additional thoughts Flashcards
Which two desaturases do humans lack?
12 and 15
How many rounds of FA synthesis does it take to get palmitate?
7 - 4c added the first time, 2c added the rest
Additonal FA elongation and desaturation occurs in what part of the cell?
Endoplasmic reticulum
What proteolytic enzyme is in the stomach?
pepsin
What proteolytic enzymes are in the small intestine?
trypsin, chymotrypsin, elastase
Why is the pH of the stomach important?
- zymogens become active at low pH, allowing them to act on amino acids and degrade them, acid also denatures proteins
What is the proteasome involved in digestion?
ubiquitin proteasome
What proteolytic enzyme is secreted from gastric cells?
pepsin(ogen)
What proteolytic enzyme is secreted from the pancreas?
trypsinogen, chymotrypsinogen, proelastase
What is excess ammonia in non liver tissues transported as? What happens after?
Glutamine
- glutamine synthetase adds an NH4 group to glutamate to make glutamine
- glutamine is shuttled into the liver
- glutamine is converted to glutamate in liver mito by glutaminase which releases NH4 to the urea cycle
What organ can excrete ammonia directly?
kidney
Aminotransferases can be used as diagnostic markers for?
liver damage, SGPT and AGOT diagnostic tests are used, elevated levels in blood can be markers for heardt attack
Nitrogen can be removed in what three forms?
ammonium, urea, uric acid
What can urea cycle enzyme deficiencies cause?
hyperammonemia or elevated NH4 in the blood, occurs with liver cirrhosis as well
What are two possible suplements for urea deficiencies?
benzoate and phenylbutyrate, bind to glycine and glutamine which can be peed out
- helps delete liver nitrogen pool
In the liver, what two amino acids can directly produce ammonia by breakdown?
serine and threonine
What does maple syrup urine disease result from?
liver lacking branched chain aminotransferases, causing aa breakdown to occur in brain, toxic = deathq
What is PKU disorder?
defect in phenylalanine hydroxylase - causes phenylalanine buildup in blood, sever mental defects
What is the primary control point in nitrogen metabolism, what are three negative allosteric regulators?
glutamine synthetase, carbamoyl phosphate, alanine, CTP
Glutamine synthetase is active in its ____ form
deadenylated
Where does the CH3 group come from in the conversion of homocysteine to methionine?
N5 of thf
What enzyme is the allosterically regulated control point for pyrimidine biosynthesis?
aspartate transcarbamoylase - carbamoylphosphate to carbamoyl aspartate
After forming carbamoyl aspartate, what is the next step in pyrimidine synthesis?
conversion to dihydroorate via dihydroorotate synthetase
What is PRPP and how is it formed?
Is ribose 5 phosphate with atp joining to drop off 2 po4 groups, formed by PRPP synthetase, used in pyrimidine and purine synthesis
What is 5 fluorouracil?
suicide inhibitor of thymidylate synthetase - cant make TMP
What is gout?
high blood levels of uric acid
What causes lesch nyhan syndrome?
deficiency in HGPRT which is main enzyme in purine salvaging, severe disability
How is PKU typically treated?
diet
What two enzymes produce ammonia in the kidney?
glutamate dehydrogenase and glutaminase
THF is involved in what two kinds of biosynthesis>
Methionine and thymidylate (pyrimidines)
What is the main drug that can inhibit dihydrofolate reductase which turns dihydrofolate to tetrahydrofolate
methotrexate - treats arthritis and eczema
What amino acid is procudes as a byproduct of methionine biosynthesis?
adenosine
What amino acid is the source of methyl groups in methionine biosynthesis?
Homocysteine / N5 methylthf
WHAT COFACTOR IS REQUIRED FOR METHIONINE BIOSYNTHESIS?
Coenzyme b12
Why is arginine conditionally essential?
supplied by the urea cycle in the arginosuccinase reaction
Biotin is a required cofactor for what enzyme
Acetyl CoA carboxylase
