Q9 Respiration

Question 1

Prepare and show the production of alcohol by yeast — Procedure

Answer 1

1. Boil water to 100°C and allow to cool to remove oxygen from water.
   
   2. Add glucose to the cool boiled water.
   3. Add yeast and glucose to conical flask A.
   4. Add cooled, boiled glucose to flask B (control).
   5. Add oil to each flask to prevent air getting in.
   6. Attach a fermentation lock to each flask. Add limewater to them.
   7. Place both flasks in a water bath at 30°C overnight.

Question 2

Prepare and show the production of alcohol by yeast — To show the presence of alcohol

Answer 2

1. Filter the contents of each flask into test tubes.
   
   2. To each test tube add potassium iodide and sodium hypochlorite solutions (Iodoform test).
   3. Place in a water bath of 60°C for 5 minutes.
   4. Allow to cool.
   5. Record and compare results.

Question 3

Prepare and show the production of alcohol by yeast — Expected Result and Notes

Answer 3

• Expected Result: Clear – Pale Yellow Crystals form.
• Note: Temperature is an important factor because enzymes are sensitive to temperature change.
• You know fermentation is complete once CO₂ stops being produced.

Question 4

What does lime water test

Answer 4

Presence of CO2