Cell — Science definition

Defined in 2 courses:

Where it is taught

In use

The name has stuck for three and a half centuries, even though the thing Hooke was looking at was dead — cork is bark, and what he saw were the stiff leftover cell walls, made of a tough material called cellulose, that plants build on the outside of their cells.

Cell Theory & Discovering Cells

Then in 1855 the physician Rudolf Virchow supplied the missing piece with a phrase that became famous — omnis cellula e cellula, 'every cell from a cell.

Cell Theory & the Discovery of Cells

Questions using cell

Problem 1

Does cell theory require every organism to have many cells?
Answer and explanation

No. A single cell can be an organism; many organisms contain multiple cells.

Problem 2

Why is cork a limited model of a living cell?
Answer and explanation

Much of the living content is absent; the observed compartments mainly show remaining cell walls.

Problem 3

What other information is needed to infer mass from cell count?
Answer and explanation

Cell sizes and composition matter. More cells do not supply a complete mass measurement by themselves.

Problem 4

Illustrative record: a living cell divides into two cells; each later divides once. A student claims the resulting four cells must be four times the original mass. Use cell theory to explain the number change and evaluate the mass claim.
Answer and explanation

The sequence fits new cells arising from existing cells and gives four cells after the two division rounds. The mass claim is unsupported: cells can differ in size, and growth requires material uptake. Cell count alone does not establish four times the starting mass. Additional mass or size observations would be needed.

Count one to two to four cells.

Connect new cells with previous cells dividing.

Distinguish cell production from total mass.

Response criteria

  • Explain the relevant biological process accurately.
  • Use the supplied evidence and show calculation steps with units where needed.
  • Connect a labeled model or mechanism with the claim.
  • State an assumption, evidence limitation, or useful next observation.

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