Microbio help please!

Question

What is the total surface area of a 50 mL Streptococcus pneumoniae culture at 5x10⁸ cells mL^-1 in which the cells have a radius of 0.5 mm? Calculate you answer in cm².



Answer 1

Hi Alicia,

The total surface area is 196349540.849 cm². Please check below to see how I came up with the answer.

-First, multiple the number of cells in 1 mL of culture by 50 as you are asked to calculate the total surface area of 50 mL of bacterial culture. So, 5x10⁸ cells x 50 = 25,000,000,000 cells.

-Next calculate the surface area of an individual cell using the equation for the surface area of a circle (πr²). So, π x 0.5² = 0.78539816339 mm².

-Then, multiply the total surface area of one cell by the total number of cells in a 50 mL culture. 0.78539816339 x 25,000,000,000 = 19634954084.9mm².

-Now that you have the total surface area for the 50 mL culture in mm² you can convert this number to cm² by dividing the mm² answer by 100 since 1 mm is 10 times smaller than 1 cm and you square the 10 (i.e. 10 x 10 = 100). So, 19634954084.9/100 = 196349540.849 cm².