Using a respirometer to carry out investigations into respiration rate and RQ values

Aimed at advanced biology students, this resource leads students through the design and use of a respirometer. The first few questions deal with causes of pressure changes inside a respirometer tube and predicting the direction in which fluid within a manometer tube would flow. The worksheet then moves on to cover two different investigations - measuring the amount of oxygen consumed over time and measuring the amount of carbon dioxide produced over time. Tables for the recording of data and calculations (e.g. converting distance measurments to volumes) are provided along with questions that check understanding. The data gathered from both oxygen consumption and carbon dioxide can be plotted as graphs to calculate rate of respiration or used to calculate RQ values, indicating which respiratory substrate is being used by the organisms under test (blowfly larvae are suggested). The second worksheet in this resource deals specifically with a thermo-barometrically balanced respirometer and calculation/interpretation of RQ values.

Key words: respirometer, manometer, blowfly larvae, maggots, rate, RQ value, volume, distance, temperature, control, potassium hydroxide, thermo-barometrically balanced