The liver

The liver

1. Detoxification of alcohol

   • Takes place in the smooth endoplasmic reticulum of the Hepatocytes
   • Ethanol molecules are small and fat soluble so can pass through the phospholipid bilayer into cells.
   • 1. Ethanol is converted into ethanal by ethanol dehydrogenase.
   • 2. Ethanal is converted into ethanoic acid by ethanal dehydrogenase.
   • 3. Ethanoic acid in converted into Acetlycoenzyme A
   • Fatty liver---- NAD is required to oxidise fatty acids. If too much alcohol is consumed, there is not enough NAD to do so. As a result, fatty deposits build up in the liver.
   • Cirrhosis ----- Toxins in alcohol damage the hepatocytes. Damaged hepatocytes are replaces by fibrous tissue. The liver is not able to effectively carry out its function.

2. Blood supply

   • Receives oxygenated blood from the hepatic artery which branches off the Arota.
   • The hepatic portal vein carries blood from the digestive system so that the kidneys can control the levels of compounds ingested.
   • Blood is carried by the hepatic vein back to the vena cava

3. Functions

   • Control of blood glucose levels
   • synthesis of cholesterol and plasma proteins
   • Detoxification of alochol

4. Excretion

   • The removal of metabolic waste from the body. This is the unwanted substances produced in cell chemical reactions.
   • Excretion of CO2
     • Binds with haemoglobin to from carbaminohaemoglibin. This has a lower affinity for O2.
     • Dissolves in plasma and combines with H2O to form carbonic acid.
       • This dissociates into HCO3- and H+.
         • This increases the acidity of the blood.
           • Leads to breathing difficulty, headaches, drowsiness, tremors and confusion.
   • Excretion of Nitrogenous compounds
     • Amino acids cannot be stored so they are Deaminated in the liver. This produces ammonia which is highly toxic. It must be converted into urea.
     • The remaining Keto acids are respired or turned into a carbohydrate or lipid for storage.

5. The Ornitine cycle

   • 1. Ornitine + NH3 + CO2 ----> Citrulline + H2O
   • 2, Citrulline + NH3 -----> Arginine + H2O
   • 3. Arginine + H2O -----> Urea + Ornithine

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