Description : Peptidyl transferase activity is present in (A) 40 S ribosomal subunit (B) 60 S ribosomal subunit (C) eEF-2 (D) Amino acyl tRNA
Last Answer : Answer : B
Description : Erythromycin acts on ribosomes and inhibit (A) Formation of initiation complex (B) Binding of aminoacyl tRNA (C) Peptidyl transferase activity (D) Translocation
Last Answer : Answer : D
Description : In prokaryotes, chloramphenicol (A) Causes premature release of the polypeptide chain (B) Causes misreading of the mRNA (C) Depolymerises DNA (D) Inhibits peptidyl transferase activity
Last Answer : Answer : A
Description : Peptidyl transferase activity of 50 S ribosomal subunits is inhibited by (A) Rifampicin (B) Cycloheximide (C) Chloramphenicol (D) Erythromycin
Last Answer : Answer : C
Description : Which of the following step of translation does not consume a high energy phosphate bond? (a) Peptidyl transferase reaction (b) Aminoacyl tRNA binding to A-site (c) Translocation (d) Amino acid activation
Last Answer : (b) Aminoacyl tRNA binding to A-site
Last Answer : (a) Peptidyl transferase reaction
Description : Streptomycin prevents synthesis of polypeptide by (A) Inhibiting initiation process (B) Releasing premature polypeptide (C) Inhibiting peptidyl transferase activity (D) Inhibiting translocation
Description : Peptidyl transferase activity is located in (A) Elongation factor (B) A charged tRNA molecule (C) Ribosomal protein (D) A soluble cytosolic protein
Description : The α-amino group of the new amino acyl tRNA in the A site carries out a nucleophilic attack on the esterified carboxyl group of the peptidyl tRNA occupying the P site. This reaction is catalysed by (A) DNA polymerase (B) RNA polymerase (C) Peptidyl transferase (D) DNA ligase
Description : The enzyme amino acyl tRNA synthetase is involved in (A) Dissociation of discharged tRNA from 80S ribosome (B) Charging of tRNA with specific amino acids (C) Termination of protein synthesis (D) Nucleophilic attack on esterified carboxyl group of peptidyl tRNA
Description : Select the antibiotic which inhibits bacterial protein synthesis by interfering with translocation of elongating peptide chain from acceptor site back to the peptidyl site of the ribosome so that ... chain is prematurely terminated: A. Chloramphenicol B. Erythromycin C. Tetracycline D. Streptomycin
Last Answer : B. Erythromycin
Description : eIF-1A and eIF-3 are required (A) For binding of amino acyl tRNA to 40 S ribosomal subunit (B) For binding of mRNA to 40 S ribosomal subunit (C) For binding of 60 S subunit to 40 S subunit (D) To prevent binding of 60 S subunit to 40 S subunit
Description : The mechanism of antibacterial action of tetracycline involves (a) Binding to a component of the 50S ribosomal subunit (b) Inhibition of translocase activity (c) Blockade of binding of ... (d) Selective inhibition of ribosomal peptidyl transferases (e) Inhibition of DNA-dependent RNA polymerase
Last Answer : Ans: C
Description : Translocation of the newly formed peptidyl tRNA at the A site into the empty P site involves (A) EF-II, GTP (B) EF-I, GTP (C) EF-I, GDP (D) Peptidyl transferase, GTP
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 : Binding of formylmehtionyl tRNA to 30 S ribosomal subunit of prokaryotes is inhibited by (A) Streptomycin (B) Chloramphenicol (C) Erythromycin (D) Mitomycin
Description : What is the action of tetracycline in prokaryotes? A- It blocks translocation reaction on ribosomes B- It blocks peptidyltransferase reaction on ribosomes C- It blocks the binding of amino-acyl tRNA to the A site of ribosomes D- Not known with certainity
Last Answer : It blocks the binding of amino-acyl tRNA to the A site of ribosomes
Description : Tetracyclines inhibit binding of amino acyl tRNAs to (A) 30 S ribosomal subunits (B) 40 S ribosomal subunits (C) 50 S ribosomal subunits (D) 60 S ribosomal subunits
Description : The first amino acyl tRNA approaches 40 S ribosomal subunit in association with (A) eIF-1A and GTP (B) eIF-2 and GTP (C) eIF-2C and GTP (D) eIF-3 and GTP
Description : Eukaryotic initiation factors 4A, 4B and 4F bind to (A) 40 S ribosomal subunit (B) 60 S ribosomal subunit (C) mRNA (D) Amino acyl tRNA
Description : In the process of elongation of chain binding of amino acyl tRNA to the A site requires (A) A proper codon recognition (B) GTP (C) EF-II (D) GDP
Description : The nucleophilic attack on the esterified carboxyl group of the peptidyl-tRNA occupying the P site and the α-amino group of the new amino acyl tRNA, the number of ATP required by the amino acid on the charged tRNA is (A) Zero (B) One (C) Two (D) Four
Description : Initiation of protein synthesis begins with binding of (A) 40S ribosomal unit on mRNA (B) 60S ribosomal unit (C) Charging of tRNA with specific amino acid (D) Attachment of aminoacyl tRNA on mRNA
Description : Antibacterial agents can be classified with regard to their structure, mechanism of action, and activity pattern against various types of bacterial pathogens. Which of the following ... are both bacteriostatic d. Sulfonamides and trimethoprim act synergistically to inhibit purine synthesis
Last Answer : Answer: a, b, d Penicillins, cephalosporins, and monobactams possess a b-lactam ring of some type and act to bind bacterial division plate proteins, thus inhibiting cell wall ... act in different mechanisms to inhibit protein synthesis, therefore two agents in combination act synergistically
Description : The newly entering amino acyl tRNA into A site requires (A) EF-II (B) Ribosomal RNA (C) mRNA (D) EF-I
Description : Puromycin causes premature chain termination in (A) Prokaryotes (B) Eukaryotes (C) Both (A) and (B) (D) None of these
Description : In eukaryotic cells (A) Formylated tRNA is important for initiation of translation (B) Cyclohexamide blocks elongation during translation (C) Cytosolic ribosomes are smaller than those found in prokaryotes (D) Erythromycin inhibits elongation during translation
Description : Chloramphenicol inhibits bacterial protein synthesis by: A. Binding to 30S ribosome and inhibiting attachment of aminoacyl tRNA B. Binding to 50S ribosome and preventing peptide bond formation C. Binding to ... chain D. Binding to both 30S and 50S ribosome and inducing misreading of mRNA code
Last Answer : B. Binding to 50S ribosome and preventing peptide bond formation
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 : Bacteria become erythromycin resistant by the following mechanisms except: A. Becoming less permeable to erythromycin B. Elaborating an erythromycin esterase enzyme C. Elaborating a protection ... the erythromycin binding site D. Altering the ribosomal binding site through a methylase enzyme
Last Answer : C. Elaborating a ‘protection protein’ which blocks the erythromycin binding site
Description : Which binding is inhibited by pactamycin? A- Aminoacyl-tRNA to the A-site of 30S subunit B- Initiator-tRNA to 30S/40S initiation complexes C- Peptidyl t-RNA to the 50S subunit D- Formation of peptide bond in P site
Last Answer : Initiator-tRNA to 30S/40S initiation complexes
Description : Insertion of a base in a gene can cause (A) Change in reading frame (B) Garbled amino acid sequence in the encoded protein (C) Premature termination of translation (D) All of these
Description : Which antibiotic inhibits interaction between tRNA and mRNA during bacterial protein synthesis? (a) Tetracycline (b) Erythromycin (c) Neomycin (d) Streptomycin
Last Answer : (d) Streptomycin
Description : .Which antibiotic inhibits interaction between tRNA and mRNA during bacterial protein synthesis? (a) Tetracycline (b) Erythromycin (c) Neomycin (d) Streptomycin
Last Answer : (c) Neomycin
Description : Insulin regulates fatty acid synthesis by (A) Dephosphorylating of acetyl CoA carboxylase (B) Activating phosphorylase (C) Inhibiting malonyl CoA formation (D) Controlling carnitine-Acyl CoA transferase activity
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 first amino acyl tRNA which initiates translation in prokaryotes is (A) Mehtionyl tRNA (B) Formylmethionyl tRNA (C) Tyrosinyl tRNA (D) Alanyl tRNA
Description : The first amino acyl tRNA which initiates translation in eukaryotes is (A) Mehtionyl tRNA (B) Formylmethionyl tRNA (C) Tyrosinyl tRNA (D) Alanyl tRNA
Description : All the following statements about charging of tRNA are correct except (A) It is catalysed by amino acyl tRNA synthetase (B) ATP is converted into ADP and Pi in this reaction (C) The enzyme recognizes the tRNA and the amino acid (D) There is a separate enzyme for each tRNA
Description : After formation of a peptide bond, mRNA is translocated along the ribosome by (A) eEF-1 and GTP (B) eEF-2 and GTP (C) Peptidyl transferase and GTP (D) Peptidyl transferase and ATP
Description : The primary mechanism underlying the resistance of gram-positive organisms to macrolide antibiotics is (a) Methylation of binding sites on the 50S ribosomal subunit (b) Formation of ... ) Formation of drug-inactivating acetyltranferases (e) Decreased drug permeability of the cytoplasmic membrane
Last Answer : Ans: A
Description : Mutations in promoter regions of genes can cause (A) Premature termination of translation (B) Change in reading frame of downstream structural gene (C) Decreased efficiency of transcription (D) All of these
Description : All of the following statements about nonsense codons are true except (A) They do not code for amino acids (B) They act as chain termination signals (C) They are identical in nuclear and mitochondrial DNA (D) They have no complementary anticodons
Description : The enzyme regulating extramitochondrial fatty acid synthesis is (A) Thioesterase (B) Acetyl CoA carboxylase (C) Acyl transferase (D) Multi-enzyme complex
Description : Synthesis of polyunsaturated fatty acids involves the enzyme systems: (A) Acyl transferase and hydratase (B) Desaturase and elongase (C) Ketoacyl-CoA reductase and hydratase (D) Dihydroxyacetone phosphate
Description : Acetyl-CoA is the principal building block of fatty acids. It is produced within the mitochondria and does not diffuse readily into cytosol. The availability of acetyl CoA involves (A) Carnitine acyl transferase (B) Pyruvate dehydrogenase (C) Citrate lyase (D) Thiolase
Description : Acetyl CoA required for extra mitochondrial fatty acid synthesis is produced by (A) Pyruvate dehydrogenase complex (B) Citrate lyase (C) Thiolase (D) Carnitine-acyl transferase
Description : LCAT is (A) Lactose choline alamine transferse (B) Lecithin cholesterol acyl transferase (C) Lecithin carnitine acyl transferase (D) Lanoleate carbamoyl acyl transferase
Description : Activated lecithin cholesterol acyl transferase is essential for the conversion of (A) VLDL remnants into LDL (B) Nascent HDL into HDL (C) HDL2 into HDL3 (D) HDL3 into HDL2