lession1 细胞膜

When dissolved in water, phospholipids self-assemble into a bilayer structure.
It is remarkable that something as organized as the plasma membrane
is primarily driven by spontaneous self-assembly.
It is not made by somehow being put together on a factory floor
before being delivered to the edge of the cell.
This is one of the nicest ways to underscore
the importance of self-assembly phenomena, the ability
of a well-organized and quite complex structure
to arise simply based on the chemistry of individual components.
In a lipid bilayer, there is also dynamic diffusion of the lipids
and other membrane components within the two-dimensional plane of the bilayer.
This lateral diffusion gives the membrane its fluid structure.
A fluorescence photobleaching experiment readily proves this concept,
showing that the fluorescence from a particular region of a fluorescently
labeled membrane can recover after the region is bleached by a laser beam.
Fluorescent membrane lipids or other components diffuse into the region,
and bleached membrane lipids or components
diffuse out of the region over time.
This is where the fluorescence recovery occurs.
And this is why the method is called FRAP or FRAP,
Fluorescence Recovery After Photobleaching.
Biological membranes are composed of more than just phospholipids.
They also contain many different types of membrane proteins
that are associated in different ways with a lipid bilayer.
These membrane proteins carry out many critical functions,
facilitating the dynamic processes that occur at the membrane