All
____________________
cells
and
many
of
the
tiny
organelles
internal
to
cells
are
bounded
by
thin
membranes
.
These
____________________
are
composed
primarily
of
____________________
and
proteins
and
are
typically
described
as
phospholipid
bi
-
____________________
.
Cell
membranes
also
contain
____________________
in
the
phospholipid
____________________
.
In
some
____________________
there
are
only
a
few
cholesterol
molecules
,
but
in
others
there
are
as
many
cholesterols
as
phospholipids
according
to
Audesirk
&
Audesirk
.
Cholesterol
makes
the
bilayer
stronger
,
more
flexible
but
less
fluid
,
and
less
____________________
to
water
-
soluble
substances
such
as
ions
and
monosaccharides
.
