The gate with tiny gaps

The idea

The cell membrane encloses the cytoplasm and nucleus and separates one cell from another; it is porous, letting in materials essential for life processes and letting out waste.

A cell must breathe and clear out

A cell needs materials to stay alive, and it makes waste. Both must cross its outer layer, the cell membrane.

What kind of outer layer would let this happen?

• A fully sealed layer with no gaps
• A layer with tiny gaps, like a sieve
• No layer at all

At the membrane

Each thing arrives at the membrane. Decide: does the cell let it in, or send it out?

Porous, and a wall between cells

The cell membrane encloses the cytoplasm and nucleus and separates one cell from another. It is porous: it lets in materials essential for life processes and lets out waste.

Porous means it has tiny gaps for things to pass through. Each cell has its own membrane.

Notes

The cell membrane encloses the cytoplasm and nucleus, separates one cell from another, and is porous: it lets in what the cell needs for life and lets out waste.

Check yourself

What does the cell membrane do?

Two cells sit side by side. What separates one cell from the other?

A cell makes waste. How does the waste leave the cell?

• Lets in materials essential for life processes and lets out waste. — correct. Yes. That is why it is called porous: it has tiny gaps for things to pass.
• Regulates everything the cell does.. That is the job of the nucleus.
• Keeps everything out so nothing can enter.. A cell would die. It must take in materials and get rid of waste.
• The nucleus. The nucleus is inside each cell, in the middle.
• The cell membrane — correct. Yes. Each cell is enclosed by its own membrane, which separates it from the next cell.
• The cytoplasm. The cytoplasm is inside the membrane. It is the filling.
• It goes out through the porous cell membrane. — correct. Yes. The membrane lets waste out.
• It stays inside forever.. Waste has to leave. The membrane lets it go out.
• It goes out through the nucleus.. The nucleus is inside the cell. It regulates activities; it is not the exit.