IB Biology IA idea · Enzymes, food and metabolism
IB Biology IA idea: yeast fermentation with different sugars and amounts
Yeast turns sugars into carbon dioxide, but not equally fast. Compare sugars and find where too much starts to hurt.
These ideas are starting points, not an IA to copy. Never copy an idea blindly: make the question, method and analysis your own, and check your plan with your teacher.
Example research question
How does glucose concentration (0, 5, 10, 15, 20 and 25 %) affect the rate of carbon dioxide production (cm³ min⁻¹) by baker's yeast at 35 °C in the first 10 minutes, measured by gas collection over water?
Change the system, the range or the method so the question is yours. Check it against the research question checklist in our Biology IA guide.
Variables
- You change
- glucose concentration, 0 to 25 percent, 6 or more values (or sugar type with equal moles)
- You measure
- carbon dioxide produced in the first 10 minutes, cm3, as a rate
- You keep the same
- same yeast mass and batch
- same temperature in a water bath
- same total volume
- same time for settling
Method
Mix baker's yeast with sugar solutions in a sealed syringe or bottle and collect gas over water or measure pressure with a sensor. Repeat the series three times.
Data analysis
Rate against concentration, mean and standard deviation; compare the curve with Michaelis-Menten behaviour and with the drop caused by osmotic stress at high concentration. ANOVA.
How it works
You change Glucose concentration (%) and measure CO₂ production rate (cm³ min⁻¹) in Baker's yeast suspension, keeping Yeast mass, Temperature, Solution volume the same. Expect a graph of Rate of CO₂ production / cm³ min⁻¹ against Glucose concentration / %: The rate climbs, then levels off as enzymes saturate.
Make it yours
Test disaccharides such as sucrose and maltose against lactose, which yeast cannot digest.
Safety
Warm water only. Keep sealed vessels vented to avoid pressure build-up.
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