5A - Respiration experiments Flashcards
What can we investigate factors affecting respiration in?
Single-celled organisms.
What single celled organisms can we use to investigate factors affecting respiration? Why?
Yeast as they can be grown in culture, they can respire aerobically when plenty of oxygen is available and anaerobically when oxygen isn’t available.
What specifically can we measure from yeast to investigate factors affecting respiration?
The rate of CO2 production.
What is produced when yeast respires aerobically as well as when yeast respire anaerobically?
CO2
What method/equipment can be used to investigate factors affecting respiration in yeast?
A gas syringe (to collect the CO2).
Describe the method you would use to investigate factors affecting AEROBIC respiration in yeast? (Temperature)
1) Put a known volume and concentration of substrate solution (e.g. glucose) in a test tube. Add a known volume of buffer solution to keep the Ph constant.
2) Place the test tube in a water bath set to one of the temperatures being investigated. Leave it there for 10mins to allow the temperature of the substrate to stabilise.
3) Add a known mass of dried yeast (e.g. Saccharomyces cerevisiae) to the test tube and stir for 2mins.
4) After the yeast has dissolved into the solution, put a bung with a test tube attached to a gas syringe in the top of the test tube. The gas syringe should be set on zero.
5) Start a stopwatch as soon as the bung has been put in the test tube.
6) As the yeast respire, the CO2 formed will travel up the tube and into the gas syringe, which is used to measure the volume of CO2 released.
7) At regular time intervals (e.g. every minute), record the volume of CO2 that is present in the gas syringe. Do this for a set amount of time (e.g. 10mins)
8) A control experiment should also be set up at each temperature, where no yeast is present. No CO2 should be formed without the yeast.
9) Repeat the experiment 3 times at each temperature you’re investigating. Use your data to calculate the mean rate of CO2 production at each temperature (e.g. 10, 20 and 25 degrees).
Describe the method you would use to investigate factors affecting ANAEROBIC respiration in yeast? (Temperature)
1) Put a known volume and concentration of substrate solution (e.g. glucose) in a test tube. Add a known volume of buffer solution to keep the Ph constant.
2) Place the test tube in a water bath set to one of the temperatures being investigated. Leave it there for 10mins to allow the temperature of the substrate to stabilise.
3) Add a known mass of dried yeast (e.g. Saccharomyces cerevisiae) to the test tube and stir for 2mins.
4) After the yeast has dissolved into the substrate solution, trickle some liquid paraffin down the inside of the test tube so that it settles on and completely covers the surface of the solution. This will stop oxygen getting in, which will force the yeast to respire anaerobically.
5) Put a bung, with a test tube attached to a gas syringe, in the top of the test tube. The gas syringe should be set at zero.
6) Start a stopwatch as soon as the bung has been put in the test tube.
7) As the yeast respire, the CO2 formed will travel up the tube and into the gas syringe, which is used to measure the volume of CO2 released.
8) At regular time intervals (e.g. every minute), record the volume of CO2 that is present in the gas syringe. Do this for a set amount of time (e.g. 10mins)
9) A control experiment should also be set up at each temperature, where no yeast is present. No CO2 should be formed without the yeast.
10) Repeat the experiment 3 times at each temperature you’re investigating. Use your data to calculate the mean rate of CO2 production at each temperature (e.g. 10, 20 and 25 degrees).
What can the rate of oxygen consumption be measured using?
A respirometer.
What can respirometers be used to indicate?
The rate of aerobic respiration by measuring the amount of oxygen consumed by an organism over a period of time.
Explain how a respirometer can be used to measure the respiration of small organisms/plant seeds (using woodlice as an example)
1) Set up the apparatus partially submerged in a water bath at 15 degrees centigrade to provide the optimum temperature for the woodlice and therefore, the optimum temperature for the enzymes involved in their respiration.
2) The control tube is set up in exactly the same way as the woodlouse tube, except that the woodlice are substituted with glass beads of the same mass.
3) For 10mins, the tap is left open and the syringe is removed to allow the apparatus to equilibrate (accounting for any expansion that might cause the pressure to change inside) and the respiration rate of the woodlice to stabilise in their new environment.
4) When the 10mins is up, the tap is closed and the syringe is attached.
5) The syringe is used to reset the manometer, so that the ends of the fluid are at the same level on either side of the ‘U’ and the reading from the volume scale on the syringe (usually in cm3) is recorded.
6) As respiration occurs, the volume of the air in the test tube containing woodlice will decrease, due to the oxygen consumed during respiration (all of the CO2 produced is absorbed by the potassium hydroxide).
7) The decrease in the volume of air will reduce the pressure in the test tube, causing the colored fluid in the capillary tube of the manometer to move towards it.
8) After leaving the apparatus to run for a set period of time (e.g. 10mins), the syringe is used to reset the manometer and the reading on the syringe’s volume scale is recorded again. The difference between this figure and the figure taken at the start of the experiment is the oxygen consumption for this time period. You can use this to calculate a rate of respiration.
9) To check the precision of the results, the experiment is repeated and a mean volume of O2 is calculated.
- Oxygen consumption can also be calculated by recording the movement of the fluid in the manometer, read from the scale on the manometer itself.
What is a manometer?
A capillary tube filled with coloured fluid, with a calibrated scale.
When using a respirometer, how else other than by using readings from a gas syringe can the rate of oxygen consumption be calculated?
By recording the movement of the fluid in the manometer, read from the scale on the manometer itself.
