It is often necessary to know the concentration of Chlamydomonas for culturing a
ID: 148599 • Letter: I
Question
It is often necessary to know the concentration of Chlamydomonas for culturing and experiments. There are two major ways to determine the concentration; using a hemocytometer and determining the OD of the culture with a spectrophotometer. Refer to the handout on blackboard to help with the following:
a (5 points). How much Chlamydomonas do you have (in cells/ml) if you have the found the following numbers when counting 5 “4x4” square sections (each 4x4 large square holds 0.004 ml volume) on a hemocytometer of a 1:10 dilution of your chlamy stock: 100, 120, 150, 168, 175?
b (5 points). How much Chlamydomonas do you have (in cells/ml) if you have the determined that a 1:10 dilution of your stock had an OD = 0.65?
Explanation / Answer
a (5 points). How much Chlamydomonas do you have (in cells/ml) if you have the found the following numbers when counting 5 “4x4” square sections (each 4x4 large square holds 0.004 ml volume) on a hemocytometer of a 1:10 dilution of your chlamy stock: 100, 120, 150, 168, 175?
Cells/mL= (sum of cells)/4 x dilution factor x 10^4
= (100+120+150+168+175)/4
=178.25 x 10 x 10^4
=178.25 x 10^5 cell/mL
b (5 points). How much Chlamydomonas do you have (in cells/ml) if you have the determined that a 1:10 dilution of your stock had an OD = 0.65?
Chlamydomonas concentration= OD750-0.088/(9 × 10^8)
=0.65-0.088/(9 ×10^8)
= 0.65 - 0.00977 x 10^8
=9.76 x 10^5 cell/mL
Dilution factor 10
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