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A scrap of onion skin sits under a microscope. It is made of tiny box-shaped parts called cells.

This is Chapter 2 in your NCERT Science book. It is called Cell: The Building Block of Life.

What you will learn

• Everything is made of them. Living things have one cell, or many. How to find a cell's size.
• Inside one cell. Working parts, each with its own job.
• The boundary decides. The membrane is the cell's edge. Water moves across it.
• A plant cell and an animal cell. Which parts each one has.
• Three kinds of plastid. Each has its own pigment and job.
• Two kinds of cell. DNA (the instructions) in a nucleus, or loose.
• How big a cell can get. The surface may be too small.
• One becomes two. Mitosis makes two cells. Meiosis makes four.
• When cells divide without control. Controlled growth, and cancer.

Need a quick recap?

These earlier lessons help. If a line ahead is unclear, open the one that covers it.

• A world below the eye — a lens finds tiny living things.
• Four kinds, not one word — bacteria, fungi, protozoa, viruses.
• More than one sign — living things share several signs, checked together.
• A plant makes its own food — nobody feeds a plant.
• Gaps between them — some things fit inside others.
• A scale is a ratio you can walk.
• Which count is the job asking for — square, or cube.