What would best describe the structure of the plasma membrane? 1.rigid (not flexible)
2.gaseous
3.solid
4.fluid (flexible)

4. Fluid (Flexible)

Explanation:

Plasma membranes must be very flexible in order to allow certain cells, such as red blood cells and white blood cells, to change shape as they pass through narrow capillaries. The primary function of the plasma membrane is to protect the cell from its surroundings. Composed of a phospholipid bilayer with embedded proteins, the plasma membrane is selectively permeable to ions and organic molecules and regulates the movement of substances in and out of cells.

a physical change is being made.