metabolism 4.2.3

• metabolism is the sum of all the chemical reactions that take place in a cell or in a body
• examples of metabolic reactions include:

  • cell division
  • photosynthesis
  • respiration
  • active transport
  • enzyme reactions
  • breakdown of toxic products
  • bile production
• Metabolism includes:

  • conversion of glucose to starch, glycogen and cellulose

  • the formation of lipid molecules from a molecule of glycerol and three molecules of fatty acids

  • the use of glucose and nitrate ions to form amino acids which in turn are used to synthesise proteins

  • respiration

  • breakdown of excess proteins to form urea for excretion.
• The energy transferred by respiration in cells is used by the organism for the continual enzyme controlled processes of metabolism that synthesise new molecules.
• the liver is a very active organ with many different metabolic functions
• a liver cell would have lots of mitochondria because it is very metabolically active
• the functions of the liver include:

  • detoxifying poisonous substances such as ethanol
  • passing the breakdown products into the blood so they can be excreted in the urine via the kidneys
  • breaking down the old work out blood cells and storing iron until it is needed to make more blood cells
  • making bile
  • converting lactic acid into glucose