Description

The Perfect Brew was developed as part of an effort by the Quantitative Biology at Community Colleges group to provide materials that incorporate mathematical concepts into biology courses.   This activity highlights the use of concentration, dilution factors, and volume in the process of counting yeast cells on a hemocytometer.  This activity includes an instructor guide with answer key, assessment questions aligned with learning outcomes, and two student handouts.  

The student learning outcomes for this activity are:

1. Describe the purpose and use of a hemocytometer.
2. Describe and label the parts of a hemocytometer.
   1. describe the dimensions of the grid on the hemocytometer.
3. Describe how the volume of liquid on the cytometer relates to taking up space.
   1. describe the relationship between cubic millimeter and the microliter.
   2. describe the relationship between cubic centimeter and the milliliter (ml)
4. Describe how cells are visualized as dead or alive using Trypan blue.
   1. describe how cells exclude the dye from living cells and why they exclude. 
   2. consider the different cell shapes and healthiness of cells.
5. Describe and apply the rules of counting cells in a grid.
   1. count the cells in a given grid accurately.
   2. convert the cell count to a concentration.
   3. average the different counts from grids and determine a statistical mean.
   4. perform the calculations to determine the original concentration of cells in a sample. 
6. Describe the statistical rationale for the 30 to 300 rule. 

This material is based upon work supported by the National Science Foundation under Grant No. 1919613. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.

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