Liver function

• Storage of glycogen

  Liver stores sugars in form of glycogen. Glycogen forms granules in cytoplasm of hepatocytes. Glycogen can be broken down to release glucose into blood as required.
• Catalase (detoxification)


  Converts hydrogen peroxide to oxygen and water.
• Cytochrome P450 (detoxification)


  Group of enzymes used to breakdown drugs including cochineal and various medicinal drugs. Their role in metabolising drugs can interfere with other metabolic roles and cause unwanted side effects of some medicinal drugs
• Detoxification of alcohol 1

  • Alcohol broken down in hepatocytes by action of enzyme ethanol dehydrogenase. Resulting compound is ethanal.
  • This is dehydrogenated further by enzyme ethanal dehydrogenase.
  • Final compound produced is ethanoate (acetate). This acetate combined with coenzyme A to form acetyl coenzyme A. Hydrogen atoms released from alcohol combined with another enzyme (NAD) to form reduced NAD.
• Detoxification of alcohol 2

  • NAD also required to oxidise and breakdown fatty acids for use in respiration.
  • If the liver has to detoxify too much alcohol, it uses up stores of NAD and has insufficient left to deal with fatty acids.
  • Fatty acids converted back to lipids and stored as fat in hepatocytes causing liver to enlarge. Condition known as 'fatty liver'
• Formation of urea 


  Excess amino acids cannot be stored (need 40-60g of protein each day) amino groups make them toxic. Amino acid molecules contain a lot of energy so it would be wasteful to excrete the whole molecule. Excess amino acids undergo treatment in liver to remove and excrete amino component.treatment consists of two processes: d3amination followed by ornithine cycle.
• Formation of urea

  
• Deamination 


  Process of deamination removes amino group and produces ammonia. Ammonia is very soluble and highly toxic. Ammonia mustn't be allowed to accumulate. Deamination also produces an organic compound. A keto acid.
• Deamination

  
• ornithine cycle 1


  because ammonia is very soluble and toxic, must be converted to less toxic form very quickly. ammonia is combined with carbon dioxide to produce urea. this occurs in ornithine cycle. ammonia and carbon dioxide combine with amino acid ornithine to produce citrulline. this is converted to arginine by addition of further ammonia. arginine is re-converted to ornithine by removal of urea
• ornithine cycle 2


  urea is both less soluble and toxic than ammonia. can be passed back into blood and transported around the body to kidneys. in kidneys urea is filtered out of blood and concentrated in urine. urine safely stored in bladder until its released from the body.
• ornithine cycle