题目

Assume that you have a culture of bacterial rods with dimensions 0.4 μm diameter by 1.2 μm length.The cells are 80 percent water,and 90 percent of dry weight is organic.Compute the volume and the organic mass of one cell.How many cells are present in one liter of culture if the organic dry weight (also called volatile suspended solids) is 100 mg/l?
书上原题就是如此。
如何计算？我问的不是如何翻译！

提问时间：2021-03-30

答案

题目中已经说了,细菌直径0.4微米,长1.2微米,杆状,因此可以容易用圆柱体公式算出体积是3.14×0.04×1.2≈0.15立方微米.然后题目告诉了,细胞中80%是水,然后18%是有机物,2%是其他物质,这里有一个近似,就是含有这么多水的细胞其密度基本与水相似.因此,一个细胞的有机物重量应该是0.15×18%=0.027=27纳克.然后要达到100mg/L的干重,则需要3.7×10^6个细胞/升