Which of the following is true?
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
Which of the following a-amino acids is essential?
Glycine
Glutamate
Serine
Valine
Lysine
Which of the following α-amino acids are glycogenic?
Lysine, Cysteine and Proline
Glycine, Alanine and Proline
Leucine, lsoleucine and Valine
Aspartate, Glutamate and Serine
Leucine, Phenylalanine and Tyrosine
Which of the following α-amino acids is ketogenic?
Leucine
lsoleucine
Alanine
Which of the following mechanisms play role in ammonia detoxification:
Glutamine biosynthesis in brain
Urea biosynthesis in muscles
Alanine biosynthesis in muscles
Urea biosynthesis in liver
NH4+ formation in kidney
Which of the following statements about glutamate dehydrogenase are true:
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
Which of the following statements about the urea cycle are true
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
Which of the following is involved in purine ring formation?
Aspartate
Carbamoyl phosphate
Which of the following is involved in pyrimidine ring formation?
Which of the following about GOUT is TRUE:
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
Which are the end products from pyrimidine degradation
uric acid
β-aminoisobutyrate
urea
β-alanine
NH3 and CO2
Porphyrin biosynthesis occurs in:
cytosol
mitochondria
both cytosol and mitochondria
cytosol, mitochondria and cell nucleus
endoplasmic reticulum
Which of the following is correct?
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
Which of the following is TRUE:
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
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
Which of the following human proteins contain porphyrins:
Myoglobin
Cyt. P450
Cyt. C1
Catalase
Ferritin
Which of the following is NOT TRUE
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
Which of the following amino acids may undergo oxidative deamination followed by energy production:
Trytophan
Cytesine
Which of the statements about aminotransferases are TRUE
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)
Which of the following compounds can accept NH2-group in transamination
pyruvate
acetone
α-ketoglutarate
acetoacetate
oxaloacetate
Which of the following biogenicamines are neurotransmitters
γ-aminobutyrate (GABA)
serotonin
tyrosine
dopamine
adrenaline
Which of the following amino acids can not undergo transamination
lysine
proline
alanine
glutamate
threonine
Which of the statements about aminotransferase are TRUE
they use NAD + as a coenzyme
the ASAT content increases in cardiac infarction
the ASAT and ALAT content decreases in liver disease (e.g hepatitis)
Which of the following is TRUE
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
Which of the following compounds are neurotransmitters
serine
glycine
acetylcholine
Which of the following compounds are amino group acceptors in transaminase reactions?
Which are the end products of N-metabolism?
Creatine
Creatinine
Urea
Ammonia
Ammonium cations
Uric acids
Which of the following statements about pyrimidine synthesis are TRUE:
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
What is the origin of the atoms for "de novo" purine synthesis?
N7, C8 and N9 from glycine
C4, C5 and N7 from glycine
C6 from CO2
C8 from CO2
Which of the following statements about iron metabolism are FALSE:
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
Which of the following compounds participate in both Krebs cycle and in transaminase reactions?
isocitrate
malate
N-atom in carbamoyl phosphate, used for pyrimidine ring synthesis, derives from
Ammonia (NH3)
Glutamine
Which of the following reactions from urea cycle demand ATP?
Arginine -> Ornithine + Urea
Ornithine + Carbamoyl phosphate -> Citrulline
NH3 + CO2 -> Carbamoyl phosphate
Citrulline + Aspartate -> Arginosuccinate
Argininosuccinate -> Arginine + Fumarate
Which of the following statements about phenylalanine degradation are TRUE?
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
Which of the following statements about "de novo“ purine synthesis are TRUE?
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
What of the following statements about iron metabolism are FALSE?
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
Which of the following statements are TRUE?
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
Which of the following amino acids are essential and glucogenic?
methionine
cysteine
phenylalanine
valine
tryptophan
Which of the following biologically active compounds DO NOT derive from tyrosine?
Dopamine
Melanin
Melatonin
GABA
Epinephrine
Which of the following statements about heme (haem) synthesis are TRUE:
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
Which of the listed biologically active compounds derive from essential and semi-essential amino acids?
NO
Histamine
Thyroid hormones
Which of the following statements about purines are FALSE:
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)
Which of the following statements are TRUE
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
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
Which of the following human proteins contain porphyrins
the respiaratory chain cytochromes
cyt P450
hemoglobin
catalase
albumin
