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Smoke reaches the air sacs

Inhaled smoke travels down the airways to tiny air sacs in the lungs. There, carbon monoxide slips into the blood and takes the place on red blood cells where oxygen normally attaches.

In the picture

  1. Gray smoke particles inside an air sac
  2. Thin air sac wall where gases pass into the blood
  3. Carbon monoxide molecule attached to a red blood cell
  4. Oxygen molecule left outside the capillary

Examples

  • Cigarette smoke breathed into the lungs
  • A car engine releasing carbon monoxide in exhaust

Quiz: Smoke reaches the air sacs (Age 14)

  1. When smoke reaches the air sacs, what does carbon monoxide do?

    • It stays in the air sacs and is breathed out.
    • It takes the place on red blood cells where oxygen normally attaches.
    • It helps oxygen attach to red blood cells more easily.
  2. How does carbon monoxide compare with oxygen when binding to red blood cells?

    • It binds about the same as oxygen does.
    • It binds much more strongly than oxygen does.
    • It binds much more weakly than oxygen does.
  3. What can happen when the blood carries less oxygen?

    • The air sacs become larger.
    • Carbon monoxide is turned into oxygen.
    • Organs and tissues can be starved of oxygen.

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Biology, Age 14