CIE A Level Biology (9700) 2019-2021

Revision Notes

9.2.2 The Effects of Nicotine & Carbon Monoxide

Nicotine & Carbon Monoxide Effects

  • Nicotine and carbon monoxide in cigarettes affect the ability of the cardiovascular system to function properly
  • Nicotine is the addictive component of cigarettes. It causes vasoconstriction, which is the narrowing of blood vessels
  • Vasoconstriction limits the flow of blood around the body, increases blood pressure and makes it harder for oxygen to reach all body cells
  • This lack of oxygen can force cells to respire anaerobically, creating lactic acid
  • Nicotine can also make platelets ‘sticky’ and they clump together, potentially forming a thrombosis (blood clot)

Carbon monoxide

  • Once inhaled, carbon monoxide in cigarettes binds to haemoglobin instead of oxygen
  • This is because chemically carbon monoxide has a much higher affinity for haemoglobin than oxygen
  • When this happens, oxygen cannot bind to haemoglobin and carboxyhaemoglobin (COHb) is formed instead of oxyhaemoglobin
  • This decreases the amount of oxygen delivered to cells for aerobic respiration and cells may have to respire anaerobically instead
  • This forces the heart to work harder to pump and deliver adequate oxygen, increasing heart rate and causing breathlessness
  • Carbon monoxide also promotes the release of free radicals, such as peroxides and superoxides
  • Carbon monoxide can also cause platelets and neutrophils to stick together, affecting the ability of white blood cells to fight infection

Worked example

The drug nicotine has a similar structure to acetylcholine. Suggest the effects on brain neurons of inhaling nicotine from a cigarette.

Nicotine will fit into membrane receptors and is not broken down by enzymes. This means that action potentials are generated for a long period of time.

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