CIE IGCSE Biology

Revision Notes

13.1.1 Excretion in Humans

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Excretion of Carbon Dioxide & Urea

  • Unlike plants, humans have organs which are specialised for the removal of certain excretory products
  • They include the lungs and kidneys
  • The liver also has a vital role in excretion

 

Organs involved in excretion, IGCSE & GCSE Chemistry revision notesOrgans involved in excretion

 

The Excretory System table, IGCSE & GCSE Biology revision notes

  • Excretion is the removal of the waste substances of metabolic reactions (the chemical reactions that take place inside cells), toxic materials and substances in excess of requirements
  • Carbon dioxide must be excreted as it dissolves in water easily to form an acidic solution which can lower the pH of cells
  • This can reduce the activity of enzymes in the body which are essential for controlling the rate of metabolic reactions
  • For this reason, too much carbon dioxide in the body is toxic
  • Urea is also toxic to the body in higher concentrations and so must be excreted

The urinary system in humans, IGCSE & GCSE Chemistry revision notes

The urinary system in humans

 Main structures involved:The Urinary System table, IGCSE & GCSE Biology revision notes 

Exam Tip

Note the difference between the ‘ureter’ and the ‘urethra’. These two names are commonly confused by students so take care to learn them and know which tube is which – they are NOT interchangeable!

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Author: Lára

Lára graduated from Oxford University in Biological Sciences and has now been a science tutor working in the UK for several years. Lára has a particular interest in the area of infectious disease and epidemiology, and enjoys creating original educational materials that develop confidence and facilitate learning.