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.
   
   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.