Measuring Growth by Direct Cell Counts quiz #1 Flashcards
Measuring Growth by Direct Cell Counts quiz #1
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Which of the following is NOT a direct method to measure microbial growth? Methods that do not directly count cells, such as measuring turbidity (optical density) or assessing metabolic activity, are NOT direct methods to measure microbial growth. Direct methods include direct microscopic cell counts, flow cytometers, and Coulter counters. A direct cell count determines the number of ______ in a sample. A direct cell count determines the number of total cells (including both viable and dead cells) in a sample. What is a major limitation of direct cell counting methods when determining cell numbers in a culture? Direct cell counting methods cannot distinguish between living (viable) and dead cells, so both are included in the total count. How does a gridded cover slip aid in direct microscopic cell counts? A gridded cover slip provides defined areas for counting, making it easier to count cells and calculate averages for cell concentration. Why is manual direct microscopic cell counting considered error-prone and time-consuming? Manual counting requires careful observation and tallying of cells in multiple grid areas, which can lead to mistakes and takes a long time. What is the principle behind cell detection in a flow cytometer? Cells pass through a narrow channel and a laser beam; the scattered light from each cell is detected and counted by the instrument. How does a Coulter counter differ from a flow cytometer in detecting cells? A Coulter counter detects cells electronically as they pass through a channel, rather than by measuring scattered light. What is the purpose of averaging cell counts from multiple grid areas in direct microscopic cell counting? Averaging counts from multiple grid areas helps provide a more accurate estimate of the number of cells per volume in the sample. What type of microscope is typically used for direct microscopic cell counts? A compound light microscope is commonly used for direct microscopic cell counts. Why might a scientist choose a direct cell counting method even if it includes dead cells? In some cases, knowing the total number of cells, regardless of viability, is sufficient for the scientist's research needs.
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