Respiratory 7

Question 1

Amount of oxygen bound to Hb depends on

Answer 1

Plasma O2 (RBC and cytosol PO2) and amount of hemoglobin

Question 2

What does plasma O2 determine

Answer 2

% saturation of Hb

Question 3

Plasma O2 is determined by

Answer 3

Alveolar PO2

Question 4

What does alveolar PO2 depends on

Answer 4

1, composition of inspired air
2. Alveolar ventilation rate
3. Efficiency of gas exchange (normal for healthy)

Question 5

What does the amount of hemoglobin determine

Answer 5

Amount of Hb binding sites

Question 6

What is the total number of Hb binding sites calculated from

Answer 6

Hb content per RBC x Number of RBCs

Question 7

What is anemia

Answer 7

Reduced carrying capacity of O2 in blood

Question 8

What is the amount of O2 bound to Hb at any given PO2 expressed as

Answer 8

Percent saturation of hemoglobin (for any given pO2, Hb is a certain % saturated)

Question 9

What determined the % saturation of Hb

Answer 9

PO2 that Hb is exposed to

Question 10

What type of cells can have a lower PO2

Answer 10

Active cells (curve steep)
Can be as low as 20mmHg but larger release of O2

Question 11

If PO2 100 how saturated us Hb

Answer 11

98.5%

Question 12

When does more significant changes in saturation begin

Answer 12

Po2 below 60 mmHg

Question 13

What physical factors alter hemoglobin’s affinity for O2

Answer 13

Levels of CO2, pH, temperature, 2,3-BPG

Question 14

Shift in hemoglobin saturation as a result in pH or CO2 change

Answer 14

Bohr effect

Question 15

What causes fast decreasing shift in pH

Answer 15

Active cells (max exertion)
- produces excess CO2, results in increased H+ and lactic acid in cytoplasm and extracellular space
- decrease pH, high acid, slight conformation in Hb

Question 16

What does high pH cause

Answer 16

Reduced H+ and structural change in Hb and change affinity

Question 17

What is CO2 readily converted into

Answer 17

Acid
H+ + HCO3

Question 18

What does increased CO2 production cause

Answer 18

1. CO2 readily binds Hb altering conformation (O2 released)
2. CO2 readily converted to acid

Question 19

What does increased heat at level of tissues cause

Answer 19

Conformational change in Hb leading to decreased affinity and more O2 dropped at active muscles

Question 20

What is the metabolic compound 2,3-BPG

Answer 20

A by-product of glycolysis in RBC’s

Question 21

What increases 2,3 DPG

Answer 21

Chronic hypoxia
RBCs release ATP during hypoxia

Question 22

How does ascent to high altitude (low PO2) and anemia affect 2,3 BPG

Answer 22

Increases production

Question 23

What oxygen binding properties do fetuses have to increase binding affinity of Hb

Answer 23

Two alpha, two gamma globin subunits

Question 24

What does the different oxygen binding properties facilitate

Answer 24

Uptake of O2 into fetus even when exposed to lower PO2

Question 25

Why is there lower PO2 fro fetus

Answer 25

No direct connection between mother and fetus
O2 lost in intervillous space

Question 26

What is the importance of removing CO2 from body

Answer 26

1. Elevated PCO2 causes acidosis
2. Abnormally high PCO2 depresses CNS causing confusion, coma, or death

Question 27

What does acidosis cause

Answer 27

Low pH leads to interruptions in hydrogen bonds and denaturing of proteins

Question 28

How much CO2 carried by venous blood is dissolved in plasma

Answer 28

7%
Even though co2 very soluble, cells produce too much for plasma to be capable of carrying

Question 29

Where does remaining 93% CO2 diffuse

Answer 29

Red blood cells
- 23% binds to hemoglobin HbCO2 (open sites after O2 released)
- 70% is converted to HCO3- (bicarbonate)

Question 30

What are 3 ways CO2 is transported

Answer 30

1. Dissolved in plasma 7%
2. Bound to hemoglobin 23% (in RBCs)
3. Converted to bicarbonate 70% (in RBCs)

Question 31

What does carbonic anhydrase do

Answer 31

Converts CO2 when in excess to HCO3 and H+
Hb picks up H+

Question 32

When HCO3 enters plasma why does in exchange for Cl

Answer 32

Ensures charge of RBC remains normal

Question 33

What is happens to CO2 in reverse reaction

Answer 33

CO2 unbind Hb and diffuses out of RBC
Carbonic acid reaction reverses, pulls HCO3 back into RBC converting back to CO2

Question 34

What 2 purposes does the conversion of CO2 to HCO3 serve

Answer 34

1. Provide additional means of CO2 transport from cells to lungs (can take up as much as possible without contributing to partial pressure)
2. HCO3 is available to act as buffer for metabolic acids, stabilizing body’s pH (binds to acids)

Question 35

What is the reaction involving carbonic anhydrase

Answer 35

CO2 + H20 <-> H+ + HCO3-
Excess CO2 ——>
Low CO2 <—————-

Question 36

What does the conversion of CO2 to HCO3 and H+ continue until

Answer 36

Equilibrium

Question 37

What mechanisms exist to ensure equilibrium is not reached for CO2 to HCO3 and H+

Answer 37

Remove HCO3 from RBC (Chloride exchanger)
Mop up excess H+. (Hb binds and buffers acid)

Question 38

What does Hb binding to excess H+ as buffer do

Answer 38

• prevents large changes in body’s pH

Question 39

What causes Hb to not be able to carry out as buffer

Answer 39

If blood CO2 too high Hb cannot soak up all the H+ and respiratory acidosis can result