Respiration - Lecture 4 Flashcards
The amount of dissolved gas carried by the blood is directly proportional to…
the partial pressure of the gas
What kind of amount of O2 is dissolved in the blood?
a very small amount
What is O2 linearly proportional to?
PO2
How much O2 is in 100 mL of plasma?
0.3 mL
O2 consumption is much ___ than what can be supplied from the amount dissolved in the blood
greater
What is the rate of consumption of O2 at rest?
300 mL O2/min
What allows whole blood to take up to 65 times as much O2 as plasma at PO2 of 100 mmHg?
hemoglobin
How much does hemoglobin constitute of the total weight of red blood cells?
1/3
How many subunits is hemoglobin made of?
4
What is each subunit of hemoglobin made of?
a heme joined to a globin
What does heme contain?
an Fe++ ion
What can one Fe++ ion bind?
1 molecule of O2
Why is Hb essential for the transport of O2 by blood?
because it combines rapidly and reversibly with O2
At PO2 of 100 mmHg, what is the total amount of O2 physically dissolved in the blood?
0.3 vol.%
At PO2, of 100 mmHg, what is the total amount of O2 bound to Hb?
19.5 vol.%
What is the total amount of O2 in arterial blood?
about 20 vol.%
Does the O2 that is bound to Hb contribute to the PO2 of the blood?
no
What kind of molecules are responsible for PO2?
molecules that are physically dissolved in the blood plasma
What does the PO2 of the plasma determine?
the amount of O2 that combines with Hb
What does the HbO2 dissociation curve determine?
the amount of O2 carried by Hb for a given partial pressure of O2
When is the HbO2 dissociation curve flat? What levels?
at high values of PO2, at alveolar levels
When is the HbO2 dissociation curve steep?
at low values of PO2, at peripheral tissue levels
What happens to the amount of O2 bound to Hb at high values of PO2?
they remain constant
How much does PO2 have to drop in order for HbO2 to drop significantly?
60 mmHg
What happens to Hb at high pressures?
it becomes saturated
What happens to Hb at low pressures? Why?
it becomes desaturated to supply oxygen to tissues (e.g. exercise)
What happens to HbO2 at low PO2?
it dissociates into Hb and O2 more readily
Why is there a significant drop in PO2 and %HbO2 at the tissue level?
because it is where metabolic processes happen and its to match tissue O2 supply to tissue O2 need
As blood enters the tissue capillaries, plasma PO2 is ___ than interstitial fluid PO2
greater
O2 readily diffuses across the capillary membrane into the ____
interstitial fluid
What happens to plasma PO2 and O2 when O2 readily diffuses across the capillary membrane into the ISF?
plasma PO2 decreases and O2 diffuses out of the erythrocytes into the plasma
What happens to the HbO2 when the erythrocytes PO2 decreases?
it dissociates into Hb and O2
After diffusing into the interstitial fluid, where does the O2 go?
into the cells
What determines the affinity of Hb for O2?
its quaternary structure
What increases the affinity of the second binding for O2?
the combination of the first heme in Hb with O2
What increases the affinity of Hb?
the conformational change as O2 binds to Hb
Where is myoglobin found?
in skeletal muscle
Myoglobin resembles Hb but binds only…
one O2 molecule
What shape is the O2 dissociation curve?
sigmoid shape
What shape is the O2-myoglobin curve?
hyperbolic
When does myoglobin release its O2 in a O2-myoglobin curve?
at very low PO2
What does the total amount of O2 in the blood depend on?
Hb concentration
How much is the normal amount of Hb in a person?
14 g/100 mL
How much Hb does someone who has anaemia have?
10g/100 mL
When does the Bohr Effect shift the HbO2 dissociation curve to the right?
when blood CO2 or temperature increases or blood pH decreases
What does it mean when the HbO2 dissociation curve shifts to the right?
for a given drop in PO2, an additional amount of O2 is released from Hb to the working tissues
When does the Bohr equation shift the HbO2 dissociation curve to the left?
when blood CO2 or temperature decreases or blood pH increases
What has an extremely high affinity for the O2 binding sites in hemoglobin?
CO
What reduces the amount of O2 bound to hemoglobin?
CO
What does CO do to the O2-hemoglobin curve?
it shifts it to the left
What are the 3 ways CO2 is carried in the blood?
- physically dissolved (10)
- combined with Hb to form HbCO2 (11%)
- as bicarbonate (79%)
Where does CO2 diffuse?
into the plasma where it is physically dissolved
What does CO2 combine with in Hb?
the globin portion
Why does CO2 combine with the globin portion and not the heme portion of Hb?
so that there is no competition for binding on Hb
What does CO2 combine with to produce carbonic acid?
water
What aids the diffusion of CO2 in the erythrocytes?
carbonic anhydrase
What are the 2 formulas for bicarbonate?
- CO2 + H2O -> H2CO3 (carbonic acid)
- H2CO3 -> HCO3 + H+
All of the reactions involved with CO2 are…
reversible
What happens to the production of HbCO2, HCO3, and H+ if the CO2 production increases?
they also increase
What happens to HCO3 when blood PCO2 decreases?
it gets transformed into H2CO3 and further into CO2 and H2O, and HBCO2 generating Hb and CO2
What are the two reactions that happen when the blood PCO2 decreases?
- H+ + HCO3 -> H2CO3 -> H2O + CO2
- HbCO2 -> H2O + CO2
Why is there a decrease in blood PCO2 when there is a net diffusion from the blood into the alveoli?
because the blood PCO2 is higher than alveolar PCO2
Hb free of O2 may combine with what?
H+
What is the reaction of the addition of H+ to Hb?
H+ + HbO2 -> HHb + O2
What is the preferred way to transport CO2 in the body?
HCO3
When Hb is free of O2 and combines with H+, it acts as a…
buffer
What happens when there is a presence of reduced Hb in the tissue capillaries?
it helps with the blood loading of CO2
When do you carry more CO2?
when your blood is deoxygenated
Which kind of blood can carry more CO2 than arterial blood?
venous blood
What influences the CO2 dissociation curve by shifting it to the right?
the O2 saturation of blood
