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What are cells?
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Cells are the basic building blocks of life, and almost all living things are made up of them. The human body contains billions of tiny cells. Cells have three main parts. In the middle is the nucleus, which is the cell's control centre. This is surrounded by a fluid called cytoplasm, where energy is made. Around the outside is the cell membrane, which allows certain substances to enter and leave the cell. | | Body cells are designed to perform specific tasks. They reproduce by dividing into two. |
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Previous:
Back
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Book:
1001
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Section:
Human World
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Chapter:
Human Body: Systems
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