Practical investigation- Respirometer Flashcards
what is a respirometer
apparatus used to measure the rate of respiration of living organisms by measuring the rate of respiration by measuring rate of oxygen and co2
a respirometer usually has two tubes, what is in the two tubes
Tube 1- will have some organisms
Tube 2- will have an object of the same mass
the apparatus is left for 10 minutes, why
so equillibrium is reached
respiration rate is stabilised
what is the role of the syringe in the respirometer
the syringe can be depressed to restart the experiment when wanted, pushing it to balance the fluids in the manometer
what is important to record of the syringe when you begin the experiment
Its important to record at which mark the syringe is at the beginning.
why are the measurements;
oxygen g-1 h-1
Oxygen- volume of oxygen in what is being measured
g-1: this would be the mass of the organism being tested
h-1: measuring time
what solutions are used in the compensating chamber
sodium hydroxide or potassium hydroxide
an organisms will be placed on a platform in the compensating chamber to avoid it falling in the chemical. What is the name given to the platform
Guaze platform
what is the role of the sodium hydroxide or soda lime in the compensating chamber
absorbs carbon dioxide which is released in respiration.
Allows us to measure the o2 absorbed .
after time, the pressure in the chamber with the organisms in will exert less pressure, why is this
Because the organisms will absorb the oxygen in the tube, and the carbon dioxide is absorbed by the sodium hydroxide. Therefore less particles means less pressure
Why will the manometer fluid rise when the organism has been left to respire for a while
Because as they respire, o2 and co2 is being absorbed, therefore a reduction in pressure in the one chamber causes the liquid to rise in the manometer
what is the equation for respiration
02 + c6h12o6 = co2 + h20 + atp
when setting up the apparatus, the taps must be kept open. Why
Because it enables air in the apparatus to connect with the atmosphere
Due to the apparatus being in a water bath, it allows us to also use it to measure temperature. What is important to do before changing temperatures
It is important to leave apparatus and organisms to adjust to new temperatures.
when testing the effect of temp on respiration. What knowledge can you apply to a hypothesis
You can link knowledge of enzymes to the effect of temp. E.g. 40+ will denature enzymes
what type of equipment does the apparatus sit in
A temp controlled water bath
how do you reset the respirometer when measuring the effect of temperature
Allow air to re-enter the tubes via the screw cap and reset the manometer fluid using the syringe
Change the temperature of the water bath and allow the tubes to acclimate
then close the screw clip to begin the experiment
what part of the apparatus do you need to look at to measure the volume of oxygen absorbed
use the manometer reading to calculate the change in gas volume in a given time, y cm3 min-1
what must you do to the organisms before placing them in the apparatus
measure their mass
