Edexcel A-Level Biology B 9BI0
Biological Molecules
Cells, Viruses and Reproduction of Living Things
Classification and Biodiversity
Exchange and Transport
Energy for Biological Processes
Microbiology and Pathogens
Modern Genetics
Origins of Genetic Variation
Control Systems
Ecosystems
Energy for Biological Processes
Measuring respiration with a respirometer
- 2 things to know
- Papers 1 and 3
Overview
Recall questions on how a respirometer measures respiration, carbon dioxide absorbents, the control tube and equilibration, the variables to investigate and control, calculating rate from fluid movement, adapting it for anaerobic respiration, and the safe and ethical use of organisms.
What you need to know
Answer each one before you reveal it.
State one safety precaution when using potassium hydroxide in a respirometer experiment.
Questions from this subtopic
Each one with the model answer underneath.
- 1
What does a respirometer measure?
Model answer
The rate of respiration, by detecting changes in gas volume as oxygen is consumed or carbon dioxide is produced.
- 2
Why is a carbon dioxide absorbent used in a respirometer when investigating aerobic respiration?
Model answer
So that volume changes reflect only oxygen uptake.
- 3
Name two substances that can be used as carbon dioxide absorbents in a respirometer.
Model answer
Potassium hydroxide or soda lime.
- 4
When setting up a respirometer to measure aerobic respiration, what absorbent should be included and why?
Model answer
A carbon dioxide absorbent such as potassium hydroxide or soda lime, so that volume changes reflect only oxygen consumption.
- 5
State three factors that can be investigated using a respirometer.
Model answer
Temperature, substrate availability, and type of organism.
- 6
List four control variables that should be maintained in respirometer experiments.
Model answer
Temperature, volume of organisms, equilibration time, and ensuring the apparatus is airtight.
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