Another important property of the lipid bilayer is its fluidity. The lipid
bilayer contains lipid molecules, and, as we will discuss later, it also
contains proteins. The bilayer's fluidity allows these structures mobility
within the lipid bilayer. This fluidity is biologically important, influencing
membrane transport. Fluidity is dependent on both the specific structure of the
fatty acid chains and temperature (fluidity increases at lower temperatures).
Structurally, the lipid bilayer is asymmetrical: the lipid and protein
composition in each of the two layers is different.