Turn sucrose into detectable glucose
Compare glucose test-strip responses before and after treating a sucrose solution. This avoids assuming that sweetness is a laboratory measurement.
Use these original S&T teaching drafts after a teacher or technician has piloted the exact product, substrate and assay. Recipes and timing targets are proposed starting conditions, not validated performance claims. Review current SDS and institutional guidance; wear eye protection, avoid enzyme aerosols and splashes, and keep powders under technician control. No tasting. Keep controls at the same final volume, pH, temperature and stirring conditions. Plan reagent-specific waste disposal.
Invertase in nature
Yeasts and other organisms use invertase to access sucrose. Splitting this disaccharide releases glucose and fructose, which can enter metabolic pathways. The historical name refers to a change in optical rotation of the sugar mixture, not to physically turning a molecule upside down.
What chemical reaction does it catalyse?
Enzymes speed up a reaction without being consumed in the overall process. The preparation, accessible substrate and reaction conditions determine what you can measure.
Industrial applications
Invertase is used in confectionery and invert-sugar production, where sugar composition affects texture and crystallisation.
Experiment overview
Compare glucose test-strip responses before and after treating a sucrose solution. This avoids assuming that sweetness is a laboratory measurement.
Equipment and materials per working group
- 1% w/v sucrose in compatible buffer near pH 5
- Technician-prepared 1% w/v invertase stock in compatible diluent
- Three tubes, glucose-specific strips, glucose standard and pipettes
- 40°C water bath and timer
Plan a class of 30
Use 10 working groups of three. Multiply the per-group quantities in this guide by 10, then allow an appropriate preparation reserve. Keep concentrations unchanged when scaling. Assign a timer, a practical operator and a recorder, then rotate roles. Set up teacher-prepared comparison samples in advance where a reaction takes longer than the lesson.
Teacher and technician preparation
- Prepare powder stocks as a competent technician using the SDS and dust-control guidance; pupils receive liquid working solutions.
- Pilot 0.5 mL of 1% stock with 4.5 mL substrate: 5 mg enzyme product in 5 mL final mixture. Trial dilution if the result is immediate or saturates strips.
- Check enzyme-only and substrate-only backgrounds. Confirm glucose-strip performance at the sample pH and use the stated read time.
Use enough working enzyme to make a clear comparison in the intended time window. Do not automatically add more concentrate: reactions can finish before measurement, stocks can alter pH or background colour, and some substrates remain slow even at a high dose. Pilot the proposed recipe, then record the final preparation and dilution on the results sheet.
Step-by-step class method
- Label ENZYME, CONTROL and ENZYME BLANK.
- Add 4.5 mL sucrose to the first two and 4.5 mL buffer to the blank.
- Equilibrate at 40°C for 3 minutes.
- Add 0.5 mL selected invertase working solution to ENZYME and ENZYME BLANK; add 0.5 mL diluent to CONTROL.
- Test small fresh samples at zero, 5 and 10 minutes.
- Read strips at their specified development time and compare with the glucose standard.
- Dilute all relevant samples equally if above range.
- Explain why sucrose itself gives little signal on a glucose-specific test and why no tasting is needed.
What should students look for?
Treated sucrose should show glucose above both backgrounds if the method and preparation are compatible.
Interpretation and troubleshooting
Glucose strips report glucose, not total sugar. Do not interpret strip saturation as a quantitative conversion yield.
Questions for the class
- What changed in the enzyme-treated sample compared with the control?
- What bond or substrate does this enzyme act on?
- Which conditions did we keep the same, and why?
- Could colour, pH, warming, stirring or background sugars explain part of the result?
- What would you measure or change in a follow-up investigation?
Your investigation sheet
Name: ____________________ Group: ______ Date: __________
Prediction: _______________________________________________________
Enzyme preparation / batch: ________________________________________
Final working dilution and dose: ____________________________________
Substrate: _______________ pH: ______ Temperature: ______ °C
| Time / min | Enzyme + substrate | No-enzyme control | Enzyme-only blank / notes |
|---|---|---|---|
| 0 | ________________ | ________________ | ________________ |
| 2 | ________________ | ________________ | ________________ |
| 5 | ________________ | ________________ | ________________ |
| 10 | ________________ | ________________ | ________________ |
| Later: ___ | ________________ | ________________ | ________________ |
Conclusion supported by our control: _________________________________
One limitation and one improvement: __________________________________
Background sources and product details
This is an original teaching adaptation. External methods establish useful principles and assay formats; they do not validate the suggested doses for S&T preparations.