Error 1 — RV vs FRC Confusion Many students write: "RV is the air after normal expiration." This is WRONG. FRC (= ERV + RV) is the air after normal expiration. RV is the air after MAXIMUM FORCED expiration. RV < FRC always.

Error 2 — VC includes RV A very common error: VC = TV + IRV + ERV + RV. Correct: VC = TV + IRV + ERV. RV is excluded because it cannot be voluntarily expelled. TLC = VC + RV.

Error 3 — CO2 primary form = carbaminohaemoglobin Students who remember "CO2 binds haemoglobin" often select carbaminohaemoglobin as the dominant form. Correct: 70% is HCO3–; 23% is carbaminohaemoglobin; 7% is dissolved.

Error 4 — Quiet expiration is active Students assume all breathing phases require muscle work. Correct: quiet expiration is entirely passive (elastic recoil only). Only FORCED expiration is active.

Error 5 — Right shift = more O2 retained A conceptual reversal error. Right shift = LOWER O2 affinity = MORE O2 RELEASED to tissues. Haemoglobin "loosens its grip" when the curve shifts right.

Error 6 — CO2 binds haem iron CO2 binds to the amino (–NH2) groups of the GLOBIN protein chains, NOT to the haem iron where O2 binds. Confusing the binding sites is a common error.

Error 7 — Pneumotaxic centre initiates breathing The pneumotaxic centre LIMITS (inhibits) inspiration. The MEDULLARY RHYTHMICITY CENTRE initiates breathing rhythm.

Error 8 — Chloride moves out during the chloride shift The direction: HCO3– moves OUT of RBCs; Cl– moves INTO RBCs. Not the other way around.

Error 9 — Both lungs have 3 lobes Right = 3 lobes; Left = 2 lobes (cardiac notch).

Error 10 — Alveoli have 2 diffusion layers There are 3 layers: alveolar epithelium, basement membrane (shared), capillary endothelium. Not 2.