respiration experiments 2 Flashcards
how can the rate of oxygen consumption be measured
by using a respirometer
what can respirometers be used to indicate
Respirometers can be used to indicate the rate of aerobic respiration by measuring the amount of oxygen
consumed by an organism over a period of time.
what is step 1 to the respirometer experiment
The apparatus is set up as shown on the right, partially
submerged in a water bath at 15 °C to provide the optimum
temperature for the woodlice and therefore, the optimum
temperature for the enzymes involved in their respiration.
what is step 2 to the respirometer experiment
The control tube is set up in exactly the same way as the
woodlouse tube, except that the wood lice are substituted
with glass beads of the same mass
what is step 3 to the respirometer experiment
For ten minutes, 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
what is step 4 to the respirometer experiment
When the ten minutes is up, the tap is
closed and the syringe is attached.
what is step 5 to the respirometer experiment
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.
what is step 6 to the respirometer experiment
As respiration occurs, the volume of the air in the test tube containing woodlice will decrease, due to the
oxygen consumed during respiration (all the CO2 produced is absorbed by the potassium hydroxide).
what is step 7 to the respirometer experiment
The decrease in the volume of the air will reduce the pressure in the test tube, causing the coloured fluid
in the capillary tube of the manometer to move towards it.
what is step 8 to the respirometer experiment
After leaving the apparatus to run for a set period of time (e.g. 10 minutes),
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.
what is step 9 to the respirometer experiment
To check the precision of the results, the experiment is repeated
and a mean volume of O , is calculated.
how else can oxygen consumption also be calculated
Oxygen consumption can also be calculated by recording the movement
of the fluid in the manometer, itself
