Respiration experiments Flashcards
what are respirometers used for
to determine rate of aerobic respiration, by measuring the amount of oxygen consumed by an organism over a period of time.
for the woodlice respirometer practical: why is there potassium hydroxide in each tube
to absorb CO2
for the woodlice respirometer practical: what are the two types of test tubes
1) Test tube
2) Control tube- uses glass beads (same mass) instead of wood lice
- the control tube is to make sure results are only due to the woodlice respiring.
manometer
It is the capillary tube, with coloured fluid and a scale.
- coloured fluid is added by dipping the end of the capillary tube into a beaker of fluid.
capillary action makes the fluid move into the tube,
in which the syringe then sets the fluid to a known level.
why is there a decrease in volume of air of the test tube, and what does this cause to happen?
Due to oxygen consumption of the woodlice
- Decrease in the volume of air in the test tube, will reduce the pressure in the test tube, and cause the fluid in the manometer to move towards the test tube .
How to calculate the volume of oxygen taken in by the woodlice per minute?
work out distance moved by the liquid over a certain period of time ( eg 1 minute)
- you need to know the diameter of the capillary tube to do this.
examples of control variables ( woodlice experiment)
temperature, volume of potassium hydroxide, time ( e.g 20 minutes)
how do we make the experiment more reliable?
repeat the experiment and calculate a mean volume of oxygen taken in.
what can be used to measure the oxygen concentration in a respirometer chamber
by setting respirometers up with electronic oxygen sensors, that measure oxygen concentration at set intervals.
- data is automatically recorded to a data longer
reduces the chance of human error.
