If urine sample darkens on standing, most likely diagnosis for patient is:

*A. Alkaptonuria

B. Phenylketonuria

C. Diabetes mellitus

D. Albinism

E. Maple syrup urine desease

Phenylketonuria is due to the absence of certain enzyme. Choose the reaction catalyzed by the enzyme:

A. Homogentisic acid oxidation

B. Tyrosine deamination

C. Tyrosine iodination

*D. Phenylalanine hydroxylation

E. Conversion of tyrosine to dihydroxyphenylalanine (DOPA)

One of hereinafter stated compounds forms a connecting link between urea cycle and Krebs cycle via oxaloacetate. Point out it:

A. Phenylalanine

B. Alanine

*C. Aspartate

D. Tryptophan

E. Glutamate

Albinism is due to the lack of special enzyme in melanocytes. Name it:

A. Homogentisate oxydase

B. Phenylalanine hydroxylase

C. Tyrosine decarboxylase

*D. Tyrosinase

E. Kynureninase

Which of the following functions is not specific for glutathione:

A. It protects a cell against cytotoxic H₂O₂ being coenzyme of glutathione peroxidase

B. It serves as coenzyme for certain enzymes e.g. prostaglandine PGE₂ synthase

*C. It serves as a storage and transport form of NH₃

D. It prevents the oxidation of sulfhydryl groups of several proteins to disulfide groups

E. It is involved in the transport of amino acids across cellular membrane in the intestine and kidney

Albinism is due to deficiency of the following enzyme:

A. Tyrosine transaminase

B. Phenylalanine hydroxylase

C. Tyrosine decarboxylase

D. Homohentisic acid oxidase

*E. Tyrosinase

Point out the pathology that is estimated in patients with genetic deficiency of dihydrobiopterin reductase:

A. Diabetes mellitus

B. Gout

C. Classic phenylketonuria

D. Ishemic heart disease

*E. Phenylketonuria type II

Choose the type of infringement in pathology named alkaptonuria:

A. The damage of receptor synthesis

B. The inhibition of amino acid formation

C. The viral damage of hepatocyte

*D. Genetic deficiency of enzyme

E. The renal insufficiency

Three biogenic amines are formed during the metabolism of tyrosine. Point out one of them:

A. Serotonin

B. Thiamine

*C. Adrenalin

D. Histamine

E. Thyroxin

The most direct precursor of taurine is:

A. Tyrosine

B. Glutathione

C. Glycine

D. Methionine

*E. Cysteine

N-acetylglutamate is activator for one enzyme involved in urea formation. Choose it:

A. Argino-succinate synthase

*B. Carbamoyl phosphate synthase I

C. Argino-succinase

D. Ornithine transcarbamoylase

E. Arginase

Name an amino acid which is precursor in the synthesis of some hormones in human body:

A. Alanine

*B. Tyrosine

C. Arginine

D. Serine

E. Lysine

Melanin may be synthesized from:

A. Tryptophan

*B. Phenylalanine

C. Serine

D. Cysteine

E. Methionine

A 4 y.o. boy has had recently serious viral hepatitis. Now there are such clinical symptoms as vomiting, unconsciousness, fits. There is hyperammoniemia in patient, too. Disturbance of which biochemical process caused such pathological condition of the patient?

A. Activation of amino acid decaboxylation

B. Inhibition of transamination enzymes

*C. Disturbed neutralization of ammonia in the liver

D. Increased putrefaction of proteins in bowels

E. Disturbed neutralization of biogenic amines

Citrullinemia accompanied with vomiting, mental retardation, convulsions. Which urea cycle enzyme hereditary defect is a cause of mentioned disturbances?

A. Carbamoyl phosphate synthase I

B. Arginosuccinase

C. Arginase

D. Ornithine transcarbamoylase

*E. Arginosuccinate synthase

Alkaptonuria is due to the deficiency of one enzyme in human tissues. Choose it

A. Tyrosinase

B. Phenylalanine hydroxylase

C. Dihydroxyphenylalanine (DOPA) decarboxylase

D. DOPA oxidase

*E. Homogentisate oxydase

After a serious viral infection a 3-year-old child has repeated vomiting, loss of consciousness, convulsions. Examination revealed hyperammoniemia. What may have caused changes of biochemical blood indexes of this child?

A. The increased putrefaction of proteins in intestines

B. Activated processes of amino acids decarboxylation

C. The inhibited activity of enzymes for transamination

D. Disorder of biogenic amines neutralization

*E. Disorder of ammonia neutralization in ornithine cycle

Choose the hormone that is formed from tryptophan:

*A. Melatonin

B. Thyroxin

C. Epinephrine

D. Histamine

E. Nor-epinephrine

Point out the coenzyme used for hydroxylases structure in phenylalanine and tyrosine conversions:

A. NADPH

B. Dihydrobiopterin

*C. Tetrahydrobiopterin

D. Biotin

E. FAD

Maple syrup urine disease is due to a defect in the enzyme complex which catalyzes oxidative decarboxylation reaction and is similar to any other alpha-keto acid dehydrogenase complexes in composition. Some patients who exhibit the symptoms of this disease respond to therapeutic doses of hereinafter stated vitamins. Point out it:

*A. Thiamine

B. Pyridoxine

C. Cobalamine

D. Biotin

E. Ascorbic acid

Cerebral trauma caused the increase of ammonia formation. What amino acid takes part in removal of ammonia from cerebral tissue?

A. Valine

*B. Glutamic acid

C. Tryptophan

D. Lysine

E. Туrosine

Nappies of a newborn have dark spots that witness the presence of homogentisic acid oxidation product. Choose the substance whose metabolic disorder is associated with accumulation of homogentisic acid in the organism:

A. Cholesterol

*B. Tyrosine

C. Galactose

D. Methionine

E. Tryptophan

The amino acids required for the formation of glutathione are:

A. Glutamate, aspartate, arginine

*B. Glycine, cysteine, glutamate

C. Valine, leucine, isoleicine

D. Cysteine, methionine, proline

E. Serine, Tyrosine, tryptophan

Glycine is used for synthesis of:

*A. All the proposed options are correct

B. Hemoglobin

C. Glutathione

D. Purine

E. Creatine

Try to choose the index of blood plasma used for estimation of liver function in utilization of ammonia:

A. Uric acid concentration

*B. Urea content

C. Glucose concentration

D. Pyruvic acid content

E. Ketone bodies content

Point out the pathologic state that may be estimated in patients with genetic defect of Phenylalanine -4-hydroxylase:

A. Hypercholesterinemia

*B. Aminoaciduria

C. Glucosemia

D. Dislipoproteinemia

E. Hyperuricemia

A 4 y.o. child with signs of durative proteinic starvation was admitted to the hospital. The signs were as follows: Growth inhibition, anemia, oedema, mental deficiency. Choose the cause of oedema development:

*A. Reduced synthesis of albumins

B. Reduced synthesis of globulins

C. Reduced synthesis of glycoproteins

D. Reduced synthesis of lipoproteins

E. Reduced synthesis of hemoglobin

Which of the following compounds is not a catabolic product of tryptophan?

A. Melatonin

B. Tryptamine

C. Serotonin

*D. Melanin

E. Kynurenine

Choose the blood plasma index that is used in screening of newborn for phenylketonuria estimation:

A. Pyruvate

B. Acetoacetate

*C. Phenylalanine

D. Uric acid

E. Dihydroxyphenylalanine

Which of the following statements is incorrect concerning synthesis of carbamoyl phosphate?

A. Two ATP may be consumed for its synthesis

B. This synthesis is catalyzed by carbamoyl phosphate synthases

*C. Mitochondrial carbamoyl phosphate synthase requires aspartate for its activity

D. It is the key reaction for urea formation

E. The nitrogen source can be either ammonia or glutamine

Albinos can't stand sun impact – they don't require sun-tan but get sunburns. Disturbed metabolism of what amino acid underlies this phenomenon?

A. Methionine

B. Glutamic acid

C. Tryptophan

D. Histidine

*E. Phenylalanine

Point out the cofactor required for the tyrosine formation from phenylalanine:

A. Coenzyme A

*B. Tetrahydrobiopterin

C. Lipoic acid

D. Tetrahydrofolate

E. Coenzyme Q

The major source of ammonia in the kidneys is:

A. Aspartate

B. Glutamate

*C. Glutamine

D. Urea

E. Histidine

Point out the index of the blood plasma that is used for the estimation of liver parenchyma damage:

*A. Urea

B. Glucose

C. Free amino acids

D. Ca²⁺

E. Cholesterol ester

Which of the following statements is incorrect concerning synthesis of carbamoyl phosphate?

A. It is the key reaction for urea formation

*B. This synthesis is catalyzed by ornithine transcarbamoylase

C. Two ATP may be consumed for its synthesis

D. It is mediated by different enzymes in the cytosol and mitochondria of the liver

E. The nitrogen source can be either ammonia or glutamine

A boy (of 10 years) complains of general weakness, dizziness, and tiredness. A mental retardation is observed. A concentration of valine, leucine, isoleucine is high in blood and urine. Urine has a specific odour. Name the probable diagnosis:

*A. Maple syrup urine disease

B. Histidinemia

C. Tyrosinemia

D. Basedow’s disease

E. Addison’s disease

Point out the enzyme whose deficiency causes the hyperammonemia state in patient:

A. L-Alanine oxidase

B. Pyruvate dehydrogenase

C. Aspartate transaminase

*D. Ornithine transcarbamoylase

E. Arginine transaminase

Find out the main important pathway for ammonia utilization in the brain:

A. Amino acid decarboxylation

*B. Urea formation

C. Conversion into glucose

D. Ammonia salts formation

E. Synthesis of glutamine from alpha-ketoglutarate

The brain ammonia isn’t neutralized through the formation of urea. Name the terminal product of ammonia neutralization in the brain:

A. Carbamoyl phosphate

B. Alanine

C. Urea

D. Aspartic acid

*E. Glutamine

Urea is produced by single enzyme. Point out it:

A. Uricase

B. Urease

C. Glutaminase

D. Carbamoyl phosphate synthetase

*E. Arginase

Maple syrup urine disease is due to deficiency of:

A. Decarboxylase

B. Dehydroxylase

C. Transaminase

*D. Alpha-keto acid dehydrogenase complex

E. Deaminase

The urine of patient with alkaptonuria contains:

A. None of the above

B. Phenylalanine

C. Acetates

*D. Homogentisic acid

E. Ketones

Point out the vitamin derivative that may be synthesized from tryptophan:

*A. NADH

B. FMN

C. FAD

D. CoASH

E. Carboxybiotin

Which one of the following amino acids can be converted to an intermediate of either the Krebs cycle or urea cycle?

A. Tyrosine

B. Tryptophan

C. Leucine

*D. Aspartate

E. Lysine