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Science

Food chains

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Plants and photosynthesis

Before we look at food chains we will go over the way green plants capture energy from the Sun to make food. This is the start of all the food chains we will look at.

Plants and photosynthesis

Animals eat food to get their energy. But green plants don't. Instead they make their own food, glucose, in a process called photosynthesis. We say that plants can photosynthesise.

These are the things that plants need for photosynthesis:

  • carbon dioxide

  • water

  • light

These are the things that plants make by photosynthesis:

  • glucose

  • oxygen

We can show photosynthesis in a word equation, where light energy is shown in brackets because it is not a substance:

carbon dioxide + water (+ light energy)glucose + oxygen

Plants get carbon dioxide from the air through their leaves, and water from the ground through their roots. Light energy comes from the sun.

The oxygen produced is released into the air from the leaves. The glucose produced can be turned into other substances, such as starch, which is used as a store of energy. This energy can be released by respiration.

Where does photosynthesis take place?

Photosynthesis takes place inside plant cells in small things called chloroplasts. Chloroplasts contain a green substance called chlorophyll. This absorbs the light energy needed to make photosynthesis happen. Plants can only photosynthesise in the light.

The plant cell is surrounded by a cell wall for structure. Inside this is the cell membrane and this contains the cytoplasm. There are chloroplasts and one nucleus in the cytoplasm, and in the centre of the cell is a large vacuole.

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