Light Energy
Sunlight is captured by chlorophyll pigments inside chloroplasts, primarily in plant leaves.
What is Photosynthesis?
The biochemical process by which organisms use light energy to synthesize organic compounds from carbon dioxide and water.
Water
Absorbed through roots, water is split during the light-dependent reactions, releasing oxygen as a byproduct.
Carbon Dioxide
CO₂ enters leaves through stomata and is fixed into glucose during the Calvin cycle.
Glucose
The sugar produced stores energy and serves as building blocks for cellulose, starch, and other biomolecules.
/ EQUATION
The Chemical Equation
Photosynthesis can be summarized in one elegant reaction.
6CO2
+
6H2O
+
light
C6H12O6
+
6O2
Six molecules of carbon dioxide and water, powered by sunlight, produce one glucose molecule and six oxygen molecules.
~50%
of Earth's oxygen comes from ocean phytoplankton
100B+
tons of CO₂ fixed by photosynthesis each year
3.5B
years photosynthesis has shaped our atmosphere
/ PROCESS
Two Stages
Photosynthesis occurs in two interconnected stages inside the chloroplast.
01
Light-Dependent Reactions
Thylakoid membranes- Chlorophyll absorbs photons of light
- Water molecules are split (photolysis)
- ATP and NADPH are produced
- Oxygen is released into the atmosphere
Light → ATP + NADPH → O₂
02
Calvin Cycle
Stroma- CO₂ is fixed by the enzyme RuBisCO
- ATP and NADPH from Stage 1 power the cycle
- 3-carbon molecules (G3P) are formed
- G3P is assembled into glucose
CO₂ → G3P → Glucose
Inside the Chloroplast
/ FACTORS
Environmental Factors
The rate of photosynthesis depends on environmental conditions. Adjust the sliders to see how each factor influences the process.
Photosynthesis Rate
72%
Optimal conditions — photosynthesis is running efficiently.
Light
Too little light limits energy capture. Beyond a saturation point, more light doesn't increase the rate.
CO₂
Carbon dioxide is often the limiting factor in enclosed environments. Higher CO₂ can boost growth up to a plateau.
Temperature
Enzymes like RuBisCO work best around 25–35°C. Extreme heat denatures proteins and slows the Calvin cycle.
Water
Water stress closes stomata, reducing CO₂ intake. Dehydration also disrupts the light reactions.
/ QUIZ
Test Your Knowledge
Where do the light-dependent reactions of photosynthesis take place?
What gas is released as a byproduct of photosynthesis?
Which molecule stores the energy produced in the light reactions for use in the Calvin cycle?
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