Protein Metabolism

Question 1

Removal of the a-amino group is a process called _________?

Answer 1

Deamination

Question 2

What are the sources of the nitrogen that appears in urea?

Answer 2

NH3, Primarily from acid catabolism,
provides one N urea and Asp provides the other.

Question 3

Asparginase is used to treatchildhood acute lymphoblastic leukemia.
What is the biochemical basis of this treatment?

Answer 3

Asparginase is a treatment for ALL because it deamidates circulating Asn to Asp.
Rapidly dividing leukemia cells require Asn for growth and have limited capacity to synthesize it.

Question 4

What coenzymes are required by BCKD, the enzyme that oxidatively decarboxylates the alpha-keto acid derivatives of the BCAA’s?

Answer 4

BCKD ,a mitochondrial enzyme, requires:
Co-substrate:
1. NAD
2. CoA
Prosthetic groups:
1. TTP
2. Lipoic acid
3. FAD

BC ka Dae?
(Na Co, True Love FADe)

Question 5

This is the phase where carbon skeletons of a-keto acids are converted to common intermediates of energy producing metabolic pathways.

Answer 5

Second Phase of AA Catabolism

Question 6

Identify the enzyme used in oxidative deamination.

Answer 6

Glutamate dehydrogenase

Question 7

Identify the AA which do not undergo transamination?

Answer 7

1. Lysine
2. Threonine
3. Proline
4. Hydroxyproline

(HTLP)

Question 8

Urea cycle happens in which organ of the body?

Answer 8

Liver only

Question 9

Urea cycle happens in which part/s of the cell?

Answer 9

It occurs in both mitochondria and cytosol

Question 10

Identify the substrates used in urea cycle.

Answer 10

1. NH3
2. Aspartate
3. CO2

Question 11

This is the allosteric activator for the rate limiting step in urea cycle.

Answer 11

N-acetylglutamate

Question 12

What is the most common hereditary hyperammonemia?

Answer 12

Ornithine transcarbomylase deficiency

Question 13

What are the 2 purely ketogenic AAs?

Answer 13

1. Lysine
2. Leucine

( II ketogenic)

Question 14

Ketoacid of pyruvate

Answer 14

Alanine

Question 15

Ketoacid of oxaloacetate

Answer 15

Aspartate

Question 16

Ketoacid of a-ketoglutarate

Answer 16

Glutamate

Question 17

Carnitine comes from which amino acid?

Answer 17

Lysine

Question 18

Identify the derivatives of Methionine.

Answer 18

1. S-adenosylmethionine
2. Creatine
3. Polyamines

Question 19

Identify the derivatives of Tryptophan.

Answer 19

1. Serotonin
2. Niacin
3. Melatonin

( Tryp Mo Sya No? )

Question 20

Alkaptonuria is a congenital deficiency of __________ in the degradative pathway of tyrosine, leading to build up of homogentisic acid.

Answer 20

Homogentisate oxidase

Question 21

Identify the disease associated with defect in fumarylacetoacetate hydrolase?

Answer 21

Tyrosinemia Type I

Question 22

Cystinuria is an inherited defect of renal tubular amino acid transporter for ________,__________,___________ and __________ in the PCT of the kidneys.

Answer 22

1. Cysteine
2. Ornithine
3. Lysine
4. Arginine

( COLA)

Question 23

Identify the co-factor of ALA Synthase.

Answer 23

Vitamin B6 / Pyridoxine / Pyridoxal-5-Phosphate

Question 24

Lead inactivates which two enzymes in the heme synthesis pathway?

Answer 24

1. ALA Dehydratase
2. Ferrochelatase

Question 25

Porphyria cutanea tarda is the deficiency of which enzyme?

Answer 25

Uroporphyrinogen Decarboxylase

Question 26

Acute intermittent porphyria is the deficiency of which enzyme?

Answer 26

Hydroxymethylbilane decarboxylase/
Uroporphyrinogen I synthase

Question 27

What is the basis of ethanol- related hypoglycemia?

Answer 27

The rise in NADH/ NAD+ ratio as a result of ethanol metabolism by ADH and ALDH, enzymes that oxidize ethanol and acetaldehyde, respectively, as their coenzyme NAD+ is reduced.

Question 28

What group of amino acid is metabolized primarily by muscle rather than by liver?

Answer 28

Branched Chain Amino Acids are catabolized primarily by muscles, the primary location of BCAA transaminase that initiates their degradation.

BCAAs: Leucine, Isoleucine, Valine

Question 29

True or False. Peptide transport protein allows uptake of dipeptide and tripeptides.

Answer 29

True. Peptides are largely digested in the cytosol. Constituent AAs for export to the body.

Question 30

Amino acid that is likely elevated in a child with relatives having darkening of the urine when left standing?

Answer 30

Homogentisate
Alkaptonuria: is caused by a defective homogentisic acid oxidase.

Question 31

Amino acid that is likely increased in the urine in a child with mental retardation, difficulty with vision, fair complexion, malar erythema, bilateral dislocated lenses, long slender hands with blood test cystathione concentration below normal.

Answer 31

Ans. Methionine
Homocystinuria: homocysteine is a metabolite of methionine

Question 32

Mechanism on how lactulose acts to treat hyperammonemia.

Answer 32

Fermentation of lactulose results in acidification of gut contents so that ammonia produced by intestinal bacteria is trapped as ammonium that cannot be diffused into the blood stream.

Question 33

Enzyme that is defective in an infant experiencing feeding difficulty, generalized hypotonia of the limbs , strange eye movements causing eyeballs to rotate up several times a day with significant aminoaciduria and aminoacidemia.

Answer 33

L- amino acid oxidase in Oculogyric Crisis

Question 34

The fatty liver in children with kwashiorkor is the result of this abnormality

Answer 34

Lack of substrates for protein synthesis in the liver.