The effect of different substrates on cellular respiration in yeast: practical

Key learning points

• Living yeast cells immobilised in alginate beads will carry out cellular respiration and produce carbon dioxide gas.
• The gas can be collected and the volume of gas measured using an upturned measuring cylinder under water.
• Identifying independent and dependent variables, and variables to control to increase the validity of the results.
• How to read the volume of gas from the meniscus in the measuring cylinder after a set time.
• Collecting repeat measurements for each substrate, and collecting data for different substrates.

Keywords

cellular respiration

An exothermic chemical process that transfers energy for life processes, using glucose as fuel.

independent variable

The factor that we change in an experiment.

dependent variable

The factor that we measure in an experiment.

random error

Causes results to differ by different amounts due to a factor other than the independent variable (the factor we changed).

systematic error

Causes measurements to differ from the true value by the same amount each time they are taken.

Common mistakes

• Pupils often read the volume of gas incorrectly as they do not measure it from the bottom of the meniscus of the water in the measuring cylinder.

  This lesson contains a detailed explanation of how to correctly measure volumes from the meniscus, and why this is important.