Flashcards in Lecture 23 - Detoxification of Ammonia: Urea and Glutamine Synthesis Deck (23)
Loading flashcards...
1
Glutamine is a nontoxic transporter of the __________ ion from extrahepatic tissue to the liver.
ammonium
2
Excess glutamine is degraded in the liver to a-KG and NH4+, where the ammonia is converted to:
urea
3
Glutamate is converted to glutamine by the _____________ enzyme using ATP.
glutamine synthetase
4
Glutamate is converted to glutamine in the cytosol of all tissues, but especially ______.
the brain (!)
5
Which type of hepatocytes are found near the portal vein of the liver?
periportal hepatocytes
6
Which type of hepatocytes are found near the central vein of the liver?
perivenous hepatocytes
7
Which is found in the mitochondria of periportal hepatocytes?
A. CPS-I
B. CPS-II
C. Glutamine synthetase
A
8
Which is found in the cytosol of perivenous hepatocytes?
A. CPS-I
B. CPS-II
C. Glutamine synthetase
C
9
__________ is allosterically activated by ammonium ions.
A. CPS-I
B. CPS-II
C. Glutamine synthetase
D. Glutaminase
D
10
What are the two precursors of the nitrogen atoms in the urea?
1. aspartate
2. ammonium ion
11
The carbon and oxygen atoms (in the form of a carbonyl group) in urea come from a _______ ion.
bicarbonate
12
What are 3 properties of urea that make it a good physiologic choice as a molecule for disposal of waste nitrogen?
1. Nontoxic product
2. Dissolves easily in water - polar
3. Easy to synthesize (low energy cost)
13
Both ureagenesis and gluconeogenesis happen in the _____.
liver
14
The energy cost for synthesizing each molecule of urea is:
4 high energy phosphate bonds
15
_________ from skeletal muscle is used to transport ammonia for ureagenesis to the liver, and then is used to regenerate pyruvate in the liver.
Alanine
16
Hyperammonemia Type I is a defect in:
A. CPS-I
B. OTCase
C. Argininosuccinate synthase
D. Argininosuccinate lyase
A - Hyperammonemia Type I is low plasma citrulline, LOW urinary orotate.
17
Hyperammonemia Type II is a defect in:
A. CPS-I
B. OTCase
C. Argininosuccinate synthase
D. Argininosuccinate lyase
B - Hyperammonemia Type II is low plasma citrulline, HIGH urinary orotate.
18
Citrullinemia is a defect in:
A. CPS-I
B. OTCase
C. Argininosuccinate synthase
D. Argininosuccinate lyase
E. Arginase
C - citrullinemia is high plasma citrulline.
19
Argininosuccinic aciduris is a defect in:
A. CPS-I
B. OTCase
C. Argininosuccinate synthase
D. Argininosuccinate lyase
E. Arginase
D - Argininosuccinic aciduris is medium plasma citrulline, argininosuccinate, and anhydrides in plasma.
20
_______ is low plasma citrulline and high urinary orotate.
A. Hyperammonemia Type I
B. Hyperammonemia Type II
C. Citrullinemia
B
21
Short term regulation of the urea cycle is exerted at the level of what enzyme?
carbamoyl phosphate synthetase I (CPS-I)
22
Long term regulation of the urea cycle depends on changes in the levels of ____________.
urea cycle enzymes
23
