MET 5 - Nuria Zymless

Question 1

Why should PKU patients potentially avoid certain diet drinks? [1]

Answer 1

Because they might contain the sweetener aspartame [0.5] which is made from phenylalanine and thus represents a high concentration of the amino acid [0.5]

Question 2

Why is the treatment for PKU a managed diet rather than an exclusion diet? [1]

Answer 2

Because Phenylalanine is an essential Amino acid needed to make proteins in the body and they cannot be made without it [1]

Question 3

The carbon backbone of phenylalanine is broken down to which two compounds? [2]

Answer 3

Acetoacetate (acetyl CoA can also be accepted) [1] &

Fumarate [1]

Question 4

Justify your reasoning:

What would be the chance of Nùria’s baby having PKU if her boyfriend was a carrier for PKU. [2]

Answer 4

PKU is an autosomal recessive disorder (1)

Nùria is homozygous so with a carrier boyfriend being heterozygous, here would be a 50% chance of an affected child and 50% would be carriers (1)

Question 5

Give two other supplementations that might be part of the PKU diet and, for each, give the reason why? [2]

Answer 5

• Tyrosine [0.5] because phenyalanine cannot be broken down into tyrosine in PKU patients [0.5]
• Vitamins and minerals [0.5] Since the source of Amino Acid in PKU diet is synthetic amino acid and not meat [0.5] the diet often lacks minerals and vitamins (necessary for correct metabolism).

Question 6

Considering Tyrosine metabolic pathway. Which two hormones are often low in PKU patients?

2 marks

Answer 6

Thyroid hormones (Thyroxine)

Catecholamines
[epinephrine (adrenaline),

norepinephrine (noradrenaline)

[1]