Protein and amino acid metabolism

Question 1

Give an example of a glucogenic amino acid.

Answer 1

Alanine

Question 2

Give an example of a ketogenic amino acid.

Answer 2

Lysine

Question 3

Give an example of an amino acid that is both glucogenic and ketogenic.

Answer 3

Tryptophan

Question 4

What effect does insulin have on protein synthesis?

Answer 4

It increases protein synthesis

Question 5

What effect does glucocorticoids such as cortisol have on protein synthesis?

Answer 5

It deceases protein synthesis

Question 6

Why can Cushing’s syndrome lead to striae?

Answer 6

There is excess cortisol stimulating excessive protein breakdown

Question 7

Glutamate is a precursor for …….

Answer 7

GABA

Question 8

Tryptophan is a precursor for serotonin. True or false?

Answer 8

True

Question 9

What are the two main pathways to facilitate nitrogen removal?

Answer 9

Transamination and deamination

Question 10

All aminotransferases are a derivative of vitamin ….

Answer 10

Vitamin B6

Question 11

Which enzyme uses oxaloacetate as a substrate instead of a-ketoglutarate? (Transamination)

Answer 11

Aspartate aminotransferase

Question 12

What is the name of the two key aminotransferases associated with liver function? And what is their role?

Answer 12

Alanine aminotransferase (ALT)- Converts alanine to glutamate
Aspartate aminotransferase (AST)- Converts glutamate to aspartate

Question 13

Where does deamination occur?

Answer 13

The liver and the kidney

Question 14

Which two amino acids can enter the urea cycle?

Answer 14

Glutamate and aspartate

Question 15

Is the urea cycle regulated?

Answer 15

No. It is inducible but not regulated.

Question 16

What is a glucogenic amino acids?

Answer 16

Amino acids that can be converted to glucose via gluconeogenesis

Question 17

What are ketogenic amino acids?

Answer 17

Amino acids that can be degraded directly into acetyl CoA which is the precursor of ketone bodies.

Question 18

What causes refeeding syndrome?

Answer 18

Ammonia toxicity due to the down-regulation of the urea cycle

Question 19

Defects in the urea cycle leads to what?

Answer 19

Hyperammonia and accumulation/excretion of urea cycle intermediates

Question 20

What are the symptoms of hyperammonemia?

Answer 20

Vomiting, lethargy and irritability

Question 21

Which organ is ammonia very toxic to and why is it toxic?

Answer 21

It is toxic to the brain and disrupts cerebral blood flow as well as altering the blood-brain barrier.

Question 22

Ammonia can combine with which amino acid to move from the periphery to the liver or kidney for disposal?

Answer 22

Glutamate. It combines with glutamate to form glutamine via Glutamine synthase.

Question 23

Which enzyme is deficient in PKU?

Answer 23

Phenylalanine hydroxylase

Question 24

What accumulates in PKU and how is it excreted?

Answer 24

Phenylalanine accumulates and phenylketones are consequently seen in the urine

Question 25

What are the symptoms of PKU?

Answer 25

Sever intellectual disability, developmental delay, microcephaly, seizures and hypopigmentation

Question 26

How do you treat PKU?

Answer 26

Low phenylalanine diet

Question 27

What are homocystinurias?

Answer 27

Problems breaking down methionine

Question 28

Which enzyme is commonly defective in homocystinuria?

Answer 28

Cystathionine B-synthase

Question 29

What parts of the body does homocystinuria effect?

Answer 29

Connective tissues, muscles, CNS and CVS

Question 30

How do you treat homocystinurias?

Answer 30

Low methionine diet

Question 31

What would you find in the urine of someone suffering from homocystinuria?

Answer 31

Homocystine

Question 32

What is commonly use an indicator of renal function?

Answer 32

Creatinine