Resp_L05_Flashcards

Question 1

What is meant by positive cooperativity of hemoglobin?

Answer 1

Hb binds O2 poorly at low concentrations. Once there is enough O2 to bind alpha subunits, a conformational change results and Hb binds O2 much more efficiently. I.e. Hb binds O2 well at high concentrations.

Question 2

What is Hb’s affinity to O2 in the T form? In the R form?

Answer 2

T form: low affinity; R from: high affinity

Question 3

What three factors reduce oxygen affinity of Hb (stabilize T form)?

Answer 3

Low pH; 2,3-BPG binding; high CO2 concentrations

Question 4

Describe the Bohr effect.

Answer 4

High H+ and CO2 lead to decreased O2 affinity of Hb (Hb lets go of O2 where the environment is acidic or where there is a lot of CO2).

Question 5

What are the three forms of carbon dioxide in the blood? Formation of which two forms of carbon dioxide generate H+?

Answer 5

Three forms: dissolved, attached to hemoglobin as carbamages, and bicarbonate ions. Formation of carbamates and bicarbonate ion generate H+.

Question 6

What is the Haldane effect?

Answer 6

States: deoxygenated Hb has increased ability to carry CO2 and vice versa.

Question 7

Describe how Hb functions in the vicinity of working muscle.

Answer 7

Working muscle is producing CO2 –> combines with water in presence of carbonic anhydrase –> forms carbonic acid –> dissociates into bicarbonate and proton –> proton binds to Hb and reduces oxygen affinity –> O2 unloads into working tissue.

Question 8

Describe how Hb functions in the lungs.

Answer 8

Increased O2 in lungs –> O2 loads onto Hb –> conformational change –> break salt bridges and release proton –> proton combines with bicarb to form carbonic acid –> carbonic acid combines with water in presence of carbonic anhydrase to form CO2 –> CO2 blown off in lungs.

Question 9

What is the Henderson-Hasselbalch equation for the bicarbonate buffer system?

Answer 9

pH = 6.1 + log ([HCO3-] / (0.03)PCO2)

Question 10

How does hypoventilation affect pH?

Answer 10

Accumulation of CO2 –> increased H+ –> decreased pH

Question 11

How does hyperventilation affect pH?

Answer 11

CO2 blown off –> decreased H+ –> increased pH

Question 12

What do respiratory pH imbalances result from?

Answer 12

Changes in PCO2.

Question 13

What do metabolic pH imbalances result form?

Answer 13

Changes in [HCO3-].

Question 14

What is the most important blood buffer besides the bicarbonate buffer system?

Answer 14

Hemoglobin (picks up or lets go of protons leading to increased or decreased formation of bicarbonate).

Question 15

How does respiratory compensation for alkalosis/acidosis manifest? Is it fast or slow?

Answer 15

Hypo- or hyperventilation; fast (hours).

Question 16

How does renal compensation for alkalosis/acidosis work? Is it fast or slow?

Answer 16

Production/excretion of bicarbonate and excretion of H+. Slow (days).

Question 17

How does the body compensate for metabolic acidosis?

Answer 17

Hyperventilation (make sure to look at diagrams on slides 24 - 27; might test on how the dots move).

Question 18

How does the body compensate for respiratory acidosis?

Answer 18

Kidneys secrete HCO3- (increase blood HCO3- concentrations) (make sure to look at diagrams on slides 24 - 27; might test on how the dots move).

Question 19

How does the body compensate for respiratory alkalosis?

Answer 19

Kedneys excrete HCO3- (decrease blood HCO3- concentrations) (make sure to look at diagrams on slides 24 - 27; might test on how the dots move).

Question 20

How does the body compensate for metabolic alkalosis?

Answer 20

Hypoventilation (make sure to look at diagrams on slides 24 - 27; might test on how the dots move).

Question 21

A patient presents after almost drowning with the following lab values: low pH, high PCO2, high lactate, and low HCO3-. How would you treat this patient?

Answer 21

Mechanical hyperventilation (correct respiratory acidosis). Metabolic acidosis (low bicarb) will correct itself over time.