CO2 Transport Mnemonic for USMLE

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Topic Anchor: CO2 Transport
- Gaseous CO2 in RBCs is converted into carbonic acid and bicarbonate to allow water-soluble transport in blood
  - CO2 + H2O <--> H2CO3 <--> HCO3— + H+
  - CO2 mainly carried as bicarbonate ion in blood
  - Catalyzed by carbonic anhydrase
  - pCO2 drives CO2 transport
    - In tissues
      - High pCO2 generated by respiration of tissues
        drives reaction forward
      - Conversion of CO2 → bicarbonate
        Bicarbonate diffuses into plasma, allowing reaction to continue
    - In lungs
      - Low pCO2 due to exhalation
        drives the reaction backward
      - Conversion of bicarbonate → CO2
        Bicarbonate diffuses from plasma into RBC to supply this reaction
- Used to buffer pH of blood
  - When blood is too acidic, reverse reaction is favored to increase pH
  - When blood is too basic, forward reaction is favored to decrease pH