Photosynthesis Simulator: Inside the Chloroplast
Zoom inside a chloroplast and control light, CO₂, temperature and water to see the light-dependent and light-independent reactions speed up, slow down or stall.
Rate vs light intensity at your current CO₂/temp/water. Red dot = your setting.
Rate vs temperature at your current light/CO₂/water. Red dot = your setting.
About the Photosynthesis Simulator: Inside the Chloroplast
Free photosynthesis simulator: inside the chloroplast. Zoom inside a chloroplast and control light, CO₂, temperature and water to see the light-dependent and light-independent reactions speed up, slow down or stall. Drag, change the sliders and see the result live. No sign-up, works on phone and computer. Built for botany, the photosynthesis simulator: inside the chloroplast runs instantly in your browser: change a setting or drag an object and the result updates at once, so you learn by trying things out rather than only reading about them.
Zoom inside a chloroplast and control light, CO₂, temperature and water to see the light-dependent and light-independent reactions speed up, slow down or stall. Use it to explore botany ideas at your own pace, then check what you found against the key ideas further down this page.
How to use the Photosynthesis Simulator: Inside the Chloroplast
- Use the controls to change Light intensity, CO₂ concentration, Leaf temperature, Water availability. The simulation reacts instantly.
- Press "Full sun", "Deep shade", "Drought (stomata closed)", "Reset to defaults" to start, reset or change what is happening.
- Where you see a glowing handle, object, weight or atom, drag it with your mouse or finger. Everything responds in real time.
- Watch the readouts and graphs update as you experiment, and compare what you see with the key ideas below.
Things to try
- Try Full sun, then Deep shade, and read the limiting stage readout each time.
- Use the drought preset and watch the stomata close in the zoomed view.
- Drag temperature past the optimum and watch the rate curve fall sharply.
- Find the light level where the rate curve visibly flattens (saturation).
Key ideas you can learn
- The rate of photosynthesis rises with light intensity then saturates once the light-dependent reactions run as fast as they can.
- Enzymes in the Calvin cycle have an optimum temperature; going too far past it sharply cuts the rate.
- Low water makes stomata close, starving the Calvin cycle of CO₂ even if light is plentiful.
- Oxygen and glucose are produced in a fixed 6:1 ratio from water and carbon dioxide.
Where this is used in the real world
Greenhouse growers pump in extra CO₂ and control temperature for exactly this reason: to keep every factor from becoming the bottleneck and maximise crop photosynthesis.
Who is this simulation for?
Students, teachers and curious learners of all ages.
For teachers: project it on the board, let students predict what will happen, then run it together. For students: change one thing at a time and write down what changes.
Frequently asked questions
Why does raising light intensity eventually stop increasing the rate?
Past a point the light-dependent reactions are running as fast as the leaf's machinery allows, so CO₂ fixation in the Calvin cycle becomes the new bottleneck.
Why does drought reduce photosynthesis even in bright light?
Drought closes the stomata to save water, which also blocks CO₂ from entering the leaf, starving the Calvin cycle.
Is the Photosynthesis Simulator: Inside the Chloroplast free to use?
Yes. It is completely free, with no signup, no download and no ads inside the simulation. It runs in your web browser.
Does the Photosynthesis Simulator: Inside the Chloroplast work on a phone or tablet?
Yes. It uses touch as well as the mouse, so you can drag objects with your finger. A larger screen makes the controls easier to see.