1.1. Fig. 5 shows the respirometer apparatus used by a teacher for measuring the rate of oxygen consumption of seeds during aerobic respiration.

Fig. 5

Explain the role of potassium hydroxide (KOH) in the apparatus.

1.2. The teacher set up boiling tube 1, ensuring that the volume of water and KOH was equal to the volume of seeds in boiling tube 2.

Suggest why it was important that these volumes were the same.

1.3. Tube 1 in Fig. 5 functions as an experimental control.

Suggest a suitable alternative control tube for this investigation.

1.4. The teacher observed that the coloured liquid in the capillary tube moved 2 cm in 24 hours.

The internal diameter of the capillary tube was 1 mm and the mass of the seeds used was 1.8 g.

Calculate the rate of oxygen consumption per gram of seeds in cm³ g^-1 hour^-1 using the formula below. Give your answer in standard form.

volume = πr²l

1.5. Cyanide is a chemical that inhibits cytochrome c oxidase, a protein in the electron transport chain.

State and explain the effect that the addition of cyanide would have on the movement of the coloured liquid in the respirometer.