Amino Acid Degradation

Question 1

Four events involved in formation of urea

Answer 1

1. Transamination and formation of alanine & glutamate
2. Transport of nitrogen into the liver
3. Transamination and Deamination in liver
4. Ureas cycle

Question 2

Where is the urea cycle

Answer 2

In hepatoctyes

Question 3

In what two compartments of the cells does the urea cycle span

Answer 3

Mitochondria and cytsol

Question 4

Function of transaminases

Answer 4

Transfer an amino group from one molecule to another

Question 5

Two main amino acids from which an amino group is taken during transamination

Answer 5

Alanine and Aspartate

Question 6

Which molecule is the removed amino group usually transferred to

Answer 6

alpha- ketoglutarate

Question 7

Which new amino acid is usually formed during transamination

Answer 7

glutamate

Question 8

Which transaminase is used which alanine

Answer 8

Alanine transaminase

Question 9

Which transaminase is used which aspartate

Answer 9

Aspartate transaminase

Question 10

Which substance is needed to mediate transfer during transamination

Answer 10

Pyridoxal phosphate (PLP)

Question 11

What is pyridoxal phosphate derived from

Answer 11

Vitamin B6

Question 12

Which two amino acids do not participate in transamination

Answer 12

Lysine and threonine

Question 13

What two substances in amino acid metabolism in a clinical indicator for liver damage

Answer 13

Aspartate transaminase and Alanine transaminase

Question 14

Which molecule transports amino acid nitrogen to the liver

Answer 14

Glutamine

Question 15

Which two molecules combine to form Glutamine

Answer 15

Glutamate and ammonia

Question 16

Which enzyme is needed for the formation of glutamine

Answer 16

Glycine synthetase

Question 17

Which tissues require glutamine to transport nitrogen to the liver

Answer 17

Brain, muscle and adipose tissue

Question 18

What is the importance of glutamine in the brain

Answer 18

To remove excess nitrogen and prevent ammonia toxicity

Question 19

Two processes by which ammonia is obtained for the urea cycle

Answer 19

Deamination of glycine and oxidative deamination of glutamate

Question 20

Which reaction requires glutaminase

Answer 20

Conversion of glutamine to glutamate

Question 21

Which reaction requires glutamate dehydrogenase

Answer 21

Conversion of glutamate to alpha-ketoglutarate

Question 22

Which of the two reaction that sequesters ammonia is reversible

Answer 22

Conversion of glutamate to alpha-ketoglutarate

Question 23

Where does detoxification of ammonia occur

Answer 23

liver

Question 24

The nitrogen atoms contained in urea come from which substances

Answer 24

free ammonia and aspartate

Question 25

How is aspartate formed

Answer 25

Transamination of glutamate with oxaloacetate in the presence of AST

Question 26

How is ammonia formed in the intestine

Answer 26

Bacterial urease makes ammonia

Question 27

How is ammonia produced in the intestine transported to the liver

Answer 27

Travels through portal blood to the liver

Question 28

Four immediate sources of ammonia for the urea cycle

Answer 28

1. Deamination of glutamine
2. Oxidative deamination of glutamate
3. Bacterial urease in intestine
4. Transamination of glutamate with oxaloacetate

Question 29

Six main products of the urea cycle

Answer 29

1. carbamoyl phosphate
2. Citrulline
3. Argininosuccinate
4. Argininosuccinate
5. Urea
6. Ornithine

Question 30

What activates N-acetylglutamate synthase

Answer 30

Arginine

Question 31

Function of acetylglutamate synthase

Answer 31

Coverts glutamate to acetylglutamate

Question 32

What activates Carbamoyl
phosphate
synthetase I

Answer 32

N-acetylglutamate

Question 33

Starting molecules for the urea cycle

Answer 33

NH4, HCO3, 2ATP

Question 34

What converts Carbamoyl phosphate to Citrulline

Answer 34

Ornithine

transcarbamoylase

Question 35

What converts Citrulline to Argininosuccinate

Answer 35

Argininosuccinate

synthetase

Question 36

What converts Argininosuccinate to Arginine

Answer 36

Argininosuccinate

lyase

Question 37

When aspartate gives up its amino group in the urea cycle what molecule does it become

Answer 37

Fumarate

Question 38

What converts Arginine to Ornithine

Answer 38

Arginase

Question 39

When is urea produced in the urea cycle and what enzyme controls this step

Answer 39

Conversion of Arginine to Ornithine with the enzyme arginase

Question 40

At which steps in the urea cycle are ATP molecules utilized

Answer 40

1. Conversion of Carbamoyl phosphate to Citrulline

2. Conversion of Citrulline to Argininosuccinate

Question 41

Causes of hyperammonemia

Answer 41

1. Congenital hyperammonemia
2. Acquired hyperammonemia
3. Liver disease (alcohol cirrhosis, hepatitis)
4. Shunting of blood from portal system to systemic circulation

Question 42

Which inherited disease of the urea cycle is X-linked recessive

Answer 42

Ornithine Transcarboxylase deficiency

Question 43

How does Ornithine Transcarboxylase deficiency lead to excretion of orotic acid

Answer 43

Carbamoyl phosphate builds up and enters the cytosol to go into pyrimidine synthesis which produces orotic acid

Question 44

Treatments for hyperammonemia

Answer 44

1. low protein diet
2. Phenylbutyrate
3. benzoic acid

Question 45

How does Phenylbutyrate treat hyperammonemia

Answer 45

Phenylbutyrate gets converted to phenylacetate, which binds to glutamine for phenylacetylglutamate that gets excreted

Question 46

How does benzoic acid treat hyperammonemia

Answer 46

Benzoic acid binds to glycine and turn into hippuric acid which gets secreted