B9.4

• Define: Metabolic reactions


  Chemical reactions that occur within a living organism in order for it to maintain life.
• What is Metabolic rate?


  Rate in which chemical reaction occur within a living organsim.
• Define 6 Roles of liver (JUST STATE ROLES)

  1-Production of Bile

  2-Removal of lactic acid

  3-Detoxification

  4-Breaking down of red blood cells

  5-Storage of glucose

  6-Break down of excess amino acids
• Explain why the liver produces bile

  During digestion, the liver produces bile and releases it into the duodenum via the bile duct.This is to emulsify fats, giving lipase enzymes a larger surface area to work on. Also, it neutralises the stomach acid as bile is alkaline which provides digestive enzymes with their optimum pH.
• How is the liver involved in the removal of lactic acid?

  Lactic acid is a bi-product of anaerobic respiration which can cause oxygen debt and cause muscle cramps.

  Muscles send this acid to the liver where it is converted back to glucose.This glucose is then either respired or stored as glycogen.

  This requires oxygen and the extra oxygen we need is called oxygen debt.
• What does the liver have to do with Detoxification?

  The enzymes in the liver break down toxic substances such as alcohol and hydrogen peroxide.As a result some liver cells are killed however in many cases are able to regenerate .However, is the substances is abused long term, then permanent damage(cirrhosis)can occur.
• How does the liver break down Red Blood cells?


  Red blood cells contain iron within their haemoglobin and so the liver recovers and stores it for the body to use.
• Does the liver store glucose?


  Yes.Excess glucose is removed form the blood via the liver and converts it into glycogen.

  When in demand, the liver breaks down the glycogen back into glucose for it to be returned to the blood.

  This is controlled by hormones.
• How are excess amino acids broken down?

  Amino acids can be used to make protein. However, the body cannot store it in excess. Therefore, they are broken by the liver via the process of deamination.This produces the toxin urea which enters the blood stream.Then, the kidney removes the urea and excretes it via urine.