Lesson Plan

• Describe the specific role of PSI in cyclic photophosphorylation.
• Explain the step‑by‑step mechanism from photoactivation of P700 to ATP synthesis.
• Compare cyclic and non‑cyclic photophosphorylation in terms of electron flow and products.
• Analyse how the pathway balances the ATP/NADPH ratio required by the Calvin‑Benson cycle.

• Projector and screen
• PowerPoint slides or digital diagram of cyclic photophosphorylation
• Printed worksheet with a labeled thylakoid membrane
• Whiteboard and markers
• Student clickers or online quiz platform for quick checks

Begin with a striking image of a chloroplast and ask students how plants meet fluctuating energy demands. Recall the basic light‑dependent reactions and the need for ATP beyond what non‑cyclic photophosphorylation provides. State that by the end of the lesson they will be able to trace the cyclic pathway and justify its biological importance.

1. Do‑now (5'): Quick quiz on the two photosystems and their products.
2. Mini‑lecture (10'): Present the cyclic pathway using the slide diagram, highlighting PSI‑only involvement.
3. Guided walkthrough (12'): Step‑by‑step explanation of the six mechanistic stages, pausing for student questions.
4. Interactive activity (10'): Students label a blank thylakoid diagram on the worksheet in pairs.
5. Comparison task (8'): Small‑group discussion contrasting cyclic vs. non‑cyclic photophosphorylation, reporting key differences.
6. Check for understanding (5'): Clicker poll with scenario questions about ATP demand.

Summarise that cyclic photophosphorylation uses only PSI to generate ATP, reinforcing its role in balancing energy needs during the Calvin cycle. Have students complete an exit ticket stating one situation where the plant would rely on this pathway. Assign a short homework: write a paragraph linking ATP production in cyclic photophosphorylation to real‑world plant stress responses.