29 下列那一個胺基酸可以降解成fumarate？

Phenylalanine Alanine Cysteine Serine

BONUS

TYROSINE

ASPARTATE

PHENYLALANINE

REVIEW THE UREA CYCLE:

The urea cycle (also known as the ornithine cycle) is a cycle of biochemical reactions occurring in many animals that produces urea ((NH₂)₂CO) fromammonia (NH₃)

Organisms that cannot easily and quickly remove ammonia usually have to convert it to some other substance, like urea or uric acid, which are much less toxic. Insufficiency of the urea cycle occurs in some genetic disorders (inborn errors of metabolism), and in liver failure. The result of liver failure is accumulation of nitrogenous waste, mainly ammonia, which leads to hepatic encephalopathy

Reactions

The urea cycle consists of five reactions: two mitochondrial and three cytosolic.

Reactions of the urea cycle

Step	Reactants	Products	Catalyzed by	Location
1	NH4+ + HCO3− + 2ATP	carbamoyl phosphate + 2ADP + Pi	CPS1	mitochondria
2	carbamoyl phosphate + ornithine	citrulline + Pi	OTC	mitochondria
3	citrulline + aspartate + ATP	argininosuccinate + AMP + PPi	ASS	cytosol
4	argininosuccinate	Arg + fumarate	ASL	cytosol
5	Arg + H2O	ornithine + urea	ARG1	cytosol