BSc Second Year (Sem 3 & 4) Microbiology – Daily Revision MCQ (English Medium)
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In Michaelis–Menten kinetics, Km is the substrate concentration at which the reaction velocity equals:
Chapter 1: Enzymes
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Answer: B. ½ Vmax
Putting v = Vmax/2 in v = Vmax[S]/(Km + [S]) gives [S] = Km.What is the net gain of ATP (by substrate-level phosphorylation) when one glucose molecule is broken to two pyruvate in glycolysis?
Chapter 2: Microbial Metabolism
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Answer: A. 2
Glycolysis makes 4 ATP but uses 2 ATP in the preparatory steps, so the net gain is 2 ATP per glucose.In SDS-PAGE, proteins are separated mainly on the basis of their:
Chapter 3: Bioanalytical Techniques: Chromatography, Electrophoresis and Centrifugation
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Answer: B. Molecular weight (size)
SDS coats proteins with a uniform negative charge per unit length, so migration through the gel depends mainly on size.The Meselson–Stahl experiment (using ¹⁵N and ¹⁴N) proved that DNA replication is:
Chapter 4: DNA Structure and Replication
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Answer: C. Semiconservative
After one generation in ¹⁴N all DNA was of hybrid density, showing each daughter molecule keeps one parental strand.Which of the following codons is NOT a stop (termination) codon?
Chapter 6: Genetic Code and Translation
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Answer: D. UGG
UAA, UAG and UGA are the three stop codons; UGG codes for tryptophan.In the lac operon of E. coli, the natural inducer that binds the repressor is:
Chapter 7: Regulation of Gene Expression: The Lac Operon
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Answer: B. Allolactose
Allolactose (an isomer of lactose) binds the lac repressor and releases it from the operator, allowing transcription.Which bacteriophage can follow the lysogenic cycle?
Chapter 11: Bacteriophages
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Answer: C. Lambda (λ)
Phage λ is a temperate phage that can integrate as a prophage; T-even phages and T7 are virulent (lytic only).Which class of antibody is a pentamer and is the first to appear in a primary immune response?
Chapter 13: Antigens and Antibodies
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Answer: A. IgM
IgM is secreted as a pentamer (with a J chain) and is the first antibody produced in a primary response.The tuberculin (Mantoux) skin reaction is an example of:
Chapter 15: Hypersensitivity Reactions
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Answer: D. Type IV hypersensitivity
It is a delayed-type reaction (48–72 h) mediated by sensitised T cells, i.e. Type IV, not antibodies.Penicillin kills bacteria by inhibiting:
Chapter 18: Antimicrobial Agents
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Answer: B. Cell wall (peptidoglycan) synthesis
Penicillin, a β-lactam, blocks the transpeptidation (cross-linking) step of peptidoglycan synthesis.
BSc Second Year (Sem 3 & 4): MCQ in other subjects
All questions are written by PadhaiNotes in our own words from the common syllabus of Maharashtra universities (NEP). Your own university's syllabus may differ a little.