Plants perform photosynthesis by using sunlight, water, and carbon dioxide to create their own food (sugars) and oxygen.
Here's a more detailed breakdown of the process:
The Photosynthesis Process Explained
Photosynthesis is a complex process, but it can be broken down into two main stages: the light-dependent reactions and the light-independent reactions (also known as the Calvin cycle).
1. Light-Dependent Reactions (The "Photo" Part)
- Absorption of Light: Chlorophyll, a green pigment found in chloroplasts (organelles within plant cells), absorbs sunlight.
- Water Uptake: Plants take in water (H2O) through their roots. This water is transported to the leaves.
- Electron Transport: The light energy absorbed by chlorophyll energizes electrons from water molecules. This process splits water into oxygen, protons (H+), and electrons. The oxygen is released into the atmosphere.
- Energy Production: The energized electrons move through an electron transport chain, releasing energy. This energy is used to create ATP (adenosine triphosphate) and NADPH, which are energy-carrying molecules.
2. Light-Independent Reactions (The "Synthesis" Part or Calvin Cycle)
- Carbon Dioxide Uptake: Plants take in carbon dioxide (CO2) from the air through small pores called stomata on their leaves.
- Carbon Fixation: Inside the chloroplast, the enzyme RuBisCO combines CO2 with a five-carbon molecule called RuBP (ribulose-1,5-bisphosphate). This forms an unstable six-carbon compound that quickly breaks down into two molecules of a three-carbon compound.
- Sugar Creation: ATP and NADPH (created during the light-dependent reactions) provide the energy to convert these three-carbon molecules into glucose (sugar), which the plant uses as food.
- RuBP Regeneration: Some of the three-carbon molecules are also used to regenerate RuBP, so the cycle can continue.
Summary in Simple Terms
Think of it this way:
- Plants grab sunlight, water, and carbon dioxide.
- Using sunlight's energy, they split water, releasing oxygen.
- They use the energy to turn carbon dioxide and the remaining parts of water into sugar.
Equation for Photosynthesis
The overall chemical equation for photosynthesis is:
6CO2 + 6H2O + Light Energy → C6H12O6 + 6O2
This means:
- Six molecules of carbon dioxide plus six molecules of water, in the presence of light energy, produce one molecule of glucose (sugar) and six molecules of oxygen.
