Neco Model Questions Vol1 2025 Biology Question 44

Practice objective / multiple choice question 44 from the 2025 Neco Model Questions Vol1 Biology examination.

Neco Model Questions Vol1 2025 Biology Objective / Multiple Choice Hard Difficulty
Question 44 NECO_MODEL_QUESTIONS_VOL1 • 2025 • BIOLOGY • objective

A culture of *E. coli* is grown at 37 °C in nutrient broth. The initial viable cell count is \(2.0\times10^{4}\) CFU mL\(^{-1}\). The bacteria have a generation time of 20 min under these conditions. (a) How many viable cells will be present after 2 h? (b) After 1 h, an antibiotic is added that instantly reduces the viable cell count by 75 %. The surviving cells continue to divide with the same generation time. How many viable cells will be present 30 min after the antibiotic addition?

Answer Options

A. (a) \(1.10\times10^{6}\) CFU mL\(^{-1}\); (b) \(1.00\times10^{5}\) CFU mL\(^{-1}\) (approximately).
Correct Answer B. (a) \(1.28\times10^{6}\) CFU mL\(^{-1}\); (b) \(1.13\times10^{5}\) CFU mL\(^{-1}\) (approximately).
C. (a) \(1.35\times10^{6}\) CFU mL\(^{-1}\); (b) \(1.25\times10^{5}\) CFU mL\(^{-1}\) (approximately).
D. (a) \(1.20\times10^{6}\) CFU mL\(^{-1}\); (b) \(9.5\times10^{4}\) CFU mL\(^{-1}\) (approximately).
Correct Answer
B
Correct Option:
(a) \(1.28\times10^{6}\) CFU mL\(^{-1}\); (b) \(1.13\times10^{5}\) CFU mL\(^{-1}\) (approximately).

About This Question

This is Neco Model Questions Vol1 2025 Biology Question 44. It is one of the objective questions from the 2025 Neco Model Questions Vol1 Biology examination.

Difficulty level: Hard .

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