The Urea Cycle and Specialized Products Flashcards
What happens after a protein is polyubiquitinated?
it is degraded in the proteasome
Name the aa’s that are both glucogenic and ketogenic.
- Tyrosine
- Isoleucine
- Phenylalanine
- Tryptophan
What disease results when you cannot break down branched chain aa’s?
Maple Syrup Urine Disease (MSUD)
What enzyme converts arginine –> citrulline? What is the product?
- NO synthase
- NO
What does thyroid peroxidase do?
it oxidizes iodide (I-) to I2
What vitamin is essential for gamma-glutanyl carboxylase function?
vitamin K
What does it mean to be a glucogenic aa?
- it produces pyruvate, fumarate, or other Kreb Cycle intermediates
- a carbon source can be derived from it
What does muscle use to transport ammonia?
alanine
Which enzyme converts argininosuccinate –> arginine? In which cycle?
- arginosuccinate lyase
- the urea cycle
What transports ammonia thru the blood?
glutamine
What does it mean to be a ketogenic aa?
no net production of glucose (only acetyl-CoA or acetoacetate)
In the _____, bilirubin diglucuronide (conjugated bilirubin) is oxidized to stercobilin.
intestine
What is the function of thyroxin binding globulin (TBG)?
to transport T4/T3
Which enzyme converts arginine –> ornithine + urea? In which cycle?
- arginase
- in the urea cycle
What enzyme is vitamin C essential for?
for the hydroxyproline and hydroxylysine hydroxylation reactions
In the intestine, bilirubin diglucuronide (conjugated bilirubin) is oxidized to ______.
stercobilin
____ stimulates iodide uptake and stimulates release of T4/T3.
Thyroid stimulating hormone (TSH)
_____ occurs when branched-chain-a-ketoacid dehydrogenase complex is deficient, and there is consequently a buildup of the a-keto acids in urine.
Maple Syrup Urine Disease (MSUD)
What does arginosuccinate synthase do? In which cycle?
- converts citrulline + aspartate –> argininosuccinate
- in the urea cycle
_____ is used to make T4 that is then converted to T3.
Tyrosine
What does arginase do? In which cycle?
- converts arginine –> ornithine + urea
- in the urea cycle
What happens with a vitamin C deficiency?
scurvy- decreased collagen strength, decreased RBCs, easy bruising and hemorrhages
______ such as heme are cyclic molecules made of 4x pyroles primarily produced in the liver.
Porphyrins
Where is carbamoyl phosphatase synthetase I found?
the mitochondria
In the _____, bilirubin is conjugated with glucuronic acid.
liver
What enzyme is vitamin B6 required for?
aminotransferase
What oxidizes iodide (I-) to I2?
thyroid peroxidase
______ contains Tyr residues iodinated to form T4/T3.
Thyroglobulin (Tg)
In the liver, bilirubin is conjugated with ______.
glucuronic acid
What binds to porphyrins?
Fe2+
Name an allosteric activator of carbamoyl phosphatase synthetase I.
N-acetylglutamate
This transports T4/T3.
thyroxin binding globulin (TBG)
____ inhibits 2 enzymes in porphyrin synthesis leading to poisoning.
Lead
_________ is the general term for diseases in porphyrin synthesis.
Porphyrias
What enzyme converts citrulline + aspartate –> argininosuccinate? In which cycle?
- arginosuccinate synthase
- in the urea cycle
What vitamin is essential for hydroxyproline and hydroxylysine hydroxylation reactions?
vitamin C
Name 3 branched-chain aa’s. Which ones are glucogenic or ketogenic?
- leucine (ketogenic)
- valine (glucogenic)
- isoleucine (both)
What vitamin is essential for aminotransferase function?
vitamin B6
Which enzyme is vitamin K essential for?
gamma-glutanyl carboxylase
Why is bilirubin important?
it’s an antioxidant
Name the ketogenic aa’s.
- Lysine
- Leucine
What does carbamoyl phosphatase synthetase I do? In which cycle?
- converts ornithine –> citrulline
- in the urea cycle
What does arginosuccinate lyase do? In which cycle?
- converts argininosuccinate –> arginine
- in the urea cycle
What enzyme catalyzes the conversion of ornithine –> citrulline? What cycle is this part of?
- carbamoyl phosphatase synthetase I
- the urea cycle
Maple Syrup Urine Disease (MSUD) occurs when ______ is deficient, and there is consequently a buildup of the a-keto acids in urine.
the branched-chain-a-ketoacid dehydrogenase complex
