Chapter 12 - Excretion

?
  • Created by: E456
  • Created on: 17-03-17 12:14

EXCRETORY PRODUCTS

  • excretion= the removal from organisms of the waste products of metabolism (chemical reactions in cells including respiration), toxic materials, and substances in excess of requirements. 
  • Cellulose is not an excretory product because it has never been used in any metabolic reaction in a person's cells. The process of getting rid of undigested cellulose in faeces in called egestion

NITROGENOUS WASTE

  • nitrogenous waste= waste formed from excess proteins and amino acid; animals produce this kind of waste.
  • urea= it is formed in the liver and is a toxi substance; also, it is removed from the body by the kidneys.
  • deamination= the removal of the nitrogen-containing part of aminao acids to form urea. 
  • Enzymes in the liver split up each amino acid molecule. The part containing the energy is kept and turned into carbohydrate and stored. The rest, which contains nitrogen, is turned into urea. 
  • Functions of the liver:
    • converts excess amino acids into urea and carbohydrates (deamination).
    • synthesises plasma proteins such as fibrinogen, from amino acids. 
    • controls the amount of glucose in the blood, with the aid of the hormones insulin and glucagon. 
    • stores carbohydrate as the polysaccharide glycogen.
    • makes bile.
    • breaks down old red blood cells, storing the iron and excreting the remains of the haemoglobin as bile pigments.
    • breaks…

Comments

No comments have yet been made