Description : An enzyme of pyrimidine nucleotide biosynthesis sensitive to allosteric regulation is (A) Aspartate transcarbamoylase (B) Dihydroorotase (C) Dihydroorotate dehydrogenase (D) Orotidylic acid decarboxylase
Last Answer : Answer : A
Description : An alternate substrate for orotate phosphoribosyl transferase is (A) Allopurinol (B) Xanthine (C) Hypoxanthine (D) Adenine
Last Answer : Answer : D
Description : Purine biosynthesis is inhibited by (A) Aminopterin (B) Tetracyclin (C) Methotrexate (D) Chloramphenicol
Description : The enzyme aspartate transcarbamoylase of pyrimidine biosynthesis is inhibited by (A) ATP (B) ADP (C) AMP (D) CTP
Description : An enzyme of pyrimidine nucleotides biosynthesis regulated at the genetic level by apparently coordinate repression and derepression is (A) Carbamoyl phosphate synthetase (B) Dihydroorotate dehydrogenase (C) Thymidine kinase (D) Deoxycytidine kinase
Description : Pyrimidine biosynthesis begins with the formation from glutamine, ATP and CO2, of (A) Carbamoyl aspartate (B) Orotate (C) Carbamoyl phosphate (D) Dihydroorotate
Last Answer : Answer : C
Description : Pyrimidine and purine nucleoside biosynthesis share a common precursor: (A) PRPP (B) Glycine (C) Fumarate (D) Alanine
Description : The major determinant of the overall rate of denovo purine nucleotide biosynthesis is the concentration of (A) 5-phosphoribosyl 1-pyrophosphate (B) 5-phospho β-D-ribosylamine (C) Glycinamide ribosyl-5-phosphate (D) Formylglycinamide ribosyl-5-phosphate
Description : The pathway of glycogen biosynthesis involves a special nucleotide of glucose. In the reaction below, NuDP stands for NuDP Glucose + glycogenn → NuDP + glycogenn+1 (A) ADP (B) GDP (C) UDP (D) CDP
Description : The first pyrimidine nucleotide to be formed in de novo synthesis pathway is (A) UMP (B) CMP (C) CTP (D) TMP
Description : Genetic code is (A) Collection of codon (B) Collection of amino acids (C) Collection of purine nucleotide (D) Collection of pyrimidine nucleotide
Description : The pyrimidine nucleotide acting as the high energy intermediate is (A) ATP (B) UTP (C) UDPG (D) CMP
Description : A pyrimidine nucleotide is (A) GMP (B) AMP (C) CMP (D) IMP
Description : A nucleotide consists of (A) A nitrogenous base like choline (B) Purine + pyrimidine base + sugar + phosphorous (C) Purine or pyrimidine base + sugar (D) Purine or pyrimidine base + phosphorous
Last Answer : Answer : B
Description : Tetracylin prevents synthesis of polypeptide by (A) Blocking mRNA formation from DNA (B) Releasing peptides from mRNA-tRNA complex (C) Competing with mRNA for ribosomal binding sites (D) Preventing binding of aminoacyl tRNA
Description : A nucleotide is formed of (a) purine, pyrimidine and phosphate (b) purine, sugar and phosphate (c) nitrogen base, sugar and phosphate (d) pyrimidine, sugar and phosphate
Last Answer : (c) nitrogen base, sugar and phosphate
Description : Adenine is (a) purine (b) pyrimidine (c) nucleoside (d) nucleotide.
Last Answer : (a) purine
Description : Which of the following nucleotide sequences contains 4 pyrimidine bases? (a) GATCAATGC (b) GCUAGACAA (c) UAGCGGUAA (d) Both (b) and (c)
Last Answer : a) GATCAATGC
Description : Uridine, present only in RNA is a (a) nucleoside (b) nucleotide (c) purine (d) pyrimidine.
Last Answer : a) nucleoside
Description : In the biosynthesis of cortiol, the sequence of enzymes involved is (A) Hydroxylase–dehydrogenase + isomerase – hydroxylase (B) Dehydrogenase–hydroxylase–isomerase (C) Hydroxylase–lyase–dehydrogenase isomerase (D) Isomerase–lyase–hydroxylase–dehydrogenase
Description : In biosynthesis of cholesterol triparanol inhibits the activity of the enzyme: (A) ∆24 Reductase (B) Oxidosqualene-lanosterol cyclase (C) Isomerase (D) Squalene epoxidase ENZYMES 155
Description : For biosynthesis of proteins (A) Amino acids only are required (B) Amino acids and nucleic acids only are required (C) Amino acid, nucleic acids and ATP only are required (D) Amino acids, nucleic acids, ATP, GTP, enzymes and activators are required
Description : All the enzymes required for de novo synthesis of pyrimidine nucleotides are cytosolic except (A) Carbamoyl phosphate synthetase (B) Aspartate transcarbamoylase (C) Dihydro-orotase (D) Dihydro-orotate dehydrogenase
Description : All of the following enzymes are unique to purine nucleotide synthesis except (A) PRPP synthetase (B) PRPP glutamyl amido transferase (C) Adenylosuccinate synthetase (D) IMP dehydrogenase
Description : Mature erythrocytes do not contain (A) Glycolytic enzymes(B) HMP shunt enzymes (C) Pyridine nucleotide(D) ATP
Last Answer : C
Description : Template/lock and key theory of enzyme action is supported by (A) Enzymes speed up reaction (B) Enzymes occur in living beings and speed up certain reactions (C) Enzymes determine the direction of reaction (D) Compounds similar to substrate inhibit enzyme activity
Description : Which one of the following statements is not characteristic of allosteric enzymes? (A) They frequently catalyze a committed step early in a metabolic pathway (B) They are often composed of subunits (C) They follow Michaelis-Menten kinetics (D) They frequently show cooperativity for substrate binding
Description : Enzymes activity is controlled by (A) pH of the solution (B) Temperature (C) Concentration of the enzyme (D) Concentration of the substrate (E) All of these
Description : If a coenzyme is required in an enzyme reaction, the former usually has the function of (A) Acting as an acceptor for one of the cleavage products of the substrate (B) Enhancing the specificity ... C) Increasing the number of receptor sites of the apo enzyme (D) Activating the substrate ENZYMES 167
Description : Which of the following enzymes incorporates inorganic phosphate into the substrate? (A) Phosphoglycerate kinase (B) Glyceraldehyde-3-phosphate dehydrogenase (C) Pyruvate kinase (D) Enolase
Description : Enzymes requiring NAD as co-substrate can be assayed by measuring change in absorbance at (A) 210 nm (B) 290 nm (C) 340 nm (D) 365 nm
Description : If all the enzymes, intermediates and cofactors of the citric acid cycle as well as an excess of the starting substrate acetylCoA are present and functional in an organelle free solution at the appropriate ... oxygen (B) Half life of enzyme (C) Turnover of intermediates (D) Reduction of cofactors
Description : Lineweaver – Burk double reciprocal plot is related to (A) Substrate concentration (B) Enzyme activity (C) Temperature (D) Both (A) and (B) ENZYMES 145
Description : The binding of prokaryotic DNA dependent RNA polymerase to promoter sits of genes is inhibited by the antibiotic: (A) Streptomycin (B) Rifamcin (C) Aueromycin (D) Puromycin
Description : The antibiotic which has a structure similar to the amino acyl end of tRNA tyrosine is (A) Actinomycin d (B) Streptomycin (C) Puromycin (D) Mitomycin c
Description : The antibiotic which cleaves DNA is (A) Actinomycin d (B) Streptomycin (C) Puromycin (D) Mitomycin C
Description : The antibiotic which inhibits DNA dependent RNA polymerase is (A) Mitomycin C (B) Actinomycin d (C) Streptomycin (D) Puromycin
Description : All of the following statements about puromycin are true except (A) It is an alanyl tRNA analogue (B) It causes premature termination of protein synthesis (C) It inhibits protein synthesis in prokaryotes (D) It inhibits protein synthesis in eukaryotes
Description : Puromycin causes premature chain termination in (A) Prokaryotes (B) Eukaryotes (C) Both (A) and (B) (D) None of these
Description : The binding of prokaryotic DNA dependent RNA polymerase to promoter sites of genes is inhibited by the antibiotic: (A) Puromycin (B) Rifamycin (C) Terramycin (D) Streptomycin
Description : The coupling of oxidation and phosphorylation in intact mitochondria: (A) Puromycin (B) Oligomycin (C) Streptomycin (D) Gentamycin
Description : Fatty liver may be caused by (A) Deficiency of methionine (B) Puromycin (C) Chronic alcoholism (D) All of these
Description : By which of the following means antifungal chemotherapeutic agents may affect fungi? A- Interfere with nuclear division by preventing the aggregation of microtubules needed for mitosis B- ... membrane-bound enzymes like thoseinvolved in nutrient transport and chitin synthesis D- all of these
Last Answer : all of these
Description : Restriction endonucleases are enzymes which (a) make cuts at specific positions within the DNA molecule (b) recognize a specific nucleotide sequence for binding of DNA ligase (c) restrict the action of the enzyme DNA polymerase (d) remove nucleotides from the ends of the DNA molecule
Last Answer : (a) make cuts at specific positions within the DNA molecule
Description : What is the role of NAD+ in cellular respiration ? (1) It functions as an enzymes (2) It functions as an electron carrier (3) It is a nucleotide source for ATP synthesis (4) It is the final electron acceptor for anaerobic respiration
Last Answer : (2) It functions as an electron carrier
Description : All of the following statements about allopurinol are true except (A) It is a structural analogue of uric acid (B) It can prevent uric acid stones in the kidneys (C) It increases the urinary excretion of xanthine and hypoxanthine (D) It is a competitive inhibitor of xanthine oxidase
Description : Carbonic anhydrase is competitively inhibited by (A) Allopurinol (B) Acetazolamide (C) Aminopterin (D) Neostigmine
Description : A drug which prevents uric acid synthesis by inhibiting the enzyme xanthine oxidase is (A) Aspirin (B) Allopurinol (C) Colchicine (D) Probenecid
Last Answer : B
Description : What characteristics of enzymes makes them specific for substrate?
Last Answer : shape of their active site make them specific for thesubstrates
Description : Why do we compare enzymes and substrate to a lock and key?
Last Answer : What is the answer ?