Phys - Transport of CO2/Acid-Base Balance

Question 1

Normal rate of CO2 production

Answer 1

200 ml/min

Question 2

3 ways in which CO2 is transported in blood

Answer 2

1. Dissolved
2. Carbamylation to protein
3. Bicarb

Question 3

Is more O2 or CO2 dissolved in blood? Why?

Answer 3

CO2; higher solubility; C=alpha*P

Question 4

Two proteins to which CO2 is most often carbamylated

Answer 4

Hb and albumin

Question 5

What functional group binds CO2 during carbamylation?

Answer 5

-NH2

Question 6

How does O2 binding to Hb differ from CO2 binding?

Answer 6

O2 binds to Fe2+ of heme, while CO2 binds to -NH2 of heme

Question 7

Where does CO2 from bicarb? Why?

Answer 7

RBC; plasma doesn’t have carbonic anhydrase

Question 8

Which transport mechanism of CO2 predominates?

Answer 8

Bicarb

Question 9

In blood, O2 mainly transported as ___ while CO2 mainly transported as ___

Answer 9

HbO2; bicarb

Question 10

Rate limiting step in CO2 transport

Answer 10

Hydration (CO2+H2O –> H2CO3)

Requires CA

Question 11

Explain process of CO2 transport from tissue to blood

Answer 11

1. CO2 diffuses across tissue and RBC membranes (some dissolves in blood)
2. CO2 is hydrated via CA once in RBC, forming HCO3- and H+
3. H+ buffered by deoxyHb
4. HCO3- forced out of cell since H+ not available to form carbonic acid
5. HCO3- exchanged for Cl-/H2O to keep charge balance

Question 12

What is Hamburger’s phenomenon?

Answer 12

Cl- that enters RBC in exchange for HCO3- drags water with it, causing RBC to swell

Question 13

Name of HCO3-/Cl- anion exchange protein

Answer 13

Band three protein

Question 14

Why does H+ bind deoxyHb? What other effect does this have?

Answer 14

To prevent acidification of RBC

Right shifts O2-Hb curve

Question 15

Majority of H+ in venous blood carried as:

Answer 15

Bound to deoxyHb

Question 16

Describe process of CO2 transport from RBC to lung

Answer 16

1. CO2 dissociates from carbaminohemoglobin
2. HCO3- reenters cell and forms CO2 with dissociated H+
3. CO2 diffuses across RBC and alveolar membranes
4. CO2 exhaled

Question 17

Hb has more affinity for CO2 or O2?

Answer 17

CO2 (which right shifts O2-Hb curve)

Question 18

Difference between CO2 and O2 dissociation curves:

Answer 18

CO2 curve is:

1. Steeper (small change in PCO2=massive change in CO2 content)
2. Higher (more CO2 in blood than O2)
3. Linear (changes in PCO2 over broad range have same effect on CO2 content; no cooperativity)

Question 19

Haldane effect

Answer 19

Changes in O2 saturation of Hb will shift CO2 dissociation curve

Question 20

Left shift of CO2 curve means

Answer 20

Decreased O2Hb (more affinity for CO2)

Question 21

Right shift of CO2 curve means

Answer 21

Increased O2Hb (less affinity for CO2)

Question 22

Why does deoxygenation of blood left shift CO2 curve?

Answer 22

H+ can bind to Hb and CO2 binds Hb with greater affinity than O2

Question 23

What is the difference between Bohr effect and Haldane effect?

Answer 23

Bohr effect refers to H+ effect on shift of O2 curve

Haldane effect refers to O2 effect on shift of CO2 curve

Question 24

From right to left atrium, PO2 increases from 40-100 mmHg and PCO2 decreased from 46-40 mmHg. Respiratory quotient is 0.8 but a 6 mmHg change in PCO2 is matched with 60 mmHg change in PO2. How can this happen?

Answer 24

The CO2 curve is linear so small change in PCO2 = massive change in CO2 content. The O2 curve is sigmoidal, so the magnitude of the change in O2 content matches the magnitude of the change in CO2 content.

Question 25

What is the normal pKa of blood?

Answer 25

6.1

Question 26

H-H equation (both forms)

Answer 26

pH = pka + log[HCO3-}/[CO2]
pH = 6.1 + log[HCO3-]/0.03PCO2