Nitrogen Metabolism Flashcards
Nitrogen balance
There is no long term storage for nitrogen except functional protein. Nitrogen balance = nitrogen input - nitrogen output.
Positive Nitrogen Balance
More nitrogen is entering the system than is leaving the system. This is common during times of physical growth.
Negative Nitrogen Balance
More nitrogen is leaving the system than is entering the system. Common during times of starvation and disease when protein is broken down so that the carbon skeletons can be used for energy.
Glutamate Dehydrogenase
In the liver, releases the second nitrogen. Converts glutamate to alpha ketoglutarate, releasing NH4+ that enters the urea cycle.
Glutamine Synthetase
Adds a nitrogen to glutamate, making glutamine, which can then exit the cell and take nitrogen to the liver, to be entered into the urea cycle.
Aminotransferase
Transfers the amino group of an amino acid to alpha ketoglutarate, making glutamate.
Glutaminase
In the liver, releases the first nitrogen from glutamine, producing glutamate. The nitrogen can then enter the urea cycle.
What are the four enzymes important for nitrogen transport?
In the cell: Aminotransferase and Glutamine Synthetase
In the liver: Glutaminase and Glutamate Dehydrogenase
What is the diagnostic significance of ALT and AST?
ALT (alanine aminotransferase) and AST (aspartate aminotransferase) are important enzymes in liver cells. In a healthy liver, they are contained within the cells. If there is evidence of AST and ALT in the blood, then this is evidence of damage to the liver.
What is the urea cycle and why is it important?
The urea cycle is a way for the body to safely get rid of nitrogen. It occurs in the liver and processes the nitrogen it receives from all over the body in the forms of glutamine and alanine. It requires and input of energy.
