Video Transcript
Which of the following is true
about the cell membrane? (A) It has a solid nature. (B) It has a dry nature. (C) It has a fluid nature. Or (D) it has a gaseous nature.
The cell membrane is responsible
for separating the cell’s internal environment from the external environment. It is composed of two layers of
phospholipids. This is called a phospholipid
bilayer, since bi- means two. Each phospholipid has a hydrophilic
phosphate head. These heads face the outer and
inner surfaces of the membrane. The other part of the phospholipid
is a hydrophobic tail made of fatty acids that face toward the inner core of the
membrane. This creates a thick hydrophobic
layer in the membrane that it is difficult for hydrophilic substances in the aqueous
solution to pass through.
Embedded within the phospholipid
bilayer are a number of other molecules and proteins that also affect the structure
and function of the membrane. Some proteins function to allow
certain hydrophilic molecules to pass through the membrane. And others provide identification
markers on the cell surface. Also, there are cholesterol
molecules between the phospholipids that help keep the bilayer from becoming either
too stiff or too fluid.
All of the components of the cell
membrane are able to move freely around one another and are held together by
attractive forces, rather than by chemical bonds. The cell membrane structure is in
fact referred to as a fluid mosaic, as it is made up of many types of parts that
move freely around each other. Therefore, the correct answer to
this question is (C). The cell membrane has a fluid
nature.
