Lecture 33 - Amino Acid Metabolism I

Question 1

Degradation and re-synthesis of proteins.

Answer 1

protein turnover

Question 2

These are organelles that are important in protein turnover. They physically degrade proteins, usually by means of acidification or peroxide.

A. proteosome
B. ubiquitin
C. lysozome
D. hydrolase

Answer 2

C. lysozome

Question 3

These act as a molecular “garbage can” and degrade proteins that have been marked by molecular “tags.”

A. proteosome
B. ubiquitin
C. lysozome
D. hydrolase

Answer 3

A. proteosome

Question 4

The urea cycle is important in the removal of _____ from blood.

a. nitrogenous compounds
b. amino acids
c. amino groups

Answer 4

c. amino groups

Question 5

Removal of the ammonium group from an amino acid occurs via a two step process. Step 1 is the transfer of the NH3 to ______.

Answer 5

glutamate (deamination)

Question 6

Step 2 of amino acid metabolism is the ___________

Answer 6

release of NH4 (ammonium) from glutamate (dehydrogenation)

Question 7

_____ is required to accept the NH3 from glutamate

A. Vitamin B6 (pyridoxine)
B. Vitamin B3
C. NAD

Answer 7

B. B3

Question 8

________ is required to accept the NH3 from amino acids.

A. Vitamin B6 (pyridoxine)
B. Vitamin B3
C. NAD

Answer 8

A. Vitamin B6 (pyridoxine)

Question 9

____ serves as a co-factor to cleave NH3 from glutamate.

A. Vitamin B6 (pyridoxine)
B. Vitamin B3
C. NAD

Answer 9

C. NAD

Question 10

The reaction removing NH3 from glutamate occurs in ____.

A. muscle
B. brain
C. liver

Answer 10

C. liver

produces urea

Question 11

DRAW THE UREA CYCLE.

Answer 11

Check your drawing

Question 12

Citrulline + Asp = _______________

Answer 12

argininosuccinate

Question 13

argininosuccinate is degraded to _____________

Answer 13

fumarate

Question 14

A patient presents with large amounts of ornithine in the blood. What enzyme is most likely deficient?

Answer 14

ornithine transcarbamoylase

Question 15

A patient presents with elevated arginine levels. What enzyme is deficient?

Answer 15

argininase I

Question 16

A patient would except to have low levels of fumarate in what enzyme deficiency?

Answer 16

argininosuccinate lyase

Question 17

A patient would have large amounts of aspartate in what enzyme deficiency?

Answer 17

Argininosuccinate synthetase (uses aspartate and citrulline to form argininosuccinate)

Question 18

From what source does urea obtain its nitrogen?

Answer 18

ammonium and aspartate

Question 19

from what source does urea obtain its carbon?

Answer 19

CO2

Question 20

The product of the arginine to ornithine reaction in the urea cycle can be used as a measurement of liver function. What is the product and what is the test?

Answer 20

urea; blood urea nitrogen

Question 21

Explain why NH4+ is toxic to the nervous system?

Answer 21

In order to remove excess NH4 from the nervous system, the urea cycle must be run almost continuously. This results in decreased NADPH, decreased alpha-ketogluterate (a TCA intermediate), and decreased ATP.

This has the overall effect of “de-energizing” the brain.

Question 22

What amino acid is primarily used in transporting NH4 in the brain?

Answer 22

Glutamine

Question 23

What AA is used to transport NH4 in the liver?

Answer 23

Alanine

Question 24

What two enzymes are solely ketogenic?

Answer 24

lysine and leucine

Question 25

Following the removal of NH3 from proteins, the _________ may be used as fuel molecules.

A. carbon skeletons
B. carbonyl
C. carboxylic acid group

Answer 25

A. carbon skeletons

Question 26

What is the mechanism behind NS damage in hyperammonemia?

Answer 26

Defects in the urea cycle produce large amounts of urea.

This will inactivate the neuronal Na/K/Cl ATPase pumps, changing cellular osmolarity.

This osmolarity change results in the swelling/rupture of neurons.

Question 27

Solely ketogenic AAs

Answer 27

Lysine (K)

Leucine (L)

Question 28

Both ketogenic and glycogenic AAs

Answer 28

Frank, will you interpret?

F- phenylalanine
W-Twyptophan
Y-tYrosine
I-Isoleucine