Question 42 – Analysis - OCR A A Level Biology Questions

Scientists wanted to estimate the number of bacterial cells in a $cm345\text{ cm}^3$ suspension of Lactobacillus acidophilus. They carried out the following two serial dilutions:

$cm31\text{ cm}^3$ of the original suspension was mixed with $cm39\text{ cm}^3$ of sterile nutrient broth to make Solution 2.
$cm31\text{ cm}^3$ of Solution 2 was mixed with $cm39\text{ cm}^3$ of sterile nutrient broth to make Solution 3.

The scientists transferred $cm30.2\text{ cm}^3$ of Solution 3 onto an agar plate. After incubation, $33$ separate bacterial colonies grew on the plate.

Calculate the number of bacterial cells in the original $cm345\text{ cm}^3$ suspension.

Express your answer in standard form to three significant figures. Show your working.

Scientists wanted to estimate the number of bacterial cells in a $cm345\text{ cm}^3$ suspension of Lactobacillus acidophilus. They carried out the following two serial dilutions:

$cm31\text{ cm}^3$ of the original suspension was mixed with $cm39\text{ cm}^3$ of sterile nutrient broth to make Solution 2.
$cm31\text{ cm}^3$ of Solution 2 was mixed with $cm39\text{ cm}^3$ of sterile nutrient broth to make Solution 3.

The scientists transferred $cm30.2\text{ cm}^3$ of Solution 3 onto an agar plate. After incubation, $33$ separate bacterial colonies grew on the plate.

Calculate the number of bacterial cells in the original $cm345\text{ cm}^3$ suspension.

Express your answer in standard form to three significant figures. Show your working.

Analysis

Question 29

Analysis

Question 29

Analysis

Question 29

Analysis Questions

Analysis

Question 29

Analysis Questions