What is excretion?
Reveal answer
Removal of waste products of metabolism from the body.
Key words: metabolism
3(i) EXCRETION · RECALL
3.21 Excretory products of the lungs, kidneys and skin
18 recall questions. Answer from memory, reveal the answer, then rate yourself. Ratings stay on this device.
Ratings are saved in this browser on this device, under a KS4 key kept separate from International A Level recall. Written answers are temporary and cleared when you leave the page. Use Reset to clear the ratings on this device.
Which organ excretes carbon dioxide?
Reveal answer
The lungs.
Key words: lungs
Which organ excretes urea in urine?
Reveal answer
The kidneys.
Key words: kidneys
What does the skin excrete?
Reveal answer
Water, salts and a little urea in sweat.
Key words: sweat
Where is urea made?
Reveal answer
In the liver.
Key words: liver
How is urea formed?
Reveal answer
Excess amino acids → deaminated in liver → urea → blood → kidneys.
Key words: amino acids · liver
What is the removal of undigested food called?
Reveal answer
Egestion (not excretion).
Key words: egestion
Why must CO₂ be excreted?
Reveal answer
Forms acid in blood → pH falls → enzymes affected.
Key words: acid · enzymes
Why must urea be excreted?
Reveal answer
Urea is toxic → damages cells at high concentration.
Key words: toxic
Why does a high-protein diet give more urea?
Reveal answer
More excess amino acids → more deamination → more urea.
Key words: amino acids
What is meant by the term deamination?
Reveal answer
Removal of the amino group from excess amino acids in the liver.
Key words: deamination
Human excretory organs: for Lungs, give the main excretory products and the route.
Reveal answer
Main excretory products: Carbon dioxide and water vapour. Route: Exhaled air.
Key words: Lungs
Human excretory organs: for Kidneys, give the main excretory products and the route.
Reveal answer
Main excretory products: Urea, excess water and ions. Route: Urine.
Key words: Kidneys
Human excretory organs: for Skin, give the main excretory products and the route.
Reveal answer
Main excretory products: Water, ions and a little urea. Route: Sweat.
Key words: Skin
Human excretory organs: for Liver, give the main excretory products and the route.
Reveal answer
Main excretory products: Makes urea and detoxifies substances. Route: Products enter blood for kidney removal.
Key words: Liver
True or false, and why? “Faeces are an excretory product.”
Reveal answer
False. Most faecal material was never absorbed; its removal is egestion.
True or false, and why? “Kidneys make urea.”
Reveal answer
False. The liver makes urea; kidneys remove it from blood.
True or false, and why? “Sweating is mainly for removing urea.”
Reveal answer
False. Its main role is thermoregulation; only a small amount of urea is lost.