Flashcards in Nitrogen and AA Metabolism Deck (52):
where does Nitrogen come from?
diet - there is no storage form!
in what form is nitrogen released from the kidney ?
as ammonium ions
in what form is N released from the liver - major!?
urea from the urea cycle
what is the amino acid pool?
all the free amino acids in cells, blood and extracellular fluid.
Its the center of whole body N metabolism = 100 g of aa
what 3 things can fill the aa pool?
1. dietary amino acids
2. synthesized nonessential amino acids
3. amino acids generated by body protein degradation.
What are the aa in the aa pool taken out and used for?
1. for body protein synthesis
2. for synthesis of specialized products derived by conversion of amino acids
3. for eventual degradation for energy metabolism in all cells or for synthesis of glucose or ketone bodies in hepatocytes [glucogenic and ketogenic amino acids]
what is dietary essential in children?
what is semi-essential or conditionally non-essential in adults?
The deficiency of which amino acid makes tyrosine an essential amino acid?
The deficiency of which amino acid makes cysteine an essential amino acid?
Name three concepts how humans can synthesize non-essential amino acids.
1. aminotransferase rxns
2. amidation rnxs
3. other aa as precursors (cysteine+tyrosine)
what does ubiquitin use for energy?
what is lysosomal degradation independent of?
ATP - does not use!
what type of aa have a complex structure?
essential aa - can't make - aren't close to glycolysis or TCA cycle intermediates in terms of structure
what type of aa have a close structure to those of glycolysis or TCA cycle intermediates?
non-essential - body makes them
what food group has the most N?
How are dietary amino acids transported into the intestinal mucosal cells?
Amino acids during digestion are transported against a concentration gradient by secondary active co-transport with sodium ions into the intestinal mucosal cell
what happens if one of the aa transporters are deficient?
that transporter is deficient in the intestinal mucosal cell and in the kidney
leads to less up take of the respective group of aa into intestinal mucosal cells and leads to higher urinary levels than normal of aa as reuptake by the kidney is also deficient
how does the liver obtain most of the dietary aa?
where do the aa go that are not being used by the liver?
what perform the complete urea cycle and generate urea in cytosol?
how many N does alanine give to liver?
how many N does glutamine give to liver?
Which transporter is defective in patients with cystinuria? What is the function of it?
needed for transport of cystine
and dibasic aa - ornithine, arginine, lysine
what is the most common genetic defect pof aa metabolism?
what is Hartnup's disease?
defect in the transport of large neutral aa - tryptophan
what does low levels of tryptophan lead to?
pellagra -like symptoms
what do glucogenic amino acid leads to a degradation product of?
products that can be used for gluconeogenesis
pyruvate --> malate = gluconeogenesis
what do ketogenic amino acid leads to a degradation product of?
acetoacetyl CoA or acetyl CoA
cannot be used to gluconeogenesis
can be used for ketone body synthesis in liver
what are the 2 purely ketogenic aa?
leucine and lysine
what is transamination?
a “safe” way to transfer the α-amino nitrogen from one amino acid to an α−ketoacid which generates another amino acid. Transamination does not generate free ammonium ions which can be toxic. It transfers the nitrogen from the α-amino group to the respective α-ketoacid and verse visa.
what is deamination?
generates free ammonium ions
where is deamination mainly performed?
in the liver and kidney, where the ammonium ions are used for the urea cycle or are released into urine.
What do aminotransferases catalyze?
what do ALT need?
PLP vitamin B6
2 substraites = alpha aa and alpha keto acid
what aa does ALT use?
what aa does AST use?
what is the alpha ketoacid for alanine?
what is the alpha ketoacid for aspartate?
what is the alpha ketoacid for glutamate?
what is asparagine demainated to? by what?
what is aspartate transamination generate?
OAA (TCA cycle)
what two aa are used to form asparagine?
aspartate and glutamine
what three enzymes use free ammonia for synthesis?
carbamoyl phosphate synthase I
what is alanine derived from?
what is glutamate derived from?
what is aspartate derived from?
what is cysteine derived from?
what is tyrosine derived from?
where is arginine formed?
what is the major aa that the kidney excretes in urine?