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examBoard: Pearson Edexcel
examType: IGCSE
lessonTitle: Photosynthesis Equations
Photosynthesis is one of the most important processes on Earth! It's how plants make their own food using sunlight. Understanding the equations behind photosynthesis helps us see exactly what goes in and what comes out during this amazing process.
Key Definitions:
Photosynthesis is vital because it:
Photosynthesis takes place in the chloroplasts of plant cells, particularly in the leaves. Leaves are adapted with:
Before we look at the chemical symbols, let's understand the process in words:
Carbon dioxide + Water → Glucose + Oxygen
(with light energy and chlorophyll)
This means that plants take in carbon dioxide from the air and water from the soil. Using energy from sunlight (captured by chlorophyll), they convert these raw materials into glucose (a sugar) and release oxygen as a waste product.
The chemical equation shows the exact molecules involved:
6CO2 + 6H2O → C6H12O6 + 6O2
(with light energy and chlorophyll)
Let's break down what each part means:
Notice how the equation is balanced? This means the number of atoms of each element is the same on both sides:
This balance is important because it follows the law of conservation of mass - matter cannot be created or destroyed in a chemical reaction, only rearranged.
Light energy is crucial for photosynthesis. Without it, the reaction cannot happen. This is why plants need sunlight to grow!
Chlorophyll captures light energy from the sun, particularly red and blue wavelengths.
The light energy is converted to chemical energy stored in the bonds of glucose.
Plants store excess glucose as starch or convert it to other compounds like cellulose.
Several factors can speed up or slow down how quickly photosynthesis happens:
A limiting factor is anything that restricts the rate of photosynthesis when in short supply. The main limiting factors are:
More light generally means faster photosynthesis, up to a point. After that, another factor becomes limiting.
Enzymes work best at their optimum temperature (around 25-30°C for most plants). Too hot or too cold slows the reaction.
Higher CO2 levels can increase photosynthesis rate, which is why some greenhouses add extra CO2.
Commercial greenhouses manipulate all three limiting factors to maximise plant growth:
This allows farmers to grow crops year-round and increase yields significantly compared to outdoor farming.
Scientists often use graphs to show how different factors affect photosynthesis rates. Here's how to understand them:
As light intensity increases:
As temperature increases:
Understanding photosynthesis equations has many real-world applications:
Scientists are working on artificial photosynthesis technology that could help reduce carbon dioxide levels in the atmosphere while producing clean fuels. These systems try to mimic the chemical reactions of natural photosynthesis but with different catalysts and materials.
To recap what we've learned:
Remember that photosynthesis is the foundation of almost all life on Earth. The oxygen we breathe and the food we eat ultimately depend on this remarkable process!
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