| Lesson Plan |
| Grade: |
Date: 25/02/2026 |
| Subject: Biology |
| Lesson Topic: state that glucose, fructose and maltose are reducing sugars and that sucrose is a non-reducing sugar |
Learning Objective/s:
- Describe the structural feature that makes a sugar a reducing sugar.
- Identify glucose, fructose and maltose as reducing sugars and sucrose as a non‑reducing sugar.
- Explain the chemical basis of Benedict’s/Fehling’s test results for these sugars.
- Compare open‑chain and cyclic forms regarding the presence of a free carbonyl group.
- Apply the concept to predict the reducing ability of other carbohydrates.
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Materials Needed:
- Projector or interactive whiteboard
- PowerPoint slides with sugar diagrams
- Benedict’s reagent, test tubes and water bath
- Sample solutions of glucose, fructose, maltose, sucrose
- Safety goggles and lab gloves
- Worksheet for recording test results
- Carbohydrate model kits (optional)
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Introduction:
Begin with a quick demonstration: a bright brick‑red precipitate forms when a reducing sugar reacts with Benedict’s reagent, catching students’ curiosity. Recall prior learning on carbohydrate classification and functional groups. Explain that by the end of the lesson they will be able to state which common sugars are reducing and why, and they will successfully interpret a Benedict’s test.
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Lesson Structure:
- Do‑now (5') – Students list examples of monosaccharides and predict their reducing ability.
- Mini‑lecture (10') – Present the concept of reducing sugars, free carbonyl groups, and the chemistry of Benedict’s test.
- Guided analysis (8') – Examine a table of glucose, fructose, maltose, and sucrose; discuss glycosidic bonds and reducing ability.
- Laboratory demonstration (12') – Perform Benedict’s test on the four sugars; students record colour changes.
- Think‑pair‑share (8') – Explain why sucrose gave a negative result using structural reasoning.
- Quick quiz (7') – Exit ticket: write a concise definition of a reducing sugar and name a non‑reducing sugar.
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Conclusion:
Summarise that the presence of a free aldehyde or ketone determines reducing ability, and that sucrose’s glycosidic bond blocks both anomeric carbons, making it non‑reducing. For the exit ticket, students write a concise definition and give an example. Assign homework to find another carbohydrate and predict whether it is reducing or non‑reducing.
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