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BIOL 364 > Final: Respiration 5 > Flashcards

Final: Respiration 5 Flashcards

1
Q

how is CO2 transported (3)

A
  • physically dissolved CO2 gas in plasma
  • CO2 bound to Hb
  • CO2 in bicarbonate for
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2
Q

CO2 transport: physically dissolved in plasma (2)

A
  • small amounts in this form (~5%)
  • CO2 is more soluble in body fluids than O2
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3
Q

CO2 transport: Hb-bound (2)

A
  • some in this form (5-23%)
  • eg. carbaminohemoglobin
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4
Q

CO2 transport: bicarbonate form (3)

A
  • most in this weak base form
  • CO2 + H20 <–> carbonic acid <–> bicarbonate (HCO3-) + protons
  • reaction catalyzed by carbonic anhydrase
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5
Q

carbonic anhydrase

A
  • reduces half time of bicarbonate reaction from 60-90s to a milliseconds
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6
Q

bicarbonate reaction simplified

A

CO2 + H20 <–> HCO3- + H+

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7
Q

why is carbonic acid usually excluded from the bicarbonate formation formula

A
  • it basically does not exist because its is metabolized so quickly
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8
Q

Henderson Hasselbalch equation (2)

A
  • HA <–> H+ + A-
  • weak acid <–> protons + anions
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9
Q

Henderson Hasselbalch formula (2)

A
  • pH = pK’ + log ([A-]/[HA])
  • pK’ is negative log of the acid-dissociation constant
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10
Q

pK’ = pH

A
  • half of the weak acid is dissociated and physically dissolved, half exists as the weak acid
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11
Q

Henderson Hasselblach formula: CO2 (2)

A
  • CO2 is a gas, so total dissolved CO2 = PCO2 x CO2 solubility (Bunsen solubility coefficient, alpha)
  • pH = pK’ + log ([HCO3-]/ alpha * PCO2)
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12
Q

pK’ and pH: CO2 (2)

A
  • pK’ of CO2 is ~6.1
  • blood pH is 7.4-7.8
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13
Q

pK’ and pH: CO2/HCO3- percentages (2)

A
  • pH is a bit more than 1 pH unit greater than pK’ for reaction
  • 95% of total CO2 is HCO3- and only 5% is physically dissolved CO2
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14
Q

dissolved CO2 vs HCO3- (2)

A
  • HCO3- is not very permeable across membranes
  • CO2 is permeable across membranes
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15
Q

RBC level: CO2 from tissues into the RBC (3)

A
  1. physically dissolved CO2 diffuses down partial pressure gradient from tissues to blood
  2. CO2 diffuses into RBCs
  3. CO2 left in plasma is converted SLOWLY into bicarbonate as carbonic anhydrase is not present outside RBC
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16
Q

RBC level: CO2 from tissues inside the RBC (3)

A
  1. CO2 dissociates to HCO3- + H+ due to high carbonic anhydrase levels in RBC
    2 Chloride shift: as RBC HCO3- increases, HCO3- exits RBC in exchange for Cl-
  2. HCO3- is stored in the plasma for transport
17
Q

RBC level: CO2 from tissues interacting with Hb inside the RBC (2)

A
  1. protons released in bicarbonate reaction stabilize the “T state”, driving O2 off Hb
  2. as Hb becomes deoxygenated, carbamino complexes (bound CO2) and H+ are bound by Hb (Haldane effect)
18
Q

how do RBCs contribute to loading CO2 from the tissues into the blood (2)

A
  • keep RBC H+ and HCO3- levels low
  • CO2 can continue to enter blood, removing it from tissues
19
Q

RBC level: CO2 from RBC to environment

A
  1. physically dissolved CO2 diffuses down its partial pressure gradient from blood to the air/water
20
Q

RBC level: CO2 from RBC to environment; inside the RBC (2)

A
  1. removal of CO2 causes carbonic anhydrase to convert HCO3- and H+ into H20 and CO2 in RBC
  2. chloride shift: as RBC HCO3- falls, HCO3- enters RBC in exchange for Cl-
21
Q

RBC level: CO2 from RBC to environment; Hb and CO2 (2)

A
  1. as Hb becomes oxygenated, carbamino complexes (bound CO2) and H+ are released from Hb (Haldane effect)
  2. H+ combine with RBC HCO3- to permit continued CO2 excretion until RBC leaves respiratory epithelium
22
Q

how does RBCs contribute to processes at the respiratory surface

A
  • O2 uptake facilitates CO2 removal in RBCs at the respiratory surface
23
Q

what is the rate limiting step for CO2 excretion

A
  • chloride shift
24
Q

carbon dioxide equilibrium curve

A
  • relationship between PCO2 and total CO2 content of the blood
25
Q

Haldane effect: CO2 levels (3)

A
  • for a given PCO2, the more H+ buffered, the greater the total CO2
  • deoxygenated blood binds H+ to Hb, driving rxn to further create HCO3-
  • deoxygenated blood carries more CO2 than oxygenated blood
26
Q

Haldane effect: CO2 unloading perspective (2)

A
  • when deoxygenated blood is oxygenated, it elevates PCO2 and enhances CO2 removal
  • Hb binds O2 and frees H+
27
Q

Haldane effect: CO2 loading perspective (2)

A
  • as oxygenated blood enters tissues, unloading of O2 allows blood to hold more CO2 for same given PCO2
  • facilitates CO2 removal from tissues into blood
28
Q

Hb levels in RBCs
- levels
- risks

A
  • Hb levels in RBC s are very high, on the verge of solubility in the RBC
  • sickle cell anemia is result of Hb levels beyond solubility limit and crystallizing
29
Q

CA levels in RBCs

A
  • present at high levels to rapidly and reversibly convert CO2 to HCO3- and vice versa
30
Q

HCO3-/Cl- exchanger level in RBCs

A
  • high levels to allow most CO2 to be transported in the plasma as HCO3-

BIOL 364 (44 decks)

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