8: Biochemistry - Amino acid catabolism Flashcards
Amino acids can be ___ to release energy.
oxidised
Do amino acids have a storage form in the body?
No - they can’t be stored
Which enzymes, found in the GI tract, digest proteins into amino acids?
Proteolytic enzymes
Which element is contained in the side chains of some amino acids?
Nitrogen
What is produced by the degradation of amino acids which contain nitrogen atoms?
Ammonia (NH3) and ammonium ions (NH4+)
Ammonium is ___ at high concentrations.
toxic
What is urea?
An excretory molecule which contains nitrogen
In which organ does amino acid degradation take place?
The liver
Where is urea produced?
The liver
What happens in the transamination step of urea synthesis?
Amino group transferred from amino acid to keto acid, giving glutamate
Which enzymes carry out the transamination step of urea synthesis?
Aminotransferases
What happens in the de-amination step of urea synthesis?
Amino group from glutamate converted into ammonium (NH4+)
What occurs in the urea cycle?
Conversion of ammonium to urea
Urea cycle
Transamination
De-amination
What is the correct order of steps in the synthesis of urea?
Transamination
De-amination
Urea cycle
Where do de-amination and the urea cycle occur?
Liver
Carbon skeletons left behind after the removal of amino groups during urea synthesis can then be oxidised in the ___ cycle.
TCA
Kreb’s cycle
Some carbon skeletons can also be used to synthesise glucose in ___.
gluconeogenesis
Failure in amino acid degradation can cause ___.
disease
What is phenylketonuria?
Failure to break down phenylalanine, which then accumulates and causes mental retardation
Which disease results from the failure to degrade, and subsequent accumulation of, phenylalanine?
Phenylketonuria
Defects in urea cycle enzymes may cause the accumulation of ammonium ions, which are ___.
toxic
