Urea Cycle Flashcards
The urea cycle is connected to the TCA cycle by which process?
Asp and Arg shunted into TCA as oxaloacetate
arginino-succinate breaks into arginine and fumerate by aspartate aminotransferase
What goes in and out of the Urea cycle?
Carbamoyl phosphate (built from bicarbonate and NH3+)
Eventual formation of arginine and fumerate
Arginine -> hydrolysis to urea and ornithine (orn is recycled)
Fumerate into the TCA cycle and out into gluconeogenesis
What is responcible for the digestion of proteins in the stomach?
Pepsin
What is ubiquitin’s purpose, in general, in a cell?
Ubiquitin covalently tags protiens/targets for degration in the proteosome. (4 ubiquitin)
The ubiquitin bound to the protein finds the 19s regulatory units of the proteosome and active the structure, it tells the proteosome that its services are needed.
What are the basic stages of amino acid metabolism?
Amino Acid -> a cylce between glutamate and a-ketogluterate. Reduction of NAD+ and release of ammonium
Ammonium can go on to many processes but mainly excreted as urea
This reaction is driven forward by ^^^^ removal of NH4+
Ammonium is damaging to tissues and cannot be released into the bloodstream as is, how is it released from cells?
Alanine and Glutamine
-from muscle
What’s the clinical purpose of aminotransferases ALT and AST? What’s their coenzyme?
Alanin transaminase and Aspartate transaminase are markers for liver damage, these are screened for in hepatic panels.
Vitamin b6 derivites pyridoxyl-5-phosphate is the coenzyme for aminotransferases
The urea cycle builds corbomoyl phosphate from what and with which enzyme?
Irreversible reaction in the mitochondria. Take ammonium and builds carbamoyl phosphate with carbamoyl phosphate synthetase.
Rate limiting
Pos stim: NAG
Requires 2 ATP’s
What is the fate of ammonium?
- Formation of car amply phosphate
- Reaction with ornithischians to make citrulline which transports to the cytosol
- Condense to make argininosuccinate
- Cleaved: arginine and fumerate
- Arginine hydrolyzed to urea and ornithine
What connects the urea cycle and gluconeogenesis?
Argininosuccinate,
Arginine goes on in the urea cycle
Fumerate goes off into gluconeogensis to form Oxaloacetate and glucose
Which amino acids can become either ketogenic or glucogenic molecules?
Isoleucine Tryptophan Phenylalanine Tyrosine Threonine
Iso, thr. Not converted to acetylacetate, but to Acetyl coa
All other switch hitters become acetolacetate
MSUD
A inborn error of metabolism
Deficient dehydrogenase complex
Causes a build up of branched chain amino acids
What is PKU?
An inborn error of metabolism
Phenylalanine dehydrogenase is absent or missing (Phe ->/ Tyr (Try->acetoacetate and fumerate))
“Phenylketonuric”
If untreated -> severe mental retardation.
What amino acids are ketose if? What does that mean they can become?
Leu and Lys
Acetyl-CoA and Acetoacteate
