Animal and plant cells: chloroplasts

The idea

Chloroplasts are the organelles in plant cells where photosynthesis occurs. They contain the green pigment chlorophyll, which absorbs light energy so that the plant can make glucose from carbon dioxide and water. Chloroplasts are found in the green parts of plants, such as the leaves, and are numerous in cells like palisade cells. They are absent from animal cells and from plant cells that do not photosynthesise, such as root hair cells. When plant cells are viewed under a light microscope, chloroplasts appear as small green, oval structures in the cytoplasm. Their presence is a key feature that distinguishes plant cells from animal cells.

For example: A palisade cell contains many chloroplasts near the top of the leaf, which increases the amount of light absorbed for photosynthesis.

What earns the marks

• Chloroplasts are the site of photosynthesis in plant cells.
• In a light microscope image, chloroplasts appear as green, oval structures.

Common mistakes and how to put them right

• Thinking chloroplasts are present in all plant cells.

  Put it right: They are absent in non-photosynthetic plant cells such as root hair cells.

• Confusing chloroplasts with chlorophyll.

  Put it right: Chloroplasts are the organelles; chlorophyll is the green pigment inside them.

• Stating that chloroplasts release energy from glucose.

  Put it right: Chloroplasts absorb light energy to make glucose; mitochondria release energy from glucose.

Exam tips

• When labelling a plant cell diagram, write 'chloroplast' clearly and include the green colour if asked to describe.
• If asked to compare plant and animal cells, state that chloroplasts are present in plant cells but absent in animal cells.
• Link chloroplast function to photosynthesis and the presence of chlorophyll to gain full credit in explanation questions.