Photosynthesis

Explain the photosynthesis equation and the factors that limit it.

~19 min Biology

0 of 2 completed

Photosynthesis converts light energy into chemical energy stored in glucose.

In this lesson you will:

Write the photosynthesis equation.
Identify the role of chlorophyll and stomata.
Explain limiting factors.

The Equation

Carbon dioxide + water → glucose + oxygen, using light energy absorbed by chlorophyll: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂.

Where It Happens

Photosynthesis occurs in chloroplasts, mainly in leaf cells. Chlorophyll absorbs red and blue light and reflects green. Stomata allow carbon dioxide in and oxygen out.

Limiting Factors

The rate increases with light intensity, carbon dioxide concentration and temperature, until another factor becomes limiting.

Test for starch

Boil a leaf in water to kill it, then in ethanol to remove chlorophyll.

Add iodine solution. A blue-black colour shows starch was made.

Tip Photosynthesis and respiration are not opposites in timing: plants respire all the time, but photosynthesise only in light.

Practice

Write the word equation for photosynthesis.
Name the gas released and the gas used.
Explain how a shortage of carbon dioxide limits the rate.

Recap

Photosynthesis uses light, carbon dioxide and water to make glucose and oxygen. Several factors can limit the rate.

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Course contents

Nutrition and Transport in Plants

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