Aubert Small Group

Question 1

Is the following condition associated with a positive or negative nitrogen balance, or with nitrogen equilibrium: A normal, healthy adult

Answer 1

Equilibrium

Question 2

Is the following condition associated with a positive or negative nitrogen balance, or with nitrogen equilibrium: A growing child

Answer 2

Positive

Question 3

Is the following condition associated with a positive or negative nitrogen balance, or with nitrogen equilibrium: A pregnant woman

Answer 3

Positive

Question 4

Is the following condition associated with a positive or negative nitrogen balance, or with nitrogen equilibrium: Following trauma

Answer 4

Positive and negative: immediately after will be negative, a long time after it will be positive

Question 5

Is the following condition associated with a positive or negative nitrogen balance, or with nitrogen equilibrium: During regeneration of damaged tissue

Answer 5

Positive

Question 6

Is the following condition associated with a positive or negative nitrogen balance, or with nitrogen equilibrium: During starvation

Answer 6

Negative

Question 7

Is the following condition associated with a positive or negative nitrogen balance, or with nitrogen equilibrium: During chronic ingestion of large amounts of carbohydrates, but no protein

Answer 7

Negative

Question 8

Is the following condition associated with a positive or negative nitrogen balance, or with nitrogen equilibrium: Chronic ingestion of apparently adequate amounts of protein, but the protein is deficient in one of the essential amino acids

Answer 8

Negative

Question 9

Is tyrosine nutritionally essential or non-essential? How can you tell from its degradative pathway?

Answer 9

Non-essential because it forms from phenylalanine

Question 10

What cofactor is required for phenylalanine hydroxylase, the first enzyme in the degradative pathway of phenylalanine

Answer 10

Tetrahydrobiopterin, it supplies 2 H+

Question 11

What type of reaction is the step in which tyrosine is enzymatically converted to p-hydroxyphenylpyruvic acid?

Answer 11

A transamination

Question 12

Are phenylalanine and tyrosine glucogenic, ketogenic, or both?

Answer 12

Both

Question 13

What enzyme is defective in PKU?

Answer 13

Phenylalanine hydroxylase

Question 14

What is the result of untreated PKU?

Answer 14

Mental retardation, abnormal EEG, seizures, extreme hyperactivity, and psychoses

Question 15

What would you see in the lab assay of a newborn being tested for PKU who had the disease

Answer 15

Growth of a phenylalanine dependent strain of bacteria

Question 16

Why did the infant need to consume milk prior to being tested for PKU

Answer 16

because the fetus would have normal phenylalanine levels since the mother would have the hydroxylase

Question 17

What would cause the formation of phenylpyruvic acid?

Answer 17

A transamination reaction to relieve the buildup of toxic phenylalanine

Question 18

Is tyrosine nutritionally essential or non-essential in PKU?

Answer 18

essential because phenylalanine cannot be broken down to produce it

Question 19

Suggest a dietary treatment for classic PKU

Answer 19

Avoid foods with aspartame/artificial sweeteners, still need about 1% of phenylalanine

Question 20

Why are diet sodas supplied with a package warning for phenylketonurics

Answer 20

Because aspartame is a methyl-ester of the aspartic acid-phenylalanine dipeptide

Question 21

What are the 3 causes of PKU?

Answer 21

1. defect in the synthesis of tetrahydrobiopterin
2. deficiency in dihydropteridine reductase
3. defect in the enzyme phenylalanine hydroxylase

Question 22

Why would a defect in the synthesis of tetrahydrobiopterin or deficiency in dihydropteridine reductase result in hyperphenylalaninemia?

Answer 22

The cofactor for the breakdown of phenylalanine wouldn’t be available

Question 23

What causes hyperammonemia in newborns?

Answer 23

When N-acetylglutamate synthase is deficient and working at <5% of normal levels

Question 24

Why would an N-acetylglutamate synthase deficiency cause hyprammonemia

Answer 24

N-acetylglutamate regulates urea production. If urea production is decreased, then there will be a buildup of ammonia.

Question 25

Why does carbaglu decrease ammonia levels

Answer 25

Carbaglu is similar to N-acetylglutamate, so it can help regulate the urea cycle