12 / 04 Friday Learning objective:

1. 12 / 04 Friday Learning objective: Discuss how and why we use bacteria and fungi to make food such as yoghurt and beer.

2. Starter Describe the optimum condition for most bacteria and fungi Describe the difference between bacterial respiration and fungal respiration

3. Optimum conditions • Warmth (temperature ~ 37oC) • Nutrient • Moisture (Water) • Acidity (pH level) • Oxygen level (aerobic ones only)

4. Anaerobic respiration (Fermentation) • Homolactic fermentation – common in animals and bacteria • Glucose → Lactic acid + water + energy • Heterolatic fermentation – common in fungi • Glucose → Alcohol + CO2 + water + energy

5. Assessment Overview • Week 12 Mon & Tue → Making yoghurt • Week 12 Thu & Fri → Research Project • Week 1 Mon → Revision Work • Week 1 Tue & Thu → Report

6. Assessment Overview Use observations, findings & biological ideas to describe and explain: howand why humans use bacteria and fungi how humans are affected by bacteria and fungi Also describe how this knowledge impacts your personal actions or everyday life

7. Achieved – Describebiological ideas and how humans use / or are affected by two micro-organisms. • Merit – Explainbiological ideas and how humans use / or are affected by two micro-organisms. • Excellence – Explain with significant linksbetween biological ideas and how humans use / or are affected by two micro-organisms.

8. Example – Achieved The results from our experiment showed that the yoghurt mixture incubated at 40 oCwas the thickest. It becamethick because of the lactic acid made by the bacteria.

9. Example – Merit The results from our experiment showed that the yoghurt mixture incubated at 40 oC was the thickest. The yoghurt mixture incubated at 60 oCdid not thicken at all and the yoghurt mixture incubated at 30 oC thickened very little.

10. Example – Merit (contd.) This would bebecause 40 oC is the optimum temperature for bacteria to reproduce by binary fission. Having a greater number ofbacteria presentmeans they produce lots of lactic acid by homolactic fermentation (anaerobic respiration in bacteria).

11. Example – Merit (contd..) At60 oC, the temperature would be too high for bacteria to survive, so there was no bacteria to produce lactic acid which is why the yoghurt was not thickened at all. At 30 oC, although bacteria can survive and reproduce, their reproduction and respiration rate would be slower so smaller amount of lactic acid was produced which is why the yoghurt was less thick.

12. Example – Excellence (Merit +) Bacteria in the mixture feed on lactose in the milk by performing extra-cellular digestion and they change the lactose into lactic acid through homolactic fermentation (anaerobic respiration in bacteria). The lactic acid makes the sour taste in the yoghurt and also makes it thicken by coagulating milk protein.

13. Example – Excellence (Beer) Usually using a greater amount of sugar in the process would make more alcoholic beer as the yeasts will keep producing alcohol by heterolactic fermentation (anaerobic respiration in fungi) process until the point is reached where the yeasts are unable to tolerate the level of alcohol. If the yeasts have low tolerance for alcohol, they will die earlier and the remaining sugar makes the beer sweeter.

14. Revision List • Extracellular digestion • Reproduction (binary fission, spores) • Anaerobic respiration / Fermentation (homolactic, heterolactic) • Optimum conditions • Process of making yoghurt & beer

15. Ginger Beer – Making Links (examples) • heterolactic fermentation • CO2 -> carbonic acid -> pH -> bacteria control • Glucose level -> Alcohol level & Sweet taste • Temperature control • Pressure control

16. Alcohol & CO2 = ???