Cells: the tiny building blocks of life
Every living thing is made of tiny cells. What is inside them, how plant and animal cells differ, and how you grow. With a cell-in-a-bag model.
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All living things are made of tiny building blocks called cells. Some living things are only one cell. You are made of lots and lots of them![1][5]
Cells are so small that you cannot see them with just your eyes. Scientists use a microscope, which makes things look much bigger.[1]
Your body has many kinds of cells, like bone cells, fat cells and nerve cells. Each kind has its own job.[5]
Every cell has a thin skin around it, called the membrane. It lets things in and out. Many cells have a control centre inside, called the nucleus.[3]
Plant cells also have a strong wall around them, and green parts that use sunlight to make food. Animal cells have no wall.[3]
New cells come from old cells: a cell can split to make new cells. That is how you grow, and your body makes new cells every day.[1][5]
Try it: A cell in a bag
You need
- Two clear zip-lock bags
- Water
- Two ping-pong balls or two big grapes
- A handful of green peas or green buttons
- A small cardboard box or plastic tub that one bag fits into
- Paper towels
Safety
Do not eat the peas or grapes used in the model. Close the bags well and do the activity on a tray; mop up spilled water so nobody slips.
What to do
- Fill both bags about half full with water. Close them tightly.
- Open one bag a little, drop in a ping-pong ball and close it again. This is your animal cell.
- Put a ping-pong ball and the green peas in the second bag and close it.
- Put the second bag inside the box. This is your plant cell.
- Gently press both cells. Which one keeps its shape better? Name each part: skin, jelly, control centre, wall, green food-makers.
What happens, and why?
The bag is like the cell's thin skin (membrane), the water is like the jelly inside (cytoplasm) and the ball is like the control centre (nucleus). The plant cell also has a strong wall, like the box, and green parts that make food from sunlight, like the peas.[3]
Play: Made of cells?
Is it a living thing made of cells, or something that is not alive? Pick the right box.
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Quiz
Other ages: Ages 10–11 · Ages 15–16