Lecture 46: Metabolism of Amino Acids Part 1 Flashcards
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.
What is Kwashiorkor translated to in English from the Ga language?
“the sickness the baby gets when the new baby comes”
What is Kwashiorkor?
It is a protein malnutrition disease and is characterized by failure to gain weight, stunted linear growth, edema, swollen abdomen, diarrhea, red hair, skin depigmentation and decreased muscle mass.
How can you treat Kwashiorkor?
Gradual reintroduction of protein and amino acids into the diet but sometimes the damages may be irreversible
What is the difference between Marasmus and Kwashiorkor?
They have similar symptoms but Marasmus is a general caloric deficiency.
What do alanine aminotransferase and aspartate aminotransferase do?
They convert alpha ketoglutarate to glutamate or reverse, respectively. During that conversion, they chance an alpha amino acid to an alpha keto acid (alanine to pyruvate and oxaloacetate to aspartate, respectively)
What is the coenzyme that is used by PLP?
pyridoxal phosphate
What is PLP converted to in the aspartate aminotransferase reaction?
pyridoxamine phosphate
What happens to ALT and bilirubin in the plasma after toxic mushroom ingestion?
ALT rises to about 20X normal until 36 hours
Bilirubin rises 36 hours after
What is unique about glutamate dehyrodgenase?
It can use both NAD+ and NADP+. (NAD+ when making AKG and NADP+ when making glutamate)
What is the allosteric inhibitor and activator (respectively) of glutamate dehyrdogenase?
GTP
ADP
What is low in schizophrenic patients?
D- serine
What are two ways that ammonia can be transported from the muscle to the liver?
- glutamine synthetase/ glutaminase
2. glucose alanine cycle
Why is glutamine a good ammonia carrier?
it has two nitrogens- alpha amino group and amide nitrogen
