C1.2.6 Variables affecting the Rate of Respiration

What 3 factors can be measured to determine the rate of respiration?

• oxygen uptake (→ in terms of changes in air pressure or volume)

• CO2 production

  • consumption of respiratory substrates such as glucose

what is a respirometer?

any device that measures the rate of cell respiration

What are the 3 main components of respirometers?

• Sealed glass/ plastic container (w/ enough air for organism to remain healthy)

• Base or alkali

• Capillary tube w/ fluid, connected to container

Why is it important to have an alkali in a respirometer?

It absorbs any CO2 released by the organism during respiration → ensures that any change in air volume is because of oxygen consumption

What is the function of the capillary tube in respirometers?

It measures changes in air volume inside the respirometer

How do you calculate the rate of respiration from experimental data?

goal: volume/ time , ex. mm³/min

• distance change of fluid in capillary tube should be converted into volume

• if using percentage changes, they are always compared to the control (0% change in IV)

Why is it important to control pressure, volume and temperature in cell respiration experiments? Give an example

because the three are interelated: ex, increased temperature increases pressure, making fluid in the capillary move when volume hasn’t changed

Name an alkali that is commonly used in respirometers

Potassium hydroxide

State some possible experiments using respirometers that don’t cause harm to the organism/s used

• Respiration rate of diff organisms

• Effect of temp on resp.

• Comparison of resp. rate in active vs inactive organisms