Flashcards in F214:02:03 Functions of the Liver Deck (43):
Describe the functions of the liver
Control of: blood glucose levels, amino acid levels, lipid levels
Synthesis of: RBC in the fetus, bile, plasma proteins, cholesterol
Storage of: Vitamin A, D, B12, iron, glycogen
detoxification of: alcohol and drugs
break down of hormones
destruction of RBC
What does the liver control?
blood glucose levels, amino acid levels, lipid levels
What does the liver synthesise?
RBC in the fetus, bile, plasma proteins, cholesterol
What does the liver store?
Vitamin A, D, B12, iron, glycogen
What does the liver detoxify?
alcohol and drugs
What does the liver break down?
What does the liver destroy?
What is urea?
an excretory product formed from the break down of excess amino acids
What is the ornithine cycle?
the process in which ammonia is converted into urea.
Occurs partly in the cytosol and partly in the mitochondria
ATP is used
Where does the ornithine cycle take place?
partly in the cytosol and partly in the mitochondria
How much protein do we need per day?
Why cant amino acids be stored?
as the amine groups make them toxic
Why do we not simply excrete excess amino acids?
As they contain a lot of energy so it would be wasteful to do so.
What are the two stages of the break down of amino acids?
What is the equation for deamination?
amino acid -> ammonia + keto acid
Describe the products of deamination
produces ammonia, a very soluble and highly toxic compound
Also produces a keto acid, which can be directly respired to release energy
What other molecule is required for deamination?
Why must ammonia be turned into urea very quickly?
As it is so soluble and toxic
Describe the ornithine cycle
Ammonia (NH3) joins with CO2 to form Citrulline, H2O is lost
Ammonia bonds with CO2 again to form Arginine, H2O is lost
Arginine joins with H20 to form Urea
3 main stages of the ornithine cycle
What is the summarised equation of the ornithine cycle?
Ammonia + carbon dioxide -> urea + water
What is the symbol equation of the ornithine cycle?
2NH3 + CO2 -> CO(NH2)2 + H2O
Give an example of a compound that is produced in the body, which is detoxified by the liver
Name 4 techniques of rendering toxins harmless
combination with another molecule
What is catalase?
an enzyme which turns hydrogen peroxide to oxygen and water
What is the turn over number for catalase?
What is a turn over number?
The number of molecules 1 enzyme can catalyse in one minute
What is ethanol?
An alcohol, and drug that depresses the nerve activity
It contains chemical potential energy that can be used for respiration
How is alcohol broken down?
By the enzyme ethanol dehydrogenase, and produces ethanal, which is then reduced again by ethanal dehydrogenase to produce ethanoate- which combines with coenzyme A to form acetyl coenzyme A, which enters the process of respiration
What is another name for ethanoate?
Show the stages of breakdown of alcohol summarised
ethanol -> Ethanal + 2H -> Ethanoic acid -> acetyl coenzyme A -> to respiration
What happens to the 2H released from the break down of alcohol?
What happens if the liver has to detoxify too much alcohol?
Then less NAD can be used to oxidise and break down fatty acids, so these fatty acids then get converted back into lipids and then are stored in hepatocytes, causing the liver to become enlarged.
What is 'fatty liver'?
The condition whereby fatty acids get converted back into lipids and then are stored in hepatocytes, causing the liver to become enlarged.
What can 'fatty liver'? lead to?
alcohol related hepatitis or to cirrhosis
What are cytochrome P450 enzymes?
Enzymes in the liver responsible for the breakdown of some toxic molecules like cocain
Where is cytochrome P450 most concentrated?
In the endoplasmic reticulum of liver cells
Why are enzymes more effective in some enzymes than others?
How does this affect individuals?
Due to variation
As it means that drugs can be more effective in some than others, and may cause variable side effects
What is detoxification?
the conversion of toxic molecules into less or non toxic molecules
Suggest why P450s are most concentrated in the endoplasmic reticulum of the liver?
The P450s are proteins; these are manufactured by the ribosomes that are attached to the ER
so from here they can be packaged away in vesicles to be transported where they are needed
Suggest when medicinal drugs have different side affects in different people
Each person may have slightly different enzymes, so these may break down drugs in slightly different ways, producing slightly different byproducts
Explain why P450s are not identical in every person
Genetic variation means that different people have different alleles- which will produce slightly different enzymes