A human red blood cell is about 8 micrometres wide. Roughly how many times wider is that than a plasma membrane?

1. A plasma membrane is 5 to 10 nm thick, and a red blood cell is approximately 8 micrometres wide. 2. Eight micrometres is 8,000 nanometres, and 8,000 divided by roughly 8 gives about 1,000. 3. So a red blood cell is approximately 1,000 times wider than a plasma membrane. 4. Ten or 100 times would put the membrane in the micrometre range, which light microscopy would then resolve, and it does not. _Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 5 "Structure and Function of Plasma Membranes", section 5.1 Components and Structure_