nitrogen Flashcards
do humans have a storage form of nitrogen?
- NO
- there is no protein that exists simply to store amino acids
is nitrogen itself a reactive compound?
- YES
- the body must get rid of any nitrogen above the needs
how does most nitrogen leave the body
- via the urea cycle
- retain the carbon skeletons for other uses
most nitrogens enter the body in the form of…
- amino acids
- amino acid pool
human body input of amino acid pool
- amino acids from dietary protein
- amino acids from protein turnover in the body
- synthesis of non-essential amino acids de novo
human body output of amino acid pool
- synthesis of proteins
- synthesis of nitrogen containing compounds
- use of the carbon skeleton of AA from energy
is amino acid pool balanced>
- YES
- input = output
- individual is in steady state
protein turnover in the human body
- different proteins have different half-lives
- misfolded or unstable proteins are degraded more rapidly
- half-life of a protein id determined by structure
proteasomes
- selectively degrade damaged or short-lived proteins
- energy dependent
- uses ubiquitin modification to target proteins for degradation
lysosomes
- nonselectively degrade intracellular and extracellular proteins
- literally anything that enters cell
- uses acid hydrolases to break down peptide bonds to amino acids
what is the normal intake of dietary proteins>
100g/day
where are dietary proteins digested?
- stomach
- small intestine
stomach uses what enzyme?
pepsin
small intestine uses what enzymes
-pancreatic enzymes and different ones in intestinal wall cells
transamination
-transfer of the amino acid alpha amino group to alpha ketoglutarate producing alpha keto acid and glutamate
transamination uses what enzyme?
aminotransferase
oxidative deamination
- liberation of the amino group as free amonia
- primarily occur in liver and kidney
- in mitochondria
glutamine synthetase
- free NH3 us added to glutamate to glutamine
- happens in many tissues and transports it to the liver
ALT
- transamination of pyruvate
- mainly in muscle cells
- goes to liver then turns back into pyruvate
urea cycle
- produces urea from ammonia
- primarily in liver
- 2 mitochondrial reactions
- 3 cytosolic reactions
what supplies nitrogen to the urea cycle?
-ammonia and aspartate
what is the immediate precursor for both sources of nitrogen form urea cycle?
-glutamate
hyperammonemia
- elevated levels of ammonia in the blood
- due to any defect in the urea cycle
glucogenic
- an amino acid that can be converted into pyruvate or an intermediate of the TCA cycle
- may be used as substrate for GNG and give increase in glucose formation in the liver
Ketogenic
-amino acid that can be converted into acetoacetate of precursor to acetoacetate
conditionally essential amino acids
-an amino acid that would normally be considered non essential but may become essential to meet an increased demand
essential/ non essential
essential-do not have enzymes to make it
non essesntial-can be synthesized by body
elevated homocysteine
- produced during methionine metabolism
- risk factor for occlusive vascular disease
- during pregnancy, increased incidence of neural tube defects
homocysteinuria
- deficiency of cystathionine synthase
- cant break down methionine, so it accumulates
- DISLOCATION OF LENS, glaucoma, cataracts, retinal detachment
Albinism
- defect in several different enzymes that are involved in conversion of tyrosine to melanin
- when deficiency is in tyrosinase, complete lack of pigment
