the.com/membrane
the bouncer of biology, deciding who gets in and who waits outside forever
means A thin, flexible sheet of tissue or material that lines, separates, or covers something — letting certain things pass while blocking others.
from From Latin 'membrana,' meaning skin or parchment, especially the thin skin that covers the organs of the body. It comes from 'membrum,' meaning a limb or member — so a membrane was, in a sense, the skin belonging to a body part. The same Latin 'membrana' was also the word for the prepared animal skin used as writing material, which is why the word carries that papery, sheet-like sense to this day.
- thinness
- Cell membranes are about 5 nanometers thick
- self-healing
- Punctured membranes reseal themselves within seconds
- fluid mosaic
- It flows like oil, not a solid wall
- voltage
- Neuron membranes hold charge like tiny batteries
- ancient design
- Lipid bilayers predate the first true cells
blood-brain barrier — selective barrier in brain capillaries that blocks ~98% of large molecules from entering cerebrospinal fluid
cell membrane — phospholipid bilayer discovered by singer and nicolson in 1972, controls all substance entry/exit
myelin sheath — insulating membrane wrapping around axons that increases nerve signal speed up to 100x in the spinal cord