A leaf makes food

The idea

In photosynthesis autotrophs convert carbon dioxide and water into carbohydrates, a stored form of energy, in the presence of sunlight and chlorophyll, which is found in cell organelles called chloroplasts.

A food factory with no kitchen

A plant has no mouth and no stomach. Yet its green leaves make food. Think about what a leaf might need to do that.

What do you think a leaf needs to make food?

• Sunlight only
• Sunlight and water
• Sunlight, water, carbon dioxide and a green substance in the leaf

Take one thing away

The leaf is making food. Switch off one thing at a time and watch the pieces of food. Can the leaf do without any of the four?

Four things, one food

In photosynthesis, autotrophs convert carbon dioxide and water into carbohydrates, a stored form of energy, in the presence of sunlight and chlorophyll. Chlorophyll is found in cell organelles called chloroplasts.

The food that is made is carbohydrate. It is a stored form of energy for the plant.

• Needed | Where it comes from
• Carbon dioxide | From the air, through tiny pores (stomata) in the leaves
• Water | From the soil, taken up by the roots
• Sunlight | From the Sun
• Chlorophyll | In the chloroplasts: the green dots in leaf cells

Notes

In photosynthesis autotrophs convert carbon dioxide and water into carbohydrates, a stored form of energy, in the presence of sunlight and chlorophyll, which is found in cell organelles called chloroplasts.

Check yourself

Which two are converted into carbohydrates in photosynthesis?

Where is chlorophyll found?

A plant is kept in a dark cupboard. It has water and carbon dioxide. Can it do photosynthesis?

Which sentence is correct?

• Sunlight and chlorophyll. Both are needed, but they are not what is converted. Sunlight gives the energy, and chlorophyll is in the chloroplasts.
• Carbon dioxide and water — correct. Yes! Autotrophs convert carbon dioxide and water into carbohydrates.
• Carbohydrates and chlorophyll. Carbohydrates are what the leaf makes, not what it starts with.
• In the roots, with the water. Roots take up water from the soil. Chlorophyll is in the chloroplasts of cells.
• In the sunlight. Sunlight is energy that comes from the Sun. Chlorophyll is a substance inside chloroplasts.
• In chloroplasts, the green dots in leaf cells — correct. Yes! Chloroplasts are cell organelles that contain chlorophyll.
• No, sunlight is missing — correct. Yes! Photosynthesis needs sunlight, as well as carbon dioxide, water and chlorophyll.
• Yes, water and carbon dioxide are enough. The two raw materials are there, but sunlight is also needed.
• Yes, chlorophyll alone is enough. Chlorophyll is only one of the four things needed. The sunlight is missing.
• Sunlight alone is enough to make food. Sunlight is needed, but so are carbon dioxide, water and chlorophyll.
• A leaf needs sunlight, carbon dioxide, water and chlorophyll together — correct. Yes! Take any one away and the leaf stops making food.
• The plant takes in ready-made carbohydrates from the soil. It makes carbohydrates itself, from carbon dioxide and water.