Liver Flashcards
The Liver
Over 500 functions..mostly involved in homeostasis
Metabolism of carbohydrates lipids and proteins
Absorbed nutrients are carried to liver from gut by the hepatic portal vein
How is it involved in Glycogen storage
Carbohydrates
Excess converted into glycogen under the influence of the hormone insulin this is stored in liver and muscle cells
Lipids
Forms lipoproteins Excess carbohydrate and protein can be converted into triglyceride, this along with lipid that is not oxidised in the liver, is converted by the liver into low density lipoprotein Stores fats Synthesises cholesterol Forms bile salts from cholesterol Converts glucose to fats Converts fats to fatty acids and glycerol Converts fats/glycerol to glucose
Transamination
Amino acids may be converted from one form to another by transamination
Transfer of an amine group from an amino acid to an organic acid
Amino acids in diet may not match body’s requirements
Can convert a type of amino acid in excess to one in short supply.
Deamination
Excess amino acids are modified (by removal of the amino group NH2) and the residue is respired or converted into fats
This deamination forms (highly toxic) ammonia
Converted to urea by addition of carbon dioxide
Transferred to kidneys to be excreted
Deamination
Ammonia is produced which is soluble and toxic
Keto acid is produced which enters respiration directly to release energy
Detoxification
Many dangerous substances are broken down by the liver
Some are made harmless, some are excreted into bile
Most of these processes take place in the smooth endoplasmic reticulum in the hepatocytes
Toxins can be made harmless by oxidation, reduction, methylation or combination with another molecule
Detoxification of alcohol
Depressant – depresses nerve activity
Chemical potential energy which can be used for respiration
ethanOL to ethanAL by ethanol dehydogenase enzyme
Ethanal to ethanoic acid by ethanal dehydogenase enzyme
Acetate is final product
Explain what happens to Hs in detoxification of alcohol
The Hydrogen atoms released are combined with another coenzyme called NAD to form reduced NAD
NAD is also needed to oxidise and break down fatty acids for respiration
If the liver has to detoxify too much alcohol, it does not have enough NAD to deal with the fatty acids, so they are changed back to lipids and are stored in hepatocytes (liver cells), causing the liver to become enlarged- this is called ‘fatty liver’ and can lead to liver cirrhosis.
Detoxification
The liver is responsible for the breakdown of many drugs and poisons
Hydrogen peroxide
Ethanol is converted first into acetaldehyde which is then metabolised (too much alcohol kills liver cells)
Lactate Removal
Lactate which can be damaging to muscles can be transported to the liver where it can be converted
Glucose and metabolised
Or stored as glycogen
Heat Generation
Metabolic rate and considerable energy production make the liver the main heat producing organ in the body. Under control of thyroxine.
Storage of minerals and vitamins
IRON –
-Kuppfer cell –specialised macrophage removes and breaks down old red blood cells.
Haemoglobin broken down into heam and globin. Iron removed from heam. Bilirubin formed.
Iron is stored as ferritin
Remainder passes to liver cells to form bile pigments. Globin broken down into amino acids.
-Fat soluble vitamins A, D, E, B12
Bile production
Produced by hepatocytes (liver cells)
Manufactures bile continuously
Carried out of liver via bile ducts
Excess bile flows into gall bladder where it’s stored for further u
Structure of the Liver – Histology
Best possible contact between blood and liver cells
The liver tissue is arranged into numerous roughly cylindrical lobules, each about 1mm in diameter
Blood is supplied to each lobule by smaller and smaller branches of the hepatic artery and the hepatic portal vein (inter-lobular vessels)
Blood exits via the hepatic vein
