Cell Size and the Plasma Membrane

Why is the plasma membrane essential for a cell?

It acts as a "security gate," controlling what enters and exits the cell.

What is the plasma membrane primarily made of?

A phospholipid bilayer.

Why are cells so small? (Surface Area-to-Volume Ratio)

As a cell grows, its volume increases faster than its surface area, making material exchange inefficient.

What is the main consequence of a low surface area-to-volume ratio?

The cell cannot get materials (like oxygen) to its center quickly enough to survive.

Why are large organisms made of many small cells instead of one big one?

Many small cells have a high total surface area for efficient material exchange, served by a circulatory system.