The liver.

• • Produces bile which helps break down fats (bile produced from ​

  Liver) bile is stored in gallbladder ​

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• Functions: ​

  • Stores vitamins and sugars until your body needs them​
  • Breaks down toxins so that they can be removed by the body​
• • The liver carries out several important roles in the body, including the breakdown of unwanted or toxic substances and the production of excretory waste​
  • In order to carry out these roles successfully, the liver requires a constant blood supply​
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• Metabolic Waste​

  • As mammals are active, warm-blooded animals, they have high metabolic rates, which means they also produce relatively large amounts of metabolic waste​
  • This metabolic waste includes:​
  • Carbon dioxide*​
  • Nitrogenous waste* (ammonia, urea and uric acid)​
  • Bile pigments (produced during the breakdown of haemoglobin)​
  • the liver is a key organ in producing all of these excretory substances (except for carbon dioxide)​
• Removal of Metabolic Waste​

  • Carbon dioxide is produced from the decarboxylation (removal of CO2 of respiratory substrates i.e. Glucose​​
  • Ammonia is produced from the deamination (removal of amino group) of excess amino acids​
  • If these two waste products are not excreted properly, they can accumulate and change the cytoplasm and body fluid pH​
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• Nitrogenous Waste – Ammonia, Urea and Uric Acid​

  • The main nitrogenous waste removed by humans is urea. ​
  • Urea is formed in the liver through deamination of excess amino acids. The amine group is removed creating ammonia which is toxic. Ammonia increases the pH of the cytoplasm affecting the activity of enzymes involved in metabolism. Ammonia also interferes with the receptors for neurotransmitters. ​
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• Nitrogenous Waste – Ammonia, Urea and Uric Acid​

  • Ammonia is converted into urea. If urea is not removed it diffuses into the cell lowering the water potential. ​
  • Uric acid is produced by the liver during the breakdown of guanine and adenine. If uric acid is not removed it can form crystals in the joints leading to gout. ​
• Control of Carbon Dioxide ​

  • arbon dioxide released as a waste product from respiring cells diffuses into the cytoplasm of red blood cells​
  • Inside red blood cells, carbon dioxide combines with water to form Carbonic Acid H2CO3   ​

  CO2 + H2O  ⇌  H2CO3​

  • Red blood cells contain the enzyme carbonic anhydrase which catalyses the reaction between carbon dioxide and water​
  • Carbonic acid breaks up into Hydro (H+) ions and bicarbonate ions (CO3-). ​
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  • An increase of carbon dioxide leads to an increase in H+ ions which increase blood acidity (increased pH) – What is the impact of increased pH?​
• If metabolic wastes are not removed how does this effect the body?​ Excretion is the process by which toxic waste products of metabolism and substances more than requirement are removed from the body.

  Excretion is a key process in homeostasis and is important in maintaining metabolism, as metabolic waste can have serious negative consequences on the body if allowed to accumulate.

  Waste products have to be processed and removed from the cells, as they can build up, poison, and eventually kill the cells.
• Acidosis is a condition in which there is too much acid in the body fluids.
• Carbon dioxide source the decarboxylation of respiratory substrates during aerobic respiration in mitochondria effects on the body cells damaged if blood pH falls below normal range (acidosis)
• Ammonia source the deamination of excess animo acids in liver cells effects on body increases cytoplasm pH and interferes with metabolic processes (respiration) and receptors for neurotransmitters in the brain.
• Urea source the ornithine cycle in liver cells effects on body if allowed to accumulate urea readily diffuses into cells. This decreases their water potential causing them to absorb water by osmosis and expand until they burst.
• Uric acid source the breaking down of adenine and guanine (i.e. purines) in the liver effects on body uric acid may form crystals in joints, causing gout (a very painful form of arthritis)
• Bile pigments source the breaking down of the haem groups of haemoglobin in liver cells effects on body bile pigments accumulate in skin turning it yellow (jaundice)