Lesson 8 of 13
How big a cell can get
Show on a big screenA block of paneer in hot gravy stayed cold in the middle. Cut into small cubes, the paneer got hot all through. Why?
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The rule
Heat gets in through the outside. Small cubes have more outside for each bit inside.
The surface is the outside of the cell. The inside is everything that needs feeding.
A cell takes in materials across its surface. Double the side, and the surface grows four times. The whole cell grows eight times. So a bigger cell has less surface for its inside.
So a bigger body has more cells, not larger ones.
Picture a cell as a cube of small blocks. A face is one flat side of one block.
Step 1 of 4
- A small cube, three blocks along each side.
- The blocks on the outside make a ring. One block is left in the middle.
- Double the side: six blocks along each edge now.
- The outside grows four times. All the blocks grow eight times.
Count the faces
| Side | Faces outside (6 × side × side) | Blocks in all (side × side × side) |
|---|---|---|
| 2 | 24 | 8 |
| 4 | 96 | 64 |
Side 2: 24 ÷ 8 = 3 faces for each block. Side 4: 96 ÷ 64 = 1.5 faces for each block.
Try the lab to finish this lesson.