(14) Gas Transport

Question 1

he added a lexicon that isn’t in the slides - if you decide to look into that

Answer 1

Question 2

(Oxygen Transport in the Circulation)

1. O2 is carried in the blood in what two forms?
2. What is the solubility of O2?
3. At PaO2 of 100 mmHg, what is the concentration of dissolved O2?
4. Is dissolved O2 suffiecient to meet tissue demands?
5. What percent of O2 in blood is bound to hemogloblin?
6. What is hemoglobin when it is bound by oxygen? when it isn’t?

Answer 2

1. dissolved and bound
2. 0.003 ml O2/100 mL bloog/mm Hg
3. 0.3 mL/ 100 mL
4. no, not even close
5. 98%
6. oxyhemoglobin (+O2): deoxyhemoglobin (-O2)

Question 3

(Properties of Hemoglobin)

1. Hemoglobin - how many globin chains, heme moieties, and Fe2+?
2. Each subunit can bind how many O2s?
3. What is hemoglobin A? What is is composed of?
4. Hemoglobin F?
5. What happens in Fe is converted from ferrous 2+ to ferric 3+? What is this form called? What cleaves this and returns to normal?
6. What is the shape of oxygen binding curve? What O2 pressure is there a dramatic increase in binding? What type of binding is this? What allows this?

Answer 3

1. 4 each
2. one
3. Adult form, alpha2beta2 polypeptide chains
4. Fetal form, alpha2gamma2 chains
5. won’t be able to bind O2; methemoglobin; methemoglobin reductase
6. sigmoidal; 30-40 mmHg; positive cooperativity; changes in steric hindrance

Question 4

(Methemoglobinemia)

• Fe2+ Heme vs Fe3+ ?
• (Etiology - study of causation) What can cause this (3 things)
• What genetic definiency causes this?

Answer 4

• Fe2+ will bind O2 (hemoglobin) and Fe3+ won’t (methemoglobin)
• anesthetic sprays, sulfonamides, nitrites
• methemoglobin reductase deficiency

Question 5

(Hemoglobinopathy)

1. What is Hemoglobin S?
2. What type of chains and what does this cause?
3. What causes this mutation?
4. What does this mutation result in?
5. What shapes are the erythrocytes and what does this cause?

Answer 5

1. Variant of Hb that causes sickle cell disease
2. alpha-A2-beta-S2 chains – low affinity for oxygen
3. AA substitution - glutamate for valine
4. abnormal protein folding tertiary/quarternary structure
5. sickle shape - cause occlusion of small blood vessels (painful)

Question 6

What is oxygen binding capacity?

What is oxygen content?

What is oxygen delivery?

Answer 6

• max amount of O2 bound to Hb
• O2 binding capacity * % saturation
• cardiac output * O2 content of blood

Question 7

1. % saturation of Hb is a function of what?
2. What is the shape of the curve?
3. What is the P50? What is this approximate pressure?

Answer 7

1. the PO2 of blood
2. sigmoidal, non-linear
3. The Pressure at which hemoglobin is 50% saturated with O2; 25 mm Hg

Question 8

(Right and left shift of O2)

1. What causes a shift to the right? When would this occur? Decreased or increased affinity for O2? What does this result in?
2. What causes a shift to the left? What form of Hemoglobin is shifted to the left? When would this occur?

Answer 8

1. increased PCO2, temp, 2,3-DPG and decrased pH;

lots of tissue metabolism (catabolism); decreased; more unloading of O2 to tissue

2. decreased PCO2, temp, 2,3-DPG and an increase in pH;

Hemoglobin F (fetal)

Hyperventilation

Question 9

What is the fact that there is a decreased affinity fo O2 at low pH at high CO2 called?

Question 10

2,3-DPG causes what kind of shift?

What does it bind to?

When it is used?

Answer 10

• to the right
• beta chains of deoxyHb and decreases affinity
• high altitude –> hypoxemia –> 2,3 DPG –> O2 unloading

Question 11

1. What kind of curve shift does carbon monoxide poisioning cause?
2. What does it do?
3. Why is this?

Answer 11

1. a shift to the left
2. Decreases O2 bound to hemoglobin
3. The Binding affinity of CO much greater than O2

Question 12

(Carbon Dioxide Transport in Blood)

1. What percent of CO2 is dissolved? Guided by what law?
2. What percent is bound (and to what)?
3. What percent as chemically modified gas (and as what)?

Answer 12

1. 5% - Henry’s Law
2. CO2 can be bound to hemoglobin (3%) (at the amino groups)
3. (>90%) as HCO3-

Question 13

What converts H2O and CO2 to bicarbonate?

What is done with the HCO3- once it is made?

Answer 13

• carbonic anhyrdrase
• stays bound to RBC or exchanged for Cl-

Question 14

(Role of CO2 in Acid-Base Balance)

Long Term (hours to days) Regulation of the Kidney

1. What does it?
2. What do they do?
3. How long to be effective?

Short term (minute-bu-minute) Regulation of Blood pH

4. What system does this?
5. How?

Answer 14

1. The kidneys
2. alter the secretion rate of hydrogen ions and the re-absoprtion rate of bicarbonate to control blood pH
3. weveral hours
4. respiratory system
5. variations in alveolar ventilation can be used to correct pH

Question 15

1. What is caused by a decrease in HCO3- concentration that, according to the Hendersen-Hasselbach equation, leads to a decrease in pH. What is an example?
2. What is caused by an increase in HCO3- concentration that, according to the Henderson-Hasselbalch equation, leads to an increase in pH. example?
3. What is caused by hypoventilation, which results in CO2 retention, increased PCO2 , and decreased pH. example?
4. What is caused by hyperventilation, which results in CO2 loss, decreased PCO2, and increased pH. example?

Answer 15

1. metabolic acidosis; diarrhea
2. Metabolic Alkalosis; vomiting
3. Respiratory Acidosis; hypoventilation
4. Respiratory Alkalosis; hyperventilation

Question 16

What is the mechanism of hypoxia in cyanide poisoning? How quick?

What are the consequences of porphyria in animals?

Answer 16

• competitive binding, the nittile has a high affinity for the O2 binding site on hemoglobin; very rapid
• have mutated poryphrins and aren’t able to bind O2 as well