Culturing microorganisms and measuring growth Quiz
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5 questions, one answer each
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1. A 10⁻⁵ dilution plate (0.1 cm³ spread) has 36 colonies. How many viable cells are there per cm³ of the original culture?
- A. 3.6 × 10⁶
- B. 3.6 × 10⁷
- C. 3.6 × 10⁵
- D. 3.6 × 10⁴
2. Why is a plate with 800 colonies unsuitable for a viable count?
- A. Too few cells
- B. Colonies merge so they cannot be counted accurately
- C. The agar has dried
- D. The cells are dead
3. In which phase of the growth curve is the rate of cell division at its maximum and constant?
- A. Lag phase
- B. Exponential phase
- C. Stationary phase
- D. Death phase
4. A culture increases from 2 × 10³ to 1.28 × 10⁵ cells cm⁻³ in 3 hours of exponential growth. What is k?
- A. 1 per hour
- B. 3 per hour
- C. 2 per hour
- D. 6 per hour
5. Why can turbidity readings overestimate the number of living cells?
- A. Colorimeters are inaccurate
- B. Dead cells also scatter light
- C. Living cells absorb no light
- D. The blank is too clear