Lecture 23 - Detoxification of Ammonia: Urea and Glutamine Synthesis Flashcards Preview

Fuel Metabolism - 2016 > Lecture 23 - Detoxification of Ammonia: Urea and Glutamine Synthesis > Flashcards

Flashcards in Lecture 23 - Detoxification of Ammonia: Urea and Glutamine Synthesis Deck (23):
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

Both benzoate and phenylacetate promote alternative pathways of ______.

nitrogen elimination