Excretion + Urea Formation Flashcards
why do waste products damage the cells?
they are toxic
what is excretion?
the removal of toxic waste substances which have been made by cells
what is egestion?
the removal of faeces by the body
what does faeces consist of?
consists of undigested food which has passed through the alimentary canal without entering cells
where does respiration occur?
in all living organisms in the mitochondria of cells
what is a waste product from respiration and how is it removed?
- carbon dioxide
- removed via the lungs in animals and through leaves in plants
why do amino acids need to be removed from the body?
what they are broken down into is toxic and therefore must be removed from the body
where is carbon dioxide made and how?
- made in respiring cells
- through respiration
where is carbon dioxide removed?
lungs via blood plasma
where is urea made and how?
- liver cells
- breakdown of amino acids (deamination)
where is urea made?
kidneys and skin
what is the process of urea formation?
- amino acids are filtered into the liver, along with the rest of the blood via the hepatic artery and hepatic portal vein
- excess amino acids cannot be stored and need to be broken down so they can be excreted - they are broken down into carbohydrates and ammonia
- ammonia is very toxic and must be converted into a slightly less toxic chemical called urea
- amino acids that are need and the urea are released back into the blood stream via the hepatic vein
