O2 and CO2 Transfer Between Alveolus, Blood and Tissue Flashcards Preview

Human Epithelial Biology > O2 and CO2 Transfer Between Alveolus, Blood and Tissue > Flashcards

Flashcards in O2 and CO2 Transfer Between Alveolus, Blood and Tissue Deck (49)
1

What are the two ways oxygen can be carried in the blood?

Physical
Chemical

2

How is O2 carried physically in the blood?

plasma soluble (2%)
0.3ml O2/100ml blood

3

How is O2 carried chemically in the blood?

O2 bound to hemoglobin (98%)

4

How much O2 does Hb bind?

1.34ml

5

How much hemoglobin is there per 100ml blood?

15g

6

What is the O2 carrying capacity of Hb?

20mls O2/100ml

7

What is the total arterial content of O2?

20 + 0.3ml = 20.3 ml O2/100ml blood

8

What is the total venous O2 content?

O2 carrying capacity is 15mls/O2/100mls and plasma soluble 0.28mls
15.28ml O2/100ml blood

9

How are SaO2 calculated?

Oxyhemoglobin/O2 carrying capacity of Hb

10

What is the problem with SaO2?

it can remain the same even if the O2 content of the blood differs i.e. anemia or polycythemia

11

What is the P50 value on the oxygen dissociation curve?

the PO2 required for half maximal Hb saturation

12

What saturation does venous blood enter the alveolus?

75%

13

What does the arterial plateau phase ensure?

maximal HbO2 saturation even if alveolar PO2 is below normal

14

What does the steep phase of the curve favour?

offload of arterial oxygen to tissues

15

What happens when there is a left shift in P50 for the ODC?

increased Hb-O2 affinity and reduced offloading to tissue

16

Where might a left shift in the ODC be seen?

fetal Hb

17

What happens when there is a right shift in P50 for the ODC?

decreased Hb-O2 affinity and raised offloading to tissues

18

Where might a right shift in the ODC be seen?

high altitude

19

What may cause a right shit in the ODC?

stressors such as acidosis, fever and hypoxia

20

Describe the structure of hemoglobin

heterotetramer with 2a and 2b subunits
4 iron binding heme domains
O2 reversibly binds the Fe3+ ions in the centre of the heme ring

21

What alters the affinity of hemoglobin for O2?

CO2
2,3 BPG
interact with charged amino acids between the a and b subunits

22

What does hemoglobin require for each 2O2 released?

H+ ion

23

What interaction is pH and O2 sensitive?

amino terminus of a subunit binds b-carboxyl terminal histidine stabalising Hb structure

24

What happens to the interaction a physiological pH?

O2 binding to heme can release the protons to produce Oxy-Hb

25

What happens to the interaction in acidosis?

decreased pH favours the a-b subunit interaction and reduces the binding of O2 to heme

26

What are the two ways increased blood pCO2 releases O2 from Hb?

production of carbonic acid in red cell
Carbamate reaction at the N-terminal amino groups on the Hb a-subunit

27

What is the reaction produced for carbonic acid?

CO2 + H2O -> H2CO3 -> HCO3 + H

28

What is the reaction produced for carbamate reaction?

CO2 + R-NH2 -> R-NH-COO + H

29

What is the overall effect of increased blood pCO2?

acid stabilisation of a-b B subunits and a low affinity for O2

30

What are the other factors affecting O2 transport?

Carbon monoxide - far greater affinity than O2 - HbCO, causing left shift
Anemia - O2 carrying capacity is lowered - shift right

31

What PO2 does fetal development occur at?

30mmHg

32

What ODC does the fetus have compared with the mother?

left shifted ODC - so high affinity for O2

33

How does the fetus allow for O2 off-loading?

very low PO2 at tissues

34

What Hb subunit is expressed during fetal development and when does this change?

y subunit
replaced at birth by bHb

35

What are the physical forms of CO2 in the blood?

Soluble CO2 5%
Bicarbonate ion 90%

36

What is the chemical form of CO2 in the blood?

carbamino hemoglobin

37

What is the amount of CO2 exhaled?

4ml CO2/100ml blood

38

How is the plasma pH buffered by the red cell?

HCO3 moves out of the red cell to maintain CO2 gradient and plasma pH

39

What is the Haldane effect?

Where deoxygenation of blood improves carriage of CO2

40

What is the first stage in CO2 release from tissue and O2 release from the RBC?

CO2 dissolves into plasma and red cell along partial pressure gradient

41

What is the second stage in CO2 release from tissue and O2 release from the RBC?

low tissue O2 favours CO2 carriage by blood - HALDANE

42

What is the third stage in CO2 release from tissue and O2 release from the RBC?

Carbamate reaction reduces HbO2 affinity - BOHR

43

What is the fourth stage in CO2 release from tissue and O2 release from the RBC?

Carbonic anhydrase reaction generates carbonic acid which protonates. HCO3 leaves cel and maintains CO2 gradient

44

What is the final stage in CO2 release from tissue and O2 release from the RBC?

Increased H in RBC reduces HbO2 affinity - BOHR

45

What is the first stage in CO2 release from RBC and O2 release from the Alveolus?

O2 dissolves into plasma along partial pressure gradient

46

What is the second stage in CO2 release from RBC and O2 release from the Alveolus?

High affinity of Hb for O2 reverses carbamation and protonation raising availability of high affinity Hb - BOHR

47

What is the third stage in CO2 release from RBC and O2 release from the Alveolus?

CO2 diffuses into alveolus according to partial pressure gradient. High PO2 reduces CO2 affinity for Hb - HALDANE

48

What is the fourth stage in CO2 release from RBC and O2 release from the Alveolus?

Movement of CO2 out of RBC increases HCO3 uptake

49

What is the final stage in CO2 release from RBC and O2 release from the Alveolus?

Proton release from Hb and increased HCO3 drive reverse carbonic anhydrase reaction and maintain outward CO2 gradient and lower plasma bicarbonate