Cell Size Limitations Chapter 8.2

Cell Size Limitations The cells that make up multicellular organisms come in a wide variety of sizes and shapes.

Considering this wide range of cell sizes… Why can’t most organisms be just 1 giant cell?

Diffusion limits cell size fast and efficient over short distances, slow and inefficient as the distances become larger.

DNA Limits Cell Size Cells need enough DNA to support the protein needs of the cell. In many large cells, more than one nucleus is present Amoeba

Large amounts of DNA ensure that cell activities are carried out quickly and efficiently.

Surface Area to Volume Ratio As a cell’s size increases, its volume increases much faster than its surface area.

If cell size doubled, the cell would require eight times more nutrients and would have eight time more waste to excrete. 2 mm 1 mm 2 mm 2 mm 1 mm 1 mm Surface Area= 6 mm2 Volume= 1 mm3 Ratio: 6:1 Surface Area= 24 mm2 Volume= 8 mm3 Ratio: 24:8 = 3:1

The surface area only increases by a factor of four. The cell would either starve or be poisoned from the buildup of waste products.