🌿 Photosynthesis — Leaf Cross-Section Lab

Zoom into a leaf: light hits chloroplasts, CO₂ slips in through stomata, water arrives from the roots — and sugars plus the oxygen you're breathing come out. Drive it with light and CO₂ and find the limiting factor.

6 CO₂ + 6 H₂O + light → C₆H₁₂O₆ + 6 O₂
📖 Key facts

Photosynthesis runs in two stages inside chloroplasts. In the light reactions (thylakoid membranes) chlorophyll absorbs red and blue light — reflecting green, which is why leaves look green — and uses that energy to split water, releasing O₂ and charging ATP/NADPH. In the Calvin cycle (stroma) that energy fixes CO₂ into sugar. Light-dependent and light-independent — exactly what the sliders show: starve either input and the whole pipeline slows.

Leaves balance photosynthesis against water loss: stomata open to let CO₂ in also let water vapour escape (transpiration), so plants close them in drought — cutting CO₂ supply. Photosynthesis stores ~120 billion tonnes of carbon a year and produced the oxygen in Earth's atmosphere over ~2 billion years (the Great Oxidation Event).