Human Biology 4HB1/02 November 2020 | Edexcel IGCSE Past Papers With Mark Scheme

Edexcel International GCSE Human Biology (4HB1) Nov 2020

معلم موافق رایگان بودن است.

1. Disease transmission and immunity: malaria–protoctist via mosquito, polio–virus via contaminated water, typhoid–bacterium via food/water, athlete’s foot caused by fungus not bacteria, antibiotics ineffective

2. Lipid digestion experiment: lipase enzyme, phenolphthalein pH indicator, bile salts increase surface area for faster digestion, sodium hydrogencarbonate raises pH, tube C as denatured enzyme control

3. Alveolar gas exchange: red blood cells transport O₂, alveolar air has less O₂ and more CO₂ than atmospheric air, adaptations include large surface area, thin walls, close capillaries; emphysema reduces elastic recoil, impairs ventilation

4. Aspirin dissolution test: sucrose speeds up acidity (lower pH faster), starch delays release, dependent variable is pH change over time, controlled variables include temperature and water volume, improved formulation enables faster pain relief

5. Hearing mechanism: ossicles (P, Q, R) transmit vibrations from eardrum to inner ear, structure S (pinna) channels sound, fluid-filled medium for wave transmission, cochlea and auditory nerve not shown

6. Alcohol and urine output: alcohol suppresses ADH release from pituitary (endocrine system), increases urine production, dehydration thickens blood, reduces plasma volume, rehydration inefficient due to 50% water retention rate