemoglobin contains four
true or false: myoglobin removes oxygen from the myscle
false, it adds additional oxygen to the muscle
true or false: myoglobin will only release o2 at very low o2 pressures
true
when does myoglobin facilitate oxygen transfer
Myoglobin facilitates oxygen transfer to the mitochondria when
exercise begins and during intense exercise when cellular PO2
declines rapidly
what is the oxygen saturation of myoglobin at rest and mod exercise
maintains high saturation
explain the difference between the oxygen saturation curve for hemoglobin vs myoglobin
Compared with the oxygen saturation curve for hemoglobin,
the curve for myoglobin shows that it much more readily binds
and retains oxygen at low PO2
true or false: the greatest oxygen releases frm myoglobin happen at high levels of partial oxygen
false, the greatest quantity of oxygen release from myo occurs when tissue PO2 declines below 5 mmHG (VERY LOW)
what is the affect of acidity, co2 and body temp on myoglobin
Acidity, carbon dioxide, and temperature do not affect
myoglobin’s oxygen-binding affinity
explain the po2 difference in the arterial blood vs in the tisues
When arterial blood reaches peripheral tissues, PO2 is still
~95 mmHg, while PO2 in interstitial fluid surrounding tissue
cells is only 40 mmHg
• I.e. tremendous initial O2 pressure difference (95 – 40 = 55)
• This causes O2 to diffuse rapidly from capillary blood into
tissues
• PO2 in capillaries will then fall (fast since O2 diffusion into
tissue occurs rapidly)
• So blood leaving tissue capillaries and entering systemic
veins will have PO2 of ~ 40 mmHg
why does the partial presure of oxygen drop drastically when going from air and then to the alveoli
1) we add water vapour to the air which must decrease the PO2
2) the residual vol of o2 in lungs is continuously being used in exhale and inhale (partial pressure of o2 must decrase in air because theres already oxygen in lungs)
why is there a slighy decrease in partial pressure of 02 when going from alveoli to the arterial
because of the shunt
=respiratory muscles consuemee some o2 and mix with fully saturated 02 which will decerase ethe partial pressure of o2 slightlt
what is the affect of blood flow on oxygen pressure in the intersituatl fluid pressure
Increased blood flow=
=Increased O2 transported into tissue fluid
=Increased PO2 in interstitial fluid
what is the affect of o2 consumption of oxygen pressur ein the intersital fluid
Increased tissue metabolic rate
=Increased O2 consumption
=Decreased interstitial fluid PO2
why is intraceellcular po2 usually low
because 02 is continuously being used up from tissue cells
true or false: we need a high intracellular o2 pressure to maintain metabolic oxygen demand for tissues
false, In normal resting conditions, only 1 to 3 mmHg of intracellular O2 pressure is
required for tissue cells to fully support the metabolic oxygen demand. Average
intracellular PO2 = 23 mmHg thus provides a large safety factor.
cells need how much po2 to maintain normal demand
Cells only need a PO2 of 1 mmHg for normal intracellular
chemical reactions to occur (i.e. O2 is not a limiting factor to
rates of chemical reactions at cellular PO2 > 1 mmHg)
what is the main limited factor to ratse of chemical reactions at cellular po2 and explain
Main limiting factor is cellular concentration of adenosine
diphosphate (ADP)
• When adenosine triphosphate (ATP) is used in cells to
provide energy, it gets converted to ADP
• Rate at which ADP is formed from ATP (i.e. rate of energy
expenditure within cell) is what controls rate of O2 usage by
cells under normal operating conditions
if atp/adp is greater than 1 what doese that mean in terms of o2
Plenty of ATP is available
– Tissue will not consume additional quantities of O2 for
producing ATP
if atp/adp is less than 1 what does that mean in terms of 02
– Relatively more ADP than ATP is present
– More O2 will be consumed to raise the ATP level
if ADP levels increase, does rate of o2 consumption increase or decrease
inncrease
what are the transport factors that affect oxygen comsumption at the tissue leevel
- Blood flow
- Perfusion pressure
- Capillary resistance
- Hemoglobin
what are the metabolic factorst that affect oxygen connsumption at the tissue level
Tissue activity
• State of conditioning
• Number and size of mitochondria
