Who proposed the fluid mosaic model?

$A$: $RBC$ membrane is highly flexible.
$R$: Amount of external protein in the cytoplasmic face of the membrane is more.

Biological membranes are composed of

Select the wrong statement regarding membrane channels.

Assertion : $A$ cell membrane shows fluid behaviour.
Reason : $A$ membrane is a mosaic or composite of diverse lipids and proteins.

The cell envelope is a chemically complex structure consisting of a tightly bound three-layered structure. Which layer is semi-permeable in nature?