Chapter 33: Amino Acid Catabolism, Transamination and the Urea Cycle

Question 1

Body protein is turned over continually into

Answer 1

• Free amino acids

- Also originate form the diet

Question 2

Amino acids are reused or

Answer 2

• Metabolized

Question 3

The major site of amino acid metabolism is the

Answer 3

• Liver

Question 4

The amino groups are broken down to _____ then excreted as _____

Answer 4

• Ammonia and aspartate

- Urea

Question 5

The carbon skeleton of amino acids is converted to _____ and stored as _____

Answer 5

• Intermediates of metabolism

- Glycogen and fat

Question 6

Transaminase activity produces

Answer 6

• Glutamate

Question 7

_____ is removed from glutamate during the glutamate dehydrogenase step

Answer 7

• Ammonia

Question 8

The flow of nitrogen in amino acid disposal

Answer 8

• Transamination producing glutamate
• Oxidative deamination of glutamate
• Synthesis of urea

Question 9

Oxidative deamination of glutamate involves

Answer 9

• Production of ammonia (and alpha-ketoglutarate)

- Production and oxidation of glutamate dehydrogenase

Question 10

Most transaminases require _____ as an amino group acceptor

Answer 10

• Alpha ketoglutarate

Question 11

Transamination is catalyzed by

Answer 11

• Transaminases or aminotransferases

Question 12

Transamination involves the interconversion of

Answer 12

• A pair of amino acids ….

Question 13

Pyridoxal phopshate

Answer 13

• Coenzyme form of vitamin B6

- Prosthetic group of all transaminases

Question 14

Alanine transaminase is a _____ reaction

Answer 14

• Reversible

Question 15

Alanine transaminase (and aspartate transaminase) produce _____

Answer 15

• Glutamate

Question 16

Glutamate can enter

Answer 16

• The mitochondria in exhange for aspartate

Question 17

Glutamate can enter

Answer 17

• The mitochondria in exchange for aspartate

Question 18

Alanine transaminase has a key role in the _____ cycle

Answer 18

• Alanine-glucose

- Produces alanine form pyruvate in muscle that travels to the liver

Question 19

Alanine transaminase has a key role in the _____ cycle

Answer 19

• Alanine-glucose

- Produces alanine form pyruvate in muscle that travels to the liver

Question 20

The glutamate dehydrogenase enzyme converts _____ to _____

Answer 20

• Glutamate

- Alpha-ketoglutarate

Question 21

Oxidative decarboxylation of glutamate (by glutamate dehydrogenase) occurs in

Answer 21

• Inside the mitochondria

Question 22

Oxidative deamination of glutamate gnerates

Answer 22

• Alpha-ketoglutarate

- NH4+

Question 23

ADP (low energy status) and GDP and high protein consumption favor

Answer 23

• Protein degradation

- NH4+ release

Question 24

Urea is the ammonia produced in

Answer 24

• Oxidative deamination of glutamate

Question 25

Carbamoyl phosphate synthetase I catalyzes

Answer 25

• Synthesis of carbamoyl phosphate

- Entry into the urea cycle

Question 26

Carbamoyl phosphate synthetase I is a _____ enzyme

Answer 26

• Mitochondrial

Question 27

Carbamoyl phosphate synthetase I step is

Answer 27

• Irreversible

- Important regulatory step

Question 28

Carbamoyl phosphate synthetase I requires

Answer 28

• N-acetylglutamine

Question 29

Formation of carbamoyl phopshate and the synthesis of citrulline occurs in the

Answer 29

• Mitochondrial matrix

Question 30

N-acetylglutamine is produced from glutamate by

Answer 30

• Synthase

- Biotin

Question 31

Carbamoyl phosphate synthetase I is important in regulating the Urea cycle, but

Answer 31

• It is not actually part of the cycle

- Essentially makes a prerequisite for the cycle

Question 32

Carbamoyl phosphate synthetase I is important in regulating the Urea cycle, but

Answer 32

• It is not actually part of the cycle

- Essentially makes a prerequisite for the cycle

Question 33

The urea cycle occurs in the

Answer 33

• Liver

Question 34

Urea is finally made by

Answer 34

• Hydrolysis of arginine (via arginase)

- Final step

Question 35

Enzymes of the Urea cycle

Answer 35

• Carbamoyl phosphate synthetase I
• Ornithine transcarbamoylase
• Argininosuccinate synthetase
• Argininosuccinate lyase
• Arginase

Question 36

Mitochondrial carbamoyl phosphate I is key in

Answer 36

• Concentration of the substrate, NH4+

- NAG is an allosteric activator

Question 37

NAG is sythesized in the _____ from _____

Answer 37

• Mitochondria

- Acetyl-SCoA and glutamate

Question 38

The urea cycle enzymes are _____

Answer 38

• Inducible

Question 39

Total or near total loss of any urea cycle enzyme results in

Answer 39

• Death shortly arter birth

Question 40

Partial blocks of urea cycle enzymes leade to

Answer 40

• Lethargy and mental retardation

- Consequence of elevated leverls of serum glutamine and hyperammonia (24-48 hours after birth)

Question 41

_____ can clinically improve some of the milder cases

Answer 41

• Low protein diet

Question 42

Ornithine transcarbamoylase deficiency

Answer 42

• Most common deficiency

- X-linked

Question 43

Carbamoyl phosphate synthetase I deficiency causes

Answer 43

• Hyperammonia

Question 44

Arginase deficiency causes

Answer 44

• Hyperarginemia

Question 45

Argininosuccinate synthetase deficiency causes

Answer 45

• Type I citrullinemia

Question 46

Argininosuccinate synthetase deficiency causes

Answer 46

• Type I citrullinemia

Question 47

(Summary) Body protein is continually turned over, which

Answer 47

• Liberates free amino acids

Question 48

(Summary) Each amino acid can be divided into

Answer 48

• A carbon skeleton and an amino group that are metabolized differently
• Primarily metabolized in the liver

Question 49

(Summary) The process of nitrogen disposal can be divided into three segments

Answer 49

• Transamination
• Oxidative deamination
• Synthesis of non-toxic water-soluble urea (in the urea cycle of the liver)

Question 50

(Summary) Carbamoyle phosphate synthetase I is allosterically activated by

Answer 50

• N-acetylglutamate

- Primary regulatory enzyme of urea synthesis