F7ii: Describe the movement of CO2 from cell to atmosphere

CO­2 moves passively down concentration gradients

Cell

  • Produced in mitochondria from aerobic metabolism
  • 200mL/min at rest

Blood

  • Diffuses from cells → blood
  • ~120L of CO2 in body!
  • Majority stored in bone matrix
  • 3L is transported in blood:
    • Dissolved gas
    • HCO3–
    • Carbamino compounds
  • Transport bound to Hb facilitated by HALDANE EFFECT

“deoxygenated Hb can transport more CO2 cf. OxyHb”

Carriage in Blood

Arterial

Mixed Venous

V-A Difference

Carbamino

Arterial

0.0017mmol/L

Mixed Venous

0.002 mmol/L

V-A Difference

30%

Dissolved

Arterial

1.2 mmol/L

Mixed Venous

1.4 mmol/L

V-A Difference

10%

HCO3–

Arterial

24.4 mmol/L

Mixed Venous

26.2 mmol/L

V-A Difference

60%

PCO2

Arterial

40mmHg

Mixed Venous

45mmHg

V-A Difference

mL/dL

Arterial

48mL/dL

Mixed Venous

52mL/dL

V-A Difference

Alveolar CO2

  • PCO2 47mmHg
  • Diffuses from pulmonary cap to alveoli
ALVEOLAR PCO2
  • Air composed of 0.038% CO2 ∴FiO2 should be 0

Atmosphere

  • Negligible CO2 in atmosphere
  • ∴Removed from alveolus by ventilation & expired into atmosphere