Protein And Amino Acid Metabolism

Question 1

How many essential amino acids are there?

Answer 1

9

Question 2

Name two glucogenic AAs

Answer 2

Glycine

Glutamate

Question 3

Name two ketogenic amino acids

Answer 3

Lysine

Leucine

Question 4

Name two amino acids that are both glucogenic and ketogenic

Answer 4

Tyrosine and threonine

Question 5

Why does nitrogen need to be removed from amino acids?

Answer 5

For the carbon skeleton to be used in oxidative phosphorylation
To ensure that it can be excreted to prevent any damaged caused by ammonia

Question 6

How does the body remove nitrogen from amino acids (2ways)?

Answer 6

1. Transamination- swap amine of AA with amine of ketoacid

2. Deamination- frees amino group as free ammonia

Question 7

What is the main enzyme and keto-carboxylic acid used during transamination?
What is produced as a product?
Where does this occur?

Answer 7

Aminotransferase and alpha-ketoglutarate
Produces glutamate
In the liver

Question 8

What two enzymes that are used in transamination can be used as markers of liver function?

Answer 8

Alanine transaminase ALT

Aspartate transaminase AST

Question 9

When would LFT markers ALT and AST be raised?

Answer 9

Viral hepatitis
Autoimmune liver disease
Chronic alcoholism
Toxic injury

Question 10

Deamination of AAs can only occur when and where?

Answer 10

When the ammonia can be immediately dealt with in D-amino acids to convert them to S-amino acids so they can be used
In the liver and the kidneys

Question 11

What does a high protein diet do to the enzymes required for the urea cycle?

Answer 11

Up-regulates the enzymes

Question 12

What does a low protein diet/starvation do to the enzymes required for the urea cycle?
What consequence can this have?
What is this called?

Answer 12

Down- regulates the enzymes
Ammonia toxicity when giving someone food that has been starved
Re-feeding syndrome

Question 13

Defects of the urea cycle are caused by what?

What symptoms might a patient display?

Answer 13

Inherited (genetic)

Vomiting, lethargy, seizures, coma

Question 14

At what level do blood ammonia levels needs to be kept to prevent toxicity?

Answer 14

25-40micromol/L

Question 15

What are the two disposal mechanisms used to get rid of ammonia?

Answer 15

1. Combine with glutamate to make glutamine

2. Combine with pyruvate to make alanine

Question 16

What happens to the glutamine ad the alanine once they are produced from ammonia?

Answer 16

Glutamine goes to the liver where it is cleaved back into glutamate and ammonia, the ammonia is excreted in urine after urea cycle

Alanine goes to the liver where it is cleaved back into pyruvate, which is used to synthesise glucose and the amino group is fed into the urea cycle to be excreted in urine

Question 17

What is the name given to the condition that causes accumulation of phenyl-alanine?

Answer 17

Phenylketonuria (PKU)

Question 18

What is the underlying cause of PKU?

How does it present?

Answer 18

Phenylalanine hydroxylase deficiency
Must smell of urine
If not treated from birth: developmental delay, microcephaly, seizures, developmental delay

Question 19

How is PKU treated?

Answer 19

Using a strict diet with low phenylalanine
Avoidance of artificial sweeteners
Avoidance of high protein foods

Question 20

What condition causes a problem with the breakdown of methionine?

Answer 20

Homocystinurias

Question 21

What is homocystinuria caused by?

How does it present?

Answer 21

A defect in cystathionine beta-synthase

Affects connective tissue, muscles, CNS and CVS

Question 22

How is homocystinuria treated?

Answer 22

Low methionine diet

Avoid protein rich foods