Gas Transport by the Blood

Question 1

Inspired air is heated and humidified to 100%- what is the partial pressure of water vapor in inspired air?

Answer 1

47 mmHg

Question 2

How is oxygen carried in the blood?

Answer 2

It is physically dissolved in the plasma and it is chemically combined with hemoglobin

Question 3

What is the typically amount of O2 in 100 mL of blood?

Answer 3

0.3 mL

Question 4

When fully saturated, how much oxygen can one gram of hemoglobin?

Answer 4

1.34 mL

Question 5

True or False: Hemoglobin is typically 100% saturated with oxygen

Answer 5

False- it is normally 97.4% saturated

Question 6

What is the maximum amount of oxygen that can be chemically combined with hemoglobin in 100 mL of blood

Answer 6

20 mL

Question 7

True or false: Typically there is no oxygen in venous blood?

Answer 7

False

Question 8

What is the P50 of the dissociation curve?

Answer 8

The partial pressure of gas at which the Hb is 50% saturated

Question 9

How does decreased pH affect the binding of oxygen to Hb? How does this affect the oxygen dissociation curve?

Answer 9

If the pH is lower, the curve shifts to the right, P50 is increasing meaning at the same PO2, at a lower pH, Hb carries less oxygen

Question 10

What is the effect of decreasing CO2 on the oxygen dissociation curve?

Answer 10

Lower PCO2 shifts the curve to the left- lower CO2 increases Hb binding to oxygen

Question 11

What is the Bohr effect?

Answer 11

It says that at the same PO2, if PCO2 is high or pH is low, Hb carries less oxygen

Question 12

How does temperature affect the oxygen dissociation curve?

Answer 12

Higher temperatures shift the curve to the right

Question 13

What is the effect of adding 2,3-BPG on an oxygen dissociation curve?

Answer 13

Shifts to the right

Question 14

What is the oxygen dissociation curve of arterial blood relative to venous blood? Why?

Answer 14

The venous curve is shifted to the right because the pH is lower and the PCO2 and maybe temperature is higher

Question 15

How does carboxyhemoglobinemia or anemia change the oxygen dissociation curve?

Answer 15

The general shape of the curve is the same, but the maximum saturation is lower– curve is shorter

Question 16

What is the fetal Hb oxygen dissociation curve relative to adult Hb curves? Why does this make sense?

Answer 16

Fetal Hb is shifted to the left of adult Hb- higher affinity– fetuses’ have lower PO2 and the higher affinity is probably helpful in pulling oxygen across the placenta

Question 17

What is the dissociation curve of a single Hb subunit and of myoglobin relative to hemoglobin?

Answer 17

Both Mb and Hb subunit lose the sigmoidal shape of hemoglobin’s curve but are shifted to the left

Question 18

When does cyanosis occur?

Answer 18

When more than 5 grams of Hb/100 mLof arterial blood are in the “deoxy” state

Question 19

True or false: Absence of cyanosis does not rule out hypoxemia

Answer 19

True

Question 20

In what condition might cyanosis be present but not indicative of hypoxemia

Answer 20

Polycythemia

Question 21

How is carbon dioxide carried in the blood?

Answer 21

Physically dissolves in plasma (20x more than O2), forms carbamino compounds, and as bicarbonate

Question 22

What are carbamino compounds? How are they formed?

Answer 22

Compounds that are formed when oxygen combines with a terminal amine group on a blood protein (i.e., Hb)

Question 23

What percent of carbon dioxide is carried as carbamino compounds?

Answer 23

10-15%

Question 24

What is the reaction that converts CO2 to bicarbonate? What enzyme catalyzes this reaction?

Answer 24

CO2 + H2O–> H2CO3–> H+ + HCO3; catalyzed by carbonic anhydrase

Question 25

How does deoxyHb facilitate the transport of CO2 in the blood?

Answer 25

deoxyHb is a base and will take up the H+ produced in the carbamino compound and the carbonic anhydrase reactions and drive the equilibrium to the right