Biochemistry MCQ 373+

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• Which is the first reaction of the pentose phosphate pathway?
  ক

  Oxidation of glucose 6-phosphate to 6-phosphoglucono-δ-lactone

  খ

  Oxidation of 6-phosphogluconate to ketopentose ribulose 5-phosphate

  গ

  Reduction of 6-phosphoglucono-δ-lactone to glucose 6-phosphate

  ঘ

  Reduction of ketopentose ribulose 5-phosphate to 6-phosphogluconate
• Which product formed in the isomerization of mannose 6-phosphate?
  ক

  Fructose 6-phosphate

  খ

  Glucose 6-phosphate

  গ

  2-phosphoglycerate

  ঘ

  3-phosphoglycerate
• Site directed mutagenesis facilitated research on ____________
  ক

  Carbohydrates

  খ

  Proteins

  গ

  Lipids

  ঘ

  Fats
• The binding of ligands to many GPCRs leads to ____________
  ক

  Decrease in concentration of second messengers

  খ

  Increase in concentration of second messengers

  গ

  Decrease in concentration of first messengers

  ঘ

  Increase in concentration of first messengers
• In 3° structure of proteins, folding and shaping is done by ____________
  ক

  Hydrophobic interactions

  খ

  Polar interactions

  গ

  Hydrogen bonding

  ঘ

  None of the mentioned
• Tertiary conformation of proteins is maintained by 3 types of bonds namely ionic, hydrogen and ____________
  ক

  Sulfide

  খ

  Disulfide

  গ

  Covalent

  ঘ

  Peptide
• 1M NaCl and 1M HCl are present in an aqueous solution. What is the solution?
  ক

  Not a buffer solution with pH < 7

  খ

  Not a buffer solution with pH > 7

  গ

  A buffer solution with pH < 7

  ঘ

  A buffer solution with pH > 7
• If pH of solution of NaOH is 12.0 the pH of H2SO4 solution of same molarity will be ____________
  ক

  2.0

  খ

  12.0

  গ

  1.7

  ঘ

  10.0387
• Which of the following serves as a bactericidal agent?
  ক

  Ribonuclease

  খ

  Lysozyme

  গ

  Cytochrome c

  ঘ

  Myoglobin
• A structure that has hydrogen bonds between polypeptide chains arranged side by side is ____________
  ক

  Primary structure

  খ

  α-helix

  গ

  β-pleated sheets

  ঘ

  Tertiary structure
• Which of the following encodes recombinase?
  ক

  fliC

  খ

  fljB

  গ

  hin

  ঘ

  fljA
• When DNA segment is in one orientation ____________
  ক

  The gene for FljB and gene encoding FljA are expressed

  খ

  The gene for FliC are expressed

  গ

  The gene for FljB and gene encoding FljA are not expressed

  ঘ

  The gene for FljB and gene encoding FljC are not expressed
• Whose interaction with Lex-A facilitates the repressor’s self-cleavage reaction?
  ক

  Rec-A

  খ

  Rec-B

  গ

  Rec-C

  ঘ

  Rec-D
• Which of the following takes place when tryptophan levels are high?
  ক

  Attenuation at the attenuator structure formed by sequences of 3 and 4

  খ

  Ribosomes pauses at the Try codons in sequence 1

  গ

  Formation of paired structure between 2 and 3 sequences prevents attenuation

  ঘ

  2:3 structures, unlike the 3:4 attenuator, does not prevent transcription
• Which of the following takes place when tryptophan levels are low?
  ক

  Ribosomes quickly translates sequence 1

  খ

  Sequence 2 is blocked before sequence 3 is transcribed

  গ

  Ribosomes pauses at the Try codons in sequence 1

  ঘ

  Attenuation at the attenuator structure formed by sequences of 3 and 4
• Formation of the attenuator stem-and-loop structure depends on the events that occur during translation of ____________
  ক

  Regulatory sequence 1

  খ

  Regulatory sequence 2

  গ

  Regulatory sequence 3

  ঘ

  Regulatory sequence 4
• Attenuator sequences base-pair to form a stem-and-loop structure rich in ____________
  ক

  A = T

  খ

  G ≡ C

  গ

  A = C

  ঘ

  G = C
• Trp repressor is a ____________
  ক

  Homodimer

  খ

  Homotrimer

  গ

  Heterodimer

  ঘ

  Heterotrimer
• CAP is ____________
  ক

  Catabolite gene activator protein

  খ

  Catabolite gene repressor protein

  গ

  Anabolite gene activator protein

  ঘ

  Anabolite gene repressor protein
• Which of the following about mRNA stability is not correct?
  ক

  Regulation of mRNA stability is a way of regulating gene expression

  খ

  Prokaryotic mRNAs have a half-life of only a few minutes

  গ

  Histone mRNAs have especially long poly-A tails and are stable

  ঘ

  It is thought that poly-A tails stabilize eukaryotic mRNAs
• RNAi stands for ____________
  ক

  RNA inducer

  খ

  RNA interference

  গ

  RNA intron

  ঘ

  RNA insertion
• The mechanism by which CBP activates transcription is?
  ক

  CBP has DNA methyl transferase activity

  খ

  CBP has histone acetyl transferase activity

  গ

  CBP interacts with the basal transcription complex

  ঘ

  CBP interacts with the basal transcription complex and has histone acetyl transferase activity
• Which of the following increases gene expression as much as 200-fold?
  ক

  TATA box

  খ

  Insulator

  গ

  Enhancer

  ঘ

  CAAT box
• Which of the following statements regarding the regulation of trp operon expression by attenuation is correct?
  ক

  Rapid translation of the leader peptide prevents completion of mRNA transcript

  খ

  Rapid translation of the leader peptide allows completion of mRNA transcript

  গ

  The leader peptide sequence encodes enzymes required for tryptophan synthesis

  ঘ

  The leader peptide sequence contains no tryptophan residues
• Which of the following statements about lac operon in e.coli is true?
  ক

  Promoter is the binding site for the lac repressor

  খ

  Operon is only switched on in the absence of lactose in the growth medium

  গ

  β-galactosidase is only produced in large quantities when the lac repressor is bound to the operator

  ঘ

  Lac operon mRNA is a polycistronic mRNA
• To which class of transcription factor do nuclear receptors belong?
  ক

  Zinc finger proteins

  খ

  Leucine zipper proteins

  গ

  Helix-turn-helix proteins

  ঘ

  Helix-loop-helix proteins
• Which of the following is the most appropriate definition of an operator?
  ক

  A non-coding, regulatory DNA sequence that is bound by RNA polymerase

  খ

  A non-coding, regulatory DNA sequence that is bound by a repressor protein

  গ

  A DNA-binding protein that regulates gene expression

  ঘ

  A cluster of genes that are regulated by a single promoter
• Which out of the following is not an example of an inducible operon?
  ক

  Lactose operon

  খ

  Galactose operon

  গ

  Maltose operon

  ঘ

  Tryptophan operon
• Which of the following is not required for the expression of genes in the lactose operon?
  ক

  lacl gene product

  খ

  cAMP

  গ

  Allolactose

  ঘ

  Adenylate cyclase
• If lactose and glucose are provided in the growth medium of a culture of E. coli ____________
  ক

  Lactose operon is not transcribed

  খ

  Lactose metabolism is favored

  গ

  Both lactose and glucose are metabolized at same rate

  ঘ

  Adenylate cyclase is activated