Excretion

Excretion

  • the biological process of removing waste products from the body

  • includes substances produced during metabolism

  • crucial for maintaining internal balance

  • prevents the accumulation of harmful materials in bodily systems

Egestion

  • the biological process of expelling undigested food material from the body as faeces through the anus

Formation of Urea

  • deamination

    • excess amino acids are broken down in the liver

    • amino group is removed to produce ammonia

  • ornithine cycle

    • ammonia is converted into less toxic urea

    • requires ATP

The ornithine cycle

  • ammonia from deamination is combined with carbon dioxide to form urea and water

  • urea is less toxic and less soluble than ammonia making it safer for transport and excretion

  • urea is then transported to the kidneys and excreted in urine

  • ornithine cycle

Removal of carbon dioxide

  • carbon dioxide dissolves in blood plasma forming carbonic acid and hydrogen ions thus lowering pH

  • hydrogen ions can bind to haemoglobin, reducing oxygen transport and forming carbaminohaemoglobin

  • excess CO2 can lead to respiratory acidosis, causing symptoms like drowsiness, confusion, and rapid heart rate

    • (H+ ions lower pH so blood is acidic)