Respirometer Flashcards
What is the respiratory quotient and how is it calculated?
Its a measure of the ratio of the carbon dioxide produced by an organism to the oxygen consumed over a period of time.
Volume of CO2 produced
RQ = —————————————
Volume of 02 consumed
How does the respirometer work?
It has two identical closed vessels. One contains the living organism and the other acts as a thermobarometer.
What is a thermobarometer?
Small changes in temperature and pressure cause air in this vessel to expand or contract, compensating for similar changes in the first vessel.
Why do you weigh the organism?
It allows the rate of oxygen consumption to be calculated per gram per unit time.
How do you calculate oxygen uptake?
1) Add potassium hydroxide
2) The organisms take in oxygen within the system and the carbon dioxide produced is absorbed by the KOH
3) This causes a reduction in pressure and the dye moves towards the living organism.
How do you calculate carbon dioxide production?
1) Repeat the process for calculating oxygen uptake but replace the KOH with water.
2) Leave it in the same conditions and for the same length of time.
3) CO2 is not absorbed, if the dye doesn’t move, oxygen consumption = carbon dioxide consumption. Moves towards O2 consumption > CO2 production, and it if moves away CO2 production > O2 consumption.
What controlled variables need to be controlled?
Same apparatus, Same mass of living organism, same living organism, Temperature, Time period, If using plants cover with foil.
Why and how do you control those variables
1) Temperature - Water bath, affects the enzymes that control the metabolic processes within the organism so a higher temperature would increase the rate of respiration. Also can cause gases to expand / contract.
2) Covered with foil - To prevent photosynthesis occurring as it uses CO2.
3) Same organism - Ensures age and metabolic rate are controlled as far as possible. There will still be genetic variability.
What does an RQ value of 1 suggest?
Respiring carbohydrates
What does an RQ value of 0.9 suggest
Respiring proteins
What does an RQ value of 0.7 suggest
Respiring lipids
What does a RQ value >1 suggest
Respiring both aerobically and anaerobically.
