Photosynthesis Explorer

Photosynthesis Explorer is a five-level 3D simulation for secondary biology. Students start with a leaf cut open, tap any tissue to learn its job, then zoom into a chloroplast, onto a thylakoid membrane where electrons flow from water through photosystem II and photosystem I while protons drive ATP synthase, and into the Calvin cycle where carbon atoms can be counted. The rate comes from the leaf model plant scientists use, so changing light intensity, light colour, CO₂ and temperature gives realistic numbers, a limiting factor and a light compensation point. Switches add drought, the herbicide DCMU and cyclic electron flow, and a 3D rate surface with recorded readings supports fair-test investigations.

• Start on the Leaf level, tap the palisade cells, the spongy cells and a stoma, then tap a chloroplast to zoom inside it.
• On the Thylakoid membrane level, follow one yellow electron from water to NADPH and watch the ATP synthase rotor speed up as you raise the light.
• Turn on Add DCMU herbicide and explain why oxygen release stops while photosystem II glows red.
• Count carbons on the Calvin cycle level: check that every 3 CO₂ fixed gives 1 G3P that leaves the cycle.
• Raise the temperature to 38 °C and compare the RuBisCO grabs O₂ readout with the value at 25 °C.
• On the Rate graph, drag the ball to find where light stops being the limiting factor, then record readings at three CO₂ levels.

1. 1Describe where the light-dependent reactions and the Calvin cycle happen inside a chloroplast.
2. 2Explain how electron flow through photosystems II and I produces ATP, NADPH and oxygen from water.
3. 3Identify the limiting factor for photosynthesis from changes in light intensity, CO₂ concentration and temperature.
4. 4Explain how stomatal closure, herbicides and photorespiration reduce the rate of photosynthesis.
5. 5Plan a fair test by changing one variable at a time and recording the rate.

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