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Topic 4 of 8 · Form 3

Human nutrition, transport and gas exchange

Balanced diet; deficiency diseases (scurvy, rickets, kwashiorkor); the alimentary canal; mechanical and chemical digestion; enzymes (amylase, protease, lipase); bile emulsifies fats; hydrochloric acid kills microbes and gives the optimum pH for pepsin; absorption in the small intestine via villi; water absorption in the colon.

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  1. PDFHuman nutrition, transport and gas exchange – Biology notes (Cambridge O Level)45.4 KB

Diet and digestion

Balanced diet; deficiency diseases (scurvy, rickets, kwashiorkor); the alimentary canal; mechanical and chemical digestion; enzymes (amylase, protease, lipase); bile emulsifies fats; hydrochloric acid kills microbes and gives the optimum pH for pepsin; absorption in the small intestine via villi; water absorption in the colon.

The circulatory system

Double circulation; the heart (chambers, valves, coronary arteries); coronary heart disease risk factors (diet, smoking, stress, lack of exercise); blood vessels (arteries, veins, capillaries); blood components (red cells, white cells, platelets, plasma).

Gas exchange

Features of gas exchange surfaces (large surface area, thin, good blood supply, ventilation); breathing mechanism; composition of inspired and expired air; effects of exercise on breathing; effects of tobacco smoke (tar, nicotine, carbon monoxide).

Respiration

  • Aerobic: glucose + oxygen → carbon dioxide + water (releases much energy).
  • Anaerobic in muscles: glucose → lactic acid (oxygen debt).
  • Anaerobic in yeast: glucose → ethanol + carbon dioxide (bread and brewing).
Exam tip: Explain how each feature of the alveoli increases the rate of diffusion.

Check yourself

  1. Name the blood vessel that carries blood from the heart to the lungs.
  2. Why does the heart rate increase during exercise?
  3. What is the role of bile?
Show answers
  1. The pulmonary artery.
  2. To deliver more oxygen and glucose to muscles and remove carbon dioxide faster.
  3. It emulsifies fats into small droplets, increasing the surface area for lipase.
Next topicDiseases and immunity

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