Nitrogen Metabolism Flashcards
Intracellular amino acids in the body are __________ than extracellular concentrations.
Higher
What is the amino acid pool?
Abstraction describing the availability, distribution, and uses of amino acids.
What are the inputs to the amino acid pool: digestion of dietary proteins?
Stomach digestion, pancreatic enzymes, intestinal processing, absorption of amino acids
Protein digestion begins in the stomach. Which enzymes are involved and where do they come from?
HCl: secreted by parietal cells
Pepsinogen: secreted from chief cells
Pepsinogen is autocatalytic - a little pepsin will create more
What are the pancreatic enzymes, where are they found and what do they do?
Enteropeptidase: found in the brush border - initiates proenzyme activation cascade
Trypsinogen: converted to trypsin which activates other peptidases
Endopeptidases: complete intestinal digestion - Chymotrypsin, elastase, Carboxypeptidases
What are the enzymes associated with intestinal processing?
Aminopeptidases and dipeptidases: brush border enzymes
Intracellular peptidases target small absorbed peptides
True or false…
Amino acids are stored in the body?
FALSE! Amino acids have no formal storage.
True or false…
Ammonia is a neurotoxin.
TRUE! It is a neurotoxin, hence its need to be detoxified.
Uric acid can be reduced by which vitamin?
Vitamin C
What are the primary carbon skeletons that go to the Kreb’s cycle and ketone bodies?
a-Keto acids
What is the secondary carbon skeleton the goes into the urea cycle?
Glutamate
What are the neurotransmitters synthesized from amino acids?
GABA, Serotonin, Norepinephrine, purines & pyrimidines (nucleotides)
What are the hormones synthesized from amino acids?
Melatonin & thyroxine
What is the pigment synthesized from amino acids?
Melanin
What lipid is synthesized from amino acids?
Sphingosine
CoQ10 can regenerate which vitamin?
Vitamin E
What are the redox products synthesized from amino acids?
Glutathione & Nicotinamide
What are four end products that get excreted in the urine?
Uric acid, Creatinine, NH4+, and Urea
What is the purpose of the urea cycle?
Detoxify the body of harmful ammonia
In absorption of amino acids, co-transport of Na+ and amino acids into the brush border is driven by…
Low intracellular Na+
What are absorption disorders and what is the defect?
Cystinuria and Hartnup’s disease; they are defects in intestinal and renal uptake of amino acids
Which amino acids are specific for the only non-sodium dependent transporter?
Branched chain and aromatic amino acids
His, Met, Leu, Ile, Val, Phe, Tyr, Trp
Trypsin is the “lynch pin” for for what three digestive enzyme conversion?
Chymotrypsinogen —–> Chymotrypsin
Proelastase —–> Elastase
Procarboxypeptidases —–> Carboxypeptidase
What is the half-life range of protein?
A few minutes to several days
What are hormonal influences on protein degradation and what action do they have?
Glucocorticoids and thyroid hormones - increase degradation
Insulin -decreases degradation and increases synthesis
Proteases facilitate recycling of body proteins by which four mechanisms?
Cathepsins - lysosomes
Caspases - apoptosis
Metalloproteinases - extracellular matrix
Serine proteases - digestion and blood clotting
What is ubiquitination and what is its function?
It is a small protein (~76 amino acids) that labels cytosolic proteins for destruction.
What complexes breakdown ubiquitin-tagged proteins?
Proteasomes
