Lecture 46: Metabolism of Amino Acids Part 1 Flashcards
(37 cards)
What are two sources of the amino acid pool?
dietary protein
body protein
How much smaller is plasma amino acid concentration than plasma glucose?
4X
What are the ten essential amino acids?
Threonine Tryptophan Arginine Phenylalanine Leucine Valine Histidine Lysine Isoleucine
Why is arginine special?
It is not always considered essential because it can be made in the body.
What are two hormones that are secreted after gastric contents enter the small intestine?
Cholecystokinin
Secretin
What does cholecystokinin and secretin do?
They release pancreatic enzymes and cholecystokinin also releases bicarb and bile (for lipids)
What are the dibasic amino acids?
Ornithine
Arginine
Lysine
What is cystinuria?
it is when the transporter for cystine, ornithine, arginine and lysine are defective and appear in the urine.
disorder of the proximal convoluted tubule
Leads to accumulation and precipitation of stones in tract (and blockage)
What are kidney stones usually made of? What are they made of in cystinuria?
calcium oxalate
cystine (usually soluble in H2O but because of high concentrations it approaches limit of solubility and will precipitate out to form calculi)
What is the incidence of cystinuria?
1/7000; autosomal recessive
T/F: Cysteine has a double bond.
False. Cystine has the double bound.
What is the major reductant inside cells?
Glutathione (5mM)
Why would you not find cystine in the cytosol?
You would find cysteine (reduced sulfahydral containing form) because it is a reducing environment.
Why do you get disulfide bond formation in the ECF?
It is an oxidizing environment. Cystine would be the major form.
Where are disulfide linked proteins usually found?
They are found in the plasma membrane because the cytosol is too reductive an environment. The sulfide portion faces outwards from the cell.
What is an example of a disulfide linked peptide hormone?
Insulin (made on the RER -for export- and lumen is not exposed to glutathione)
What causes pellagra?
It is caused by a deficiency of niacin which is needed to make NAD+ and NADP+.
What are the symptoms of pellagra?
Dermatitis
Diarrhea
Dementia
(if untreated) Death
What is a metabolite of tryptophan?
Quinolinate
What can defective tryptophan absorption result in?
Hartnup
Why does pellagra and Hartnup have similar symptoms?
Both tryptophan metabolites and niacin are needed to make NAD+/ NADP+ and it is this deficiency that causes problems with CNS, GI tract and skin.
When is there usually a positive nitrogen balance in the body?
during pregnancy or growth
When is there a negative N balance?
protein deficiency
essential amino acid deficiency
wasting diseases, burns, trauma
T/F: A normal adult is in nitrogen equilibrium.
TRUE.
