Chapter 30 Flashcards
how are amino acids obtained from the diet?
when proteins are digested
why are cellular proteins degraded to amino acids?
because of damage or for regulatory purposes
what is the first priority for use of amino acids?
as a precursor for proteins or other biomolecules
can muscles use amino acids as an energy source?
yes, under certain conditions
what happens when there is an excess of amino acids?
amino acids are not stored, so any excess amino acids are degraded
amino acids can be converted to intermediates in the ____ cycle with NH3
how are alpha-amino groups converted into ammonium ions?
by oxidative deamination of glutamate
how is nitrogen transported to the liver?
by peripheral tissues
specifically the glucose-alanine cycle
how do muscles use branched-chain amino acids?
as fuels during prolonged exercise and fasting
what is the glucose-alanine cycle?
the nitrogen removed from the amino acid is transferred (through glutamate) to alanine, which is released into the bloodstream
In the liver, alanine is taken up and converted into pyruvate for the subsequent synthesis of glucose
largely used by muscles to remove ammonia from amino acids
what is the urea cycle?
excess NH4+ is converted into urea
what are ureotelic organisms?
organisms that excrete excess NH4+ as urea
where does the urea cycle occur?
in the liver
how are amino acids transferred?
as free ammonia or aspartate
what do defects in urea cycle enzymes cause?
elevated levels of NH4+ in the blood
this causes nervous system malfunction and can be lethal
why can liver damage caused y excessive alcohol consumption be fatal?
because the liver is unable to synthesize urea and consequently NH4+ appears in the blood
what can happen do to excessive alcohol consumption?
fatty liver develops - ⇑ NADH
Alcoholic hepatitis - inflammation of liver, cell death, ⇑ acetaldehyde
Cirrhosis - fibrous, scarring of tissue, ⇑ NH4+ (liver is destroyed)
what reversible issue can excessive alcohol consumption cause?
alcoholic hepatitis
what is an irreversible result of excessive alcohol consumption?
cirrhosis
what are the intermediates that carbon skeletons of amino acids are metabolized to?
- pyruvate
- acetyl CoA
- acetoacetyl CoA
- alpha - ketoglutarate
- succinyl CoA
- fumarate
- oxaloacetate
what are ketogenic amino acids? why are they called this?
amino acids metabolized to acetyl CoA and acetoacetyl CoA
because they can produce Acetyl CoA for the CAC and also form fats but not glucose
can create ketone bodies
what amino acids are solely ketogenic?
Leucine and Lysine
what are glucogenic amino acids? why?
amino acids degraded to the remaining major intermediates (pyruvate, alpha-ketoglutarate, succinyl CoA, fumarate, and oxaloacetate)
because they can be used to synthesize glucose
amino acid ⇒ phosphoenolpyruvate ⇒ glucose
can ketogenic amino acids go back to produce glucose?
NO
