Description : For Catecholamine biosynthesis the rate limiting enzyme is (A) DOPA decarboxylase (B) DOPAMINE β-hydroxylase (C) Tyrosine hydroxylase (D) Phenylalanine hydroxylase
Last Answer : Answer : C
Description : The rate limiting enzyme in the synthesis of catecholamines is: A. Tyrosine hydroxylase B. Dopa decarboxylase C. Dopamine β-hydroxylase D. Noradrenaline N-methyl transferase
Last Answer : A. Tyrosine hydroxylase
Description : The rate limiting step in catecholamine synthesis is catalysed by (A) Phenylalanine hydroxylase (B) Tyrosine hydroxylase (C) Dopa decarboxylase (D) Phenylethanolamine N-methyl transferase
Last Answer : Answer : B
Description : Tyrosine hydroxylase is inhibited by (A) Catecholamines (B) α−Methyldopa (C) Phenylalanine (D) Vanillyl mandelic acid
Last Answer : Answer : A
Description : All the following statements about phenylketonuria are correct except (A) Phenylalanine cannot be converted into tyrosine (B) Urinary excretion of phenylpyruvate and phenyllactate is increased (C) It ... diet (D) It leads to decreased synthesis of thyroid hormones, catecholamines and melanin
Last Answer : Answer : D
Description : The sequential steps in the conversion of tyrosine to epinephrine are (A) Ring hydroxylation-decarboxylation-side chain hydroxylation-N-methylation (B) Side chain hydroxylation-decarboxylation- ... chain hydroxylation-N-methylation (D) N-methylation-decarboxylation-ring and side chain hydroxylation
Description : A characteristic of pheochromocytoma is elevated urinary excretion of (A) Dopamine (B) Tyrosine (C) Vinylmandelic acid (D) Phenylalanine
Description : The limiting amino acid of rice is (A) Lysine (B) Tryptophan (C) Phenylalanine (D) Tyrosine
Description : True statements about the following neurotransmitters include: a. dopamine is formed from tyrosine b. in the synapse, noradrenaline is inactivated by active reuptake into the presynpatic terminals c. noradrenaline is formed by hydroxylation of dopamine d. all above
Last Answer : all above
Description : Epinephrine is derived from norepinephrine by (A) Decarboxylation (B) Hydroxylation (C) Oxidation (D) N-methylation
Description : In the biosynthesis of testosterone the rate limiting step is conversion of (A) Cholesterol to pregnenolone (B) Pregnenolone to progesterone (C) Progesterone to 17 α-hydroxy progesterone (D) 17 α-Hydroxy progesterone to androstenedione
Description : The principal rate limiting step in the biosynthesis of bile acids is at the (A) 7-Hydroxylase reaction (B) 12 α-Hydroxylase reaction (C) Conjugation reaction (D) Deconjugation reaction
Description : What is the rate-limiting-step in the cholesterol biosynthesis?
Last Answer : HMG CoA reductase.
Description : Dopamine is synthesised from (A) Dihydroxyphenylalanine (B) Epinephrine (C) Norepinephrine (D) Metanephrine
Description : Conversion of tyrosine to dihydroxyphenylalanine is catalysed by tyrosine hydroxylase which requires (A) NAD (B) FAD (C) ATP (D) Tetrahydrobiopterin
Description : The rage limiting step cholesterol biosynthesis is (A) Squalene synthetase (B) Mevalonate kinase (C) HMG CoA synthetase (D) HMG CoA reductase
Description : The rate limiting step in cholesterol biosynthesis is one of the followings : (A) LDL-receptor concentration (B) VLDL secretion (C) Mevalonic acid formation (D) Co-enzyme A formation
Last Answer : (C) Mevalonic acid formation
Description : Hydroxylation of phenylalanine requires all of the following except (A) Phenylalanine hydroxylase (B) Tetrahydrobiopterin (C) NADH (D) Molecular oxygen
Description : Biotin is involved in which of the following types of reactions? (A) Hydroxylation (B) Carboxylation (C) Decarboxylation (D) Deamination
Description : Vitamin B1 coenzyme (TPP) is involved in (A) Oxidative decarboxylation (B) Hydroxylation (C) Transamination (D) Carboxylation
Description : Histidine is converted into histamine by (A) Carboxylation (B) Decarboxylation (C) Methylation (D) Hydroxylation
Description : In the biosynthesis of cholesterol, the rate limiting enzyme is (A) Mevalonate kinase (B) HMG-CoA synthetase (C) HMG-CoA reductase (D) Cis-prenyl transferase
Last Answer : (A) Oxidative decarboxylation
Description : Melatonin is synthesised from (A) Phenylalanine (B) Tyrosine (C) Tryptophan (D) None of these
Description : Thyroid hormones are synthesized by the iodination of the amino acid: (A) Glycine (B) Phenylalanine (C) Alanine (D) Tyrosine
Description : Neonatal tyrosinemia is due to deficiency of the enzyme: (A) p-Hydroxyphenylpyruvate hydroxylase (B) Fumarylacetoacetate hydrolase (C) Phenylalanine hydroxylase (D) Tyrosine dehydrogenase
Description : Albinism is due to deficiency of the enzyme: (A) Phenylalanine hydroxylase (B) Tyrosinase (C) p-Hydroxyphenylpyruvic acid oxidase (D) Tyrosine dehydrogenase
Description : Activation or inactivation of certain key regulatory enzymes is accomplished by covalent modification of the amino acid: (A) Tyrosine (B) Phenylalanine (C) Lysine (D) Serine
Description : Niacin can be synthesised in human beings from (A) Histidine (B) Phenylalanine (C) Tyrosine (D) Tryptophan
Description : Richner-Hanhart syndrome is due to defect in (A) Tyrosinase (B) Phenylalanine hydroxylase (C) Hepatic tyrosine transaminase (D) Fumarylacetoacetate hydrolase
Description : Million’s test is positive for (A) Phenylalanine (B) Glycine (C) Tyrosine (D) Proline
Description : Which one of the following is an essential amino acid? (A) Arginine (B) Tyrosine (C) Phenylalanine (D) Proline
Description : Serotonin is synthesised from (A) Serine (B) Phenylalanine (C) Tyrosine (D) Tryptophan
Description : Million-Nasse’s reaction is specific for the amino acid: (A) Tryptophan (B) Tyrosine (C) Phenylalanine (D) Arginine
Description : Phenylalanine is the precursor of (A) L-DOPA (B) Histamine (C) Tyrosine (D) Throxine
Last Answer : C
Description : Which of the following amino acids produce a vasoconstrictor on decarboxylation? (A) Histidine (B) Tyrosine (C) Threonine (D) Arginine
Description : Formation of melanin from tyrosine requires the action of (A) Dopa decarboxylation (B) Diamine oxidase (C) Peroxidase (D) Tyrosinase
Description : The biosynthesis of both Catecholamine and serotonin require (A) Tyrosine hydroxylase (B) N-methyl transferase (C) Aromatic amino acid decarboxylase (D) Tryptophan pyrrolase
Description : In the synthetic pathway of epinephrine, disulfiram (antabuse) inhibits the enzyme: (A) Tyrosine hydroxylase (B) Dopamine β-hydroxylase (C) DOPA decarboxylase (D) N-methyl transferase
Description : In the biosynthesis of cholesterol, the step which controls the rate and locus of metabolic regulation is (A) Geranyl pyrophosphate farnesyl pyrophosphate (B) Squalene → lanosterol (C) HMG CoA → mevalonate (D) Lanosterol → 1, 4-desmethyl lanosterol
Description : .Khorana first deciphered the triplet codons of (a) serine and isoleucine (b) cysteine and valine (c) tyrosine and tryptophan (d) phenylalanine and methinonine.
Last Answer : (a) serine and isoleucine
Description : Khorana first deciphered the triplet codons of (a) serine and isoleucine (b) cysteine and valine (c) tyrosine and tryptophan (d) phenylalanine and methinonine
Last Answer : (b) cysteine and valine
Last Answer : (D) Tryptophan
Description : Following events occur in the cytoplasm and not inside storage vesicles, except (a) Conversion of tyrosine to dopa (b) Conversion of dopa to dopamine (c) Conversion of dopamine to norepinephrine (d) Conversion of dopamine to 3,4 dihydroxy phenyl acetic acid
Last Answer : Ans: C
Description : The following are true about the neurotransmitters: a. acetylcholine is inactivated mainly by presynaptic reuptake b. tyrosine is essential for the formation of dopamine c. noradrenaline is inactivated mainly by hydrolysis d. adrenaline is formed from methylation of the noradrenaline
Last Answer : adrenaline is formed from methylation of the noradrenaline
Description : Malic enzyme convers malic acid, in the presence of NADP+ to Pyruvic acid. This reaction is a/an (A) Decarboxylation (B) Decarboxylation and Dehydrogenation (C) Dehydrogenation (D) Oxidation
Description : Pantothenic acid is a constituent of coenzyme involved in (A) Acetylation (B) Decarboxylation (C) Dehydrogenation (D) Oxidation
Description : Pantothenic acid is a constituent of the coenzyme involved in (A) Decarboxylation (B) Dehydrogenation (C) Acetylation (D) Oxidation
Description : Biluveridin is converted to bilirubin by the process of (A) Oxidation (B) Reduction (C) Conjugation (D) Decarboxylation