Amino Acid Metab

Question 1

Rate limiting enzyme in the urea cycle

Answer 1

CPS I

Question 2

Aspartate combines with alpha-ketoglutarate to form glutamate and what?

Answer 2

oxaloacetate

Question 3

Alanine combines with alpha-ketoglutarate to form glutamate and what?

Answer 3

pyruvate

Question 4

What is the point of the aspartate/alanine aminotransferases in conjunction with glutamate?

Answer 4

Shuttle amino groups through glutamate, ultimately pushing ammonia to the urea cycle

Question 5

Key cofactor for transaminases

Answer 5

Pyridoxal phosphate (Vitamin B6)

Question 6

Shuttling of amino acids between muscle and liver uses what process?

Answer 6

Transamination shuttling (via alanine in this instance)

Question 7

Enzyme catalyzing Glutamate to alpha-Ketoglutarate, ejecting an ammonia in the process

Answer 7

Glutamate dehydrogenase

Question 8

Regulators of glutamate dehydrogenase which increase its activity (2)

Answer 8

ADP and GDP

Question 9

Regulators of glutamate dehydrogenase which decrease its activity (2)

Answer 9

ATP and GTP

Question 10

Allosteric activator of Carbamoyl phosphate synthetase I (CPS I)

Answer 10

N-acetylglutamate

Question 11

What is N-acetylglutamate synthesized from?

Answer 11

Acetyl CoA and glutamate

Question 12

How is citrulline formed in the urea cycle? (two inputs and enzyme)

Answer 12

Condensation of ornithine with carbamoyl phosphate. Catalyzed by Ornithine Transcarbamoylase (Step 2)

Question 13

What provides the second ammonia nitrogen in the synthesis of urea?

Answer 13

Aspartate (in the step catalyzed by arginosuccinate synthetase)

Question 14

Arginine is the precursor to urea. What is added and by what enzyme to form ornithine and urea?

Answer 14

H20. The enzyme is Arginase

Question 15

What TCA intermediate is a net product of the urea cycle?

Answer 15

fumarate

Question 16

Six amino acids which breakdown to pyruvate

Answer 16

1) Alanine
2) Cysteine
3) Glycine
4) Serine
5) Threonine
6) Tryptophan

Question 17

Amino acids which breakdown into alpha-ketoglutarate (5)

Answer 17

1) Glutamine
2) Proline
3) Arginine
4) Histidine
5) Glutamate

Question 18

Amino acids which breakdown into Succinyl CoA (4)

Answer 18

1) Isoleucine
2) Methionine
3) Threonine
4) Valine

Question 19

Amino acids which breakdown into Fumarate (3)

Answer 19

1) Aspartate
2) Phenylalanine
3) Tyrosine

Question 20

Two exclusively ketogenic amino acids

Answer 20

Leucine and Lysine

Question 21

Amino acids which breakdown into Acetyl CoA (3)

Answer 21

1) Isoleucine
2) Leucine
3) Tryptophan

Question 22

Amino acids which breakdown into Acetoacetyl CoA (5)

Answer 22

1) Leucine
2) Lysine
3) Phenylalanine
4) Tryptophan
5) Tyrosine

Question 23

What important intermediates arise from the breakdown of methionine? (2)

Answer 23

S-adenosyl methionine (methyl group transfer) and homocysteine

Question 24

Relatively benign condition resulting from a deficiency of the oxidase that breaks open homogentisate (intermediate in Tyr/Phe catabolism). Homogentisate accumulation colors urine.

Answer 24

Alcaptonuria

Question 25

Treatment for alcaptonuria

Answer 25

Dietary restriction of Phenylalanine and Tyrosine alongside large doses of ascorbic acid

Question 26

Deficiency of phenylalanine hydroxylase, leading to a buildup of phenylalanine (20x normal). Causes severe mental retardation.

Answer 26

Phenylalanine