Protein synthesis and the urea cycle in liver disease Flashcards
Amino acids split into
alpha-Keto acids and NH4+
Where does the alpha-keto alpha acids go and used in?
Go to citric acid cycle for respiration
Where is the enzyme alanine amino-transferase found?
Muscle and liver.
High levels of ALT may be a sign of liver damage from hepatitis, infection, cirrhosis, liver cancer, or other liver diseases
Why is the liver important in protein break down?
Stores more proteins than other tissues
Can rapidly synthesis or degrade proteins
Unlike other tissues, can also rapidly synthesise or degrade amino acids.
How many amino acids can be made in the body and how many are essential in the diet?
10 can be synthesised, 10 have to be taken in
How does transamination work (making amino acids?)
1) Precursor alpha-keto acid needed (eg. pyruvate)
2) Donor of amino group needed (commonly glutamic acid)
3) An aminotransferase enzyme catalyses reaction (like alanine transaminase or aspartate transaminase)
What promotes protein synthesis
Insulin and growth hormone
When there is tissue amino acid deficiency, where can amino acids be found?
The plasma proteins in the blood can be broken down.
Note that plasma proteins maintain oncotic pressure in blood as they hold water in the plasma
Liver disease can often lead to bleeding because…
Fewer clotting factors made from liver.
Vitamin K is fat-soluble and essential for the carboxylase enzyme needed to make clotting factors. What is needed for its digestion and absorption and what condition might prohibit this?
Bile, biliary obstruction. May cause bleeding as not making clotting factors.
In transamination, amino acids are converted to keto acids. What else is produced?
Glutamate
How is ammonium formed?
The glutamate produced from transamination has the amine group taken off, catalysed by glutamate dehydrogenase to from ammonia, then forms ammonium.
Where does the urea cycle take place?
Cytoplasm and mitochondria of hepatocytes.
What happens in the mitochondria of hepatocytes?
Ammonia reacts with ATP and CO2 to form citrulline from ornithine.
