Edexcel iGCSE Biology-2.49 Smoking & the Gas Exchange System- Study Notes- New Syllabus

Biological Consequences of Smoking

📝 Introduction

Cigarette smoke contains harmful substances like tar, nicotine, and carbon monoxide.
These chemicals damage the lungs and heart/blood vessels, leading to serious health problems.

🫁 Effects on the Lungs

• Tar
  Sticky black substance that coats lungs.
  Destroys cilia in airways → mucus is not cleared properly.
  Causes mucus build-up, coughing, and more infections (like bronchitis).
  Increases risk of lung cancer (carcinogenic).
• Chronic Bronchitis
  Inflammation of bronchi.
  Airways narrow, excess mucus forms → breathing becomes harder.
• Emphysema
  Alveoli walls break down and fuse → reduces surface area.
  Gas exchange efficiency drops → person feels breathless.

❤️ Effects on the Circulatory System

• Carbon Monoxide (CO)
  Combines with haemoglobin to form carboxyhaemoglobin.
  Reduces oxygen transport in blood → strain on heart.
• Nicotine
  Increases heart rate and blood pressure.
  Makes platelets sticky → risk of blood clots.
• Atherosclerosis (hardening of arteries)
  Fatty deposits build up inside arteries → arteries become narrower.
  Reduces blood flow → increases blood pressure.
• Coronary Heart Disease (CHD)
  Caused by blocked coronary arteries (supplying the heart muscle).
  Heart muscle gets less oxygen → risk of heart attack.

📊 Summary Table

⚡ Quick Recap
Tar → cancer, cilia damage, bronchitis.
Nicotine → addiction, ↑ heart rate & clotting.
CO → less O₂ transport.
Lungs → bronchitis, emphysema, cancer.
Circulatory system → atherosclerosis, CHD, strokes, heart attacks.