Respiration Experiments Flashcards
What are the two ways respiration can be measured?
1) gas syringe
2) respirometer
What is yeast and how does it respire?
Yeast are single celled organisms that can be grown in culture. They can respire aerobically when plenty of oxygen is available and anaerobically when oxygen isn’t available. Both aerobic and anaerobic respiration produce carbon dioxide so the rate of carbon dioxide production can be used as a measure of the rate of respiration.
How can we measure the rate of respiration using a gas syringe?
Measure carbon dioxide production by o=collecting it with a gas syringe
How do we measure the rate of aerobic respiration in yeast?
1) place a known volume and concentration of a respiratory substrate such as glucose into a test tube.
2) add a known volume of a pH buffer solution to keep the pH constant during the practical (for optimum enzyme pH)
3) place the test tube in a water bath for 10 minutes to allow the solutions to equilibrate to the correct temperature.
4) add a known mass of dried yeast to the test tube and stir for 2 mins
5) attach a bung and gas syringe in the top of the test tube and ensure the syringe is set at zero
6) start a stopwatch and measure the volume of Cabo dioxide produced per minute for 10 mins
7) a control experiment should be set up with no yeast present. No carbon dioxide should be produced when yeast is not present
The experiment should be repeated 3 times at each temperature and a mean calculated
How do we measure the rate of anaerobic respiration in yeast?
1) set up the apparatus as described in aerobic respiration experiment
2) however, after the yeast has dissolved some liquid paraffin is trickled down inside the test tube and settles on top to cover the surface to prevent oxygen from entering so the conditions are anaerobic
3) follow same procedure as aerobic for collecting carbon dioxide
What is a respirometer?
A respirometer can be used to measure the rate of aerobic respiration by measuring the volume of oxygen consumed over a period of time
How is the apparatus of respirometer set up?
The apparatus is set up, as shown in the diagram, and placed in a water bath to maintain a constant optimum temperature for enzyme activity in the organisms such as woodlice, maggots, or germinating seeds
State 3 reasons why the apparatus of respirometer is left for 10 minutes
1) allow equilibrium to be reached
2) allow for pressure changes in the apparatus
3) allow the rate of respiration to stabilise
Regarding respirometers, what causes the coloured liquid to move towards the respiring organism?
1) as the organism aerobically respires, oxygen is consumed
2) carbon dioxide will be released, which is then absorbed by the potassium hydroxide
3) results in decrease in pressure causing coloured liquid to move towards the organism.
How can we work out the volume of oxygen consumed?
This calculated volume can be used to work out rate of aerobic respiration by dividing the volume by the time
What do more complex respirometers look like?
They are attached to a control tube that has been set up in exactly the same way but have glass beads of the same volume instead of the living organism
How do you use a respirometer to determine volume of carbon dioxide produced?
If the spirometer is set up with water instead of potassium hydroxide and the experiment is repeated, then if the coloured liquid doesn’t move the volume of oxygen consumed must equal the volume of carbon dioxide produced, which would mean that glucose must be the respiratory substrate that the organism is using (RQ=1)
If however another respiratory substrate is respired then there will be less carbon dioxide produced than oxygen consumed.
Volume of carbon dioxide can be determined using the difference in volumes with potassium hydroxide and without potassium hydroxide.
How do you use a respirometer to investigate anaerobic respiration?
If a simple respirometer is set up with years and something that absorbed oxygen then the conditions would be anaerobic. In anaerobic respiration with yeast, carbon dioxide would be given off and the increase in pressure would cause the coloured fluid to move away from the yeast in the capillary tubing.
