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Biochemistry Exam 5- 2nd Year- PMU

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Biochemistry Exam 5- 2nd Year-2nd Semester- PMU

Question 1 of 45

1

Which of the following is true?

Select one or more of the following:

  • Transaminases are specific for only one pair of α-amino and α-keto acids

  • Transaminases co-work with Vitamin B1 (thiamine pyrophosphate) as coenzyme

  • Transaminases co-work with Vitamin B6 (pyridoxal phosphate) as coenzyme

  • Transaminases fix ammonia as amino group in amino acids

  • Transaminases release free ammonia from α-amino acids

Explanation

Question 2 of 45

1

Which of the following a-amino acids is essential?

Select one or more of the following:

  • Glycine

  • Glutamate

  • Serine

  • Valine

  • Lysine

Explanation

Question 3 of 45

1

Which of the following α-amino acids are glycogenic?

Select one or more of the following:

  • Lysine, Cysteine and Proline

  • Glycine, Alanine and Proline

  • Leucine, lsoleucine and Valine

  • Aspartate, Glutamate and Serine

  • Leucine, Phenylalanine and Tyrosine

Explanation

Question 4 of 45

1

Which of the following α-amino acids is ketogenic?

Select one or more of the following:

  • Glycine

  • Leucine

  • lsoleucine

  • Valine

  • Alanine

Explanation

Question 5 of 45

1

Which of the following mechanisms play role in ammonia detoxification:

Select one or more of the following:

  • Glutamine biosynthesis in brain

  • Urea biosynthesis in muscles

  • Alanine biosynthesis in muscles

  • Urea biosynthesis in liver

  • NH4+ formation in kidney

Explanation

Question 6 of 45

1

Which of the following statements about glutamate dehydrogenase are true:

Select one or more of the following:

  • the enzyme is regulated

  • the enzyme is associated with the respiratory chain and the formation of energy

  • the enzyme uses FAD as cofactor

  • the enzyme uses NAD+ as cofactor

Explanation

Question 7 of 45

1

Which of the following statements about the urea cycle are true

Select one or more of the following:

  • urea catabolizes in urea cycle

  • it does not use cell energy

  • it has mitochondrial and cytosol phase

  • in urea cycle a toxic product is converted into less toxic product which is excreted

Explanation

Question 8 of 45

1

Which of the following is involved in purine ring formation?

Select one or more of the following:

  • Alanine

  • Aspartate

  • Glutamate

  • Carbamoyl phosphate

  • Glycine

Explanation

Question 9 of 45

1

Which of the following is involved in pyrimidine ring formation?

Select one or more of the following:

  • Alanine

  • Aspartate

  • Glutamate

  • Carbamoyl phosphate

  • Glycine

Explanation

Question 10 of 45

1

Which of the following about GOUT is TRUE:

Select one or more of the following:

  • it is characterised by elevated concentration of uric acid in blood

  • it may be due to overproduction of purine nucleotides or decreased renal excretion of uric acid

  • many of the clinical symptoms arise because of the high solubility of uric acid in the aqueous environment

  • allopurinol is used for the treatment of gout since it inhibits xanthine oxidase

Explanation

Question 11 of 45

1

Which are the end products from pyrimidine degradation

Select one or more of the following:

  • uric acid

  • β-aminoisobutyrate

  • urea

  • β-alanine

  • NH3 and CO2

Explanation

Question 12 of 45

1

Porphyrin biosynthesis occurs in:

Select one or more of the following:

  • cytosol

  • mitochondria

  • both cytosol and mitochondria

  • cytosol, mitochondria and cell nucleus

  • endoplasmic reticulum

Explanation

Question 13 of 45

1

Which of the following is correct?

Select one or more of the following:

  • heme is synthesized from succinyl-CoA and glycine

  • heme is synthesized from aspartate and carbamoyl phosphate

  • heme is an example of iron porphyrins

  • heme is an example of magnesium porphyrins

  • the clinical condition jaundice is due to elevation of bilirubin in blood plasma

Explanation

Question 14 of 45

1

Which of the following is TRUE:

Select one or more of the following:

  • in prehepatic jaundice only the direct bilirubin is increased in serum

  • in hepatic jaundice only the indirect bilirubin is increased in serum

  • in posthepatic (obstructive) jaundice urine urobilinogen is absent

  • the neonatal physiologic jaundice results from an accelerated hemolysis around the time of birth and an immature hepatic system for the uptake, conjugation and excretion of bilirubin

  • Gilbert Syndrome is caused by deficiency in biliverdin reductase

Explanation

Question 15 of 45

1

Which of the following is true?

Select one or more of the following:

  • Carbamoyl phosphate synthetase 1 uses glutamine for the synthesis of urea

  • NH3 may be toxic to the brain because ammonia reacts with α-ketoglutarate to form glutamate and this results in depletion of the levels of α-ketoglutarate which impairs the function of the TCA cycle in neurons

  • clinical symptoms of ammonia intoxication include tremor, slurred speech, blurred vision, coma and ultimately death

  • a high protein diet and starvation result in induction of urea cycle enzymes

Explanation

Question 16 of 45

1

Which of the following human proteins contain porphyrins:

Select one or more of the following:

  • Myoglobin

  • Cyt. P450

  • Cyt. C1

  • Catalase

  • Ferritin

Explanation

Question 17 of 45

1

Which of the following is NOT TRUE

Select one or more of the following:

  • Thymidylate synthase catalyzes the synthesis of dTMP

  • H4 folate derivatives serve as one carbon donor for purine biosynthesis de novo

  • ribonucleotide reductase plays important role in RNA synthesis

  • CTP is produced by amination of UTP by CTP synthetase

Explanation

Question 18 of 45

1

Which of the following amino acids may undergo oxidative deamination followed by energy production:

Select one or more of the following:

  • Glycine

  • Trytophan

  • Lysine

  • Glutamate

  • Cytesine

Explanation

Question 19 of 45

1

Which of the statements about aminotransferases are TRUE

Select one or more of the following:

  • they use thiamine diphosphate as a coenzyme

  • they use pyridoxal phosphate as a coenzyme

  • the ALAT content increases in cardiac infarction

  • the ASAT and ALAT content increases in liver disease (e.g: hepatitis)

Explanation

Question 20 of 45

1

Which of the following compounds can accept NH2-group in transamination

Select one or more of the following:

  • pyruvate

  • acetone

  • α-ketoglutarate

  • acetoacetate

  • oxaloacetate

Explanation

Question 21 of 45

1

Which of the following biogenicamines are neurotransmitters

Select one or more of the following:

  • γ-aminobutyrate (GABA)

  • serotonin

  • tyrosine

  • dopamine

  • adrenaline

Explanation

Question 22 of 45

1

Which of the following amino acids can not undergo transamination

Select one or more of the following:

  • lysine

  • proline

  • alanine

  • glutamate

  • threonine

Explanation

Question 23 of 45

1

Which of the statements about aminotransferase are TRUE

Select one or more of the following:

  • they use NAD + as a coenzyme

  • they use pyridoxal phosphate as a coenzyme

  • the ASAT content increases in cardiac infarction

  • the ASAT and ALAT content decreases in liver disease (e.g hepatitis)

Explanation

Question 24 of 45

1

Which of the following is TRUE

Select one or more of the following:

  • arginine and glycine are used for the biosynthesis of creatine

  • creatine phospate serves a storage form of energy in muscles, heart and brain

  • creatine kinase catalyses the reaction creatine phosphate -> creatinine

  • when ATP is utilized as a source of energy for muscular contraction creatine phosphate maintains its concentration

Explanation

Question 25 of 45

1

Which of the following compounds are neurotransmitters

Select one or more of the following:

  • serine

  • glycine

  • serotonin

  • dopamine

  • acetylcholine

Explanation

Question 26 of 45

1

Which of the following compounds are amino group acceptors in transaminase reactions?

Select one or more of the following:

  • α-ketoglutarate

  • acetone

  • oxaloacetate

  • pyruvate

  • glutamate

Explanation

Question 27 of 45

1

Which are the end products of N-metabolism?

Select one or more of the following:

  • Creatine

  • Creatinine

  • Urea

  • Ammonia

  • Ammonium cations

  • Uric acids

Explanation

Question 28 of 45

1

Which of the following statements about pyrimidine synthesis are TRUE:

Select one or more of the following:

  • Pyrimidine ring is formed by adding atoms to PRPP

  • PRPP is added to the already formed pyrimidine ring

  • Derivatives of tetrahydrofolate (THF) are necessary for TMP production

  • SAM is necessary for TMP production

Explanation

Question 29 of 45

1

What is the origin of the atoms for "de novo" purine synthesis?

Select one or more of the following:

  • N7, C8 and N9 from glycine

  • C4, C5 and N7 from glycine

  • C6 from CO2

  • C8 from CO2

Explanation

Question 30 of 45

1

Which of the following statements about iron metabolism are FALSE:

Select one or more of the following:

  • hemosiderin is the major iron-storage protein

  • ferritin is the major iron-storage protein

  • transrefin can bind only ferrous cations ( Fe3+)

  • transrefin can bind only ferrous cations ( Fe2+)

  • the major regulator of piasma iron concentration is the humoral factor hepcidin

Explanation

Question 31 of 45

1

Which of the following compounds participate in both Krebs cycle and in transaminase reactions?

Select one or more of the following:

  • oxaloacetate

  • acetoacetate

  • α-ketoglutarate

  • pyruvate

  • isocitrate

  • malate

Explanation

Question 32 of 45

1

N-atom in carbamoyl phosphate, used for pyrimidine ring synthesis, derives from

Select one or more of the following:

  • Ammonia (NH3)

  • Aspartate

  • Glutamate

  • Glutamine

  • Glycine

Explanation

Question 33 of 45

1

Which of the following reactions from urea cycle demand ATP?

Select one or more of the following:

  • Arginine -> Ornithine + Urea

  • Ornithine + Carbamoyl phosphate -> Citrulline

  • NH3 + CO2 -> Carbamoyl phosphate

  • Citrulline + Aspartate -> Arginosuccinate

  • Argininosuccinate -> Arginine + Fumarate

Explanation

Question 34 of 45

1

Which of the following statements about phenylalanine degradation are TRUE?

Select one or more of the following:

  • phenylalanine is hydroxylated to tyrosine

  • phenylalanine hydroxylases uses NADPH + H+ as a cofactor

  • a deficiency of homogentisate oxidase cause tyrosinemia type 2

  • a deficiency of phenyalanine hydroxylase results in higher concentration of phenylpyruvate, phenylpyruvate, phenyllactate and phenylacetate

  • phenylalanine hydroxylase uses ascorbic acid as a cofactor

Explanation

Question 35 of 45

1

Which of the following statements about "de novo“ purine synthesis are TRUE?

Select one or more of the following:

  • Purine ring formed by adding atoms to PRPP

  • PRPP to the already formed purine ring

  • Derivatives Of tetrahydrofolate (THF) are necessary for purine synthesis

  • SAM is necessary for purine synthesis

Explanation

Question 36 of 45

1

What of the following statements about iron metabolism are FALSE?

Select one or more of the following:

  • hephaestin and ceruloplasmln are both ferrireductases, but with different localization

  • hepcidin decreases serum iron by blocking ferroportin (IREG1)

  • the major iron depot is the hemosiderin in liver

  • transferrin is a non-heme iron-transport protein

Explanation

Question 37 of 45

1

Which of the following statements are TRUE?

Select one or more of the following:

  • normally urine does not contain urobilinogen

  • heme oxygenase requires NADH+H+ as a cofactor

  • in prehepatic jaundice (hemolytic anemia) there is an increase of urine urobilinogen

  • hepatic (parenchymal) jaundice is characterized by increase only of indirect bilirubin

  • posthepatic (obstructive) jaundice is characterized by an increase in direct bilirubin and pale feces

Explanation

Question 38 of 45

1

Which of the following amino acids are essential and glucogenic?

Select one or more of the following:

  • methionine

  • cysteine

  • phenylalanine

  • valine

  • threonine

  • tryptophan

Explanation

Question 39 of 45

1

Which of the following biologically active compounds DO NOT derive from tyrosine?

Select one or more of the following:

  • Dopamine

  • Melanin

  • Melatonin

  • GABA

  • Epinephrine

Explanation

Question 40 of 45

1

Which of the following statements about heme (haem) synthesis are TRUE:

Select one or more of the following:

  • it is located in the mitochondria

  • it is located in both the mitochondria and the cytosol

  • the main regulatory enzyme is ALA synthase

  • the main regulatory enzyme is ALA dehydratase

  • porphyrias can be caused by a deficiency in ALA syntahse

  • heme is the major allosteric inhibitor and gene suppresor synthesis

Explanation

Question 41 of 45

1

Which of the listed biologically active compounds derive from essential and semi-essential amino acids?

Select one or more of the following:

  • NO

  • GABA

  • Histamine

  • Melanin

  • Thyroid hormones

  • Melatonin

Explanation

Question 42 of 45

1

Which of the following statements about purines are FALSE:

Select one or more of the following:

  • The major regulatory enzyme of "de novo" purine synthesis is ALA synthetase

  • The major regulatory enzyme of ”de novo” purine synthesis is Glutamine-PRPP amidotransferase

  • There is a cross regulation between adenosine and guanosine nucleotides production

  • PRPP is the major allosteric inhibitor of ”de novo” purine synthesis

  • Gout can be caused by decreased activity of PRPP synthetase and increased activity of hypoxanthine-guanine phosphoribosyltransferase (HPGT)

Explanation

Question 43 of 45

1

Which of the following statements are TRUE

Select one or more of the following:

  • normally urine does not contain bilirubin

  • bilverdin reductase converts the green pigment biliverdin into direct bilirubin using NADPH + H+ as a cofactor

  • in prehepatic jaundice (hemolytic) there are only traces of urobililinogen in urine

  • hepatic (parenchymal) jaundice is characterized by an increase in urine urobilinogen

  • posthepatic (obstructive) jaundice is characterized by an increase in direct bilirubin and dark feces

  • bilirubin-UDP glucuronosyltransferase is deficient in Gilbert's syndrome

Explanation

Question 44 of 45

1

Which of the following is TRUE

Select one or more of the following:

  • carbamoyl phosphate synthetase 1 is a cytosolic enzyme

  • carbamoyl phosphate synthetase 1 is a mitochondrial enzyme

  • carbamoyl phosphate synthetase 1 uses glutamine as nitrogen donor

  • carbamoyl phosphate synthetase 1 is activated by N-acetyl glutamate

Explanation

Question 45 of 45

1

Which of the following human proteins contain porphyrins

Select one or more of the following:

  • the respiaratory chain cytochromes

  • cyt P450

  • hemoglobin

  • catalase

  • albumin

Explanation

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