IB Biology B2.3 Notes

Now that you know about cell specialization, you are expected to understand the several adaptations cells develop to better perform their function. This begins with adaptations for an increased surface-to-volume ratio. This is typically done by:

1. Reducing cell diameter
2. Flattening or elongating the cell
3. Making large membrane invaginations
4. Forming hair-like structures called microvilli

Using this, cells shaped like or cylinder with microvilli or invaginations will have a greater surface area than a sphere of the corresponding volume. Two examples you need to remember are:

1. The microvilli contained in luminal cells of the proximal convoluted tubule. These maximize surface area for efficient diffusion of substances whilst maintaining cell shape to form a tube.
2. The flattened disc shape of erythrocytes with a large invagination on either side. This increases surface area for oxygen to diffuse and bind to haemoglobin.