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Microbes · Chapter 7: Investigating yeast (AS 92020)

Year 11 SCX · About 17 minutes with activities · Turn your sound on

Chapter 7 · Investigating yeast
Arohasame results
Samsame results
Described the dataAroha · Achieved
Explained + analysedSam · Excellence
Practice onlyyour teacher runs the real one
Merittemperature → respiration
Excellencerespiration → environment
Glucosefood in
Carbon dioxidewaste out
Ethanolwaste out
Out by diffusionhigh → low concentration
Count the bubblesCO₂ per minute
Enzymea protein
Active sitesubstrate binds here
Substrateglucose
Risingmore collisions
Peakthe optimum
Fallingenzymes denature
Yeast + sugar solutionin a test tube
Change: temperatureindependent variable
Measure: bubblesdependent variable
Keep the sameyeast, sugar, time
Ethanol builds uptoxic waste
Glucose used upfood runs out

Chapter 7 recap

  • AS 92020 ladder: Achieved describes a life process and a factor using observations; Merit links a change in the factor to the life process; Excellence analyses how the life process changes the environment.
  • Fermentation: glucose → ethanol (alcohol) + carbon dioxide + ATP. Count CO₂ bubbles per minute to measure the rate of respiration. Fair test: change temperature only, repeat and average.
  • Temperature: more kinetic energy → more collisions → faster respiration, up to the optimum; above it enzymes denature. Environment: respiration uses up glucose and builds up toxic ethanol, slowing itself down.
  • Next: Chapter 8 · Pathogens and food safety

Same experiment, same results: why did one write-up get Excellence?

Chapter 7 · About 17 minutes · sound on

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