3. > The cell is the smallest unit of life classified as a living thing.
> It is the structure of all living things on earth.
> We will focus on the structure of the plasma membrane of the
cell and some of its basic functions.
4. > The plasma membrane is a thin membrane that surrounds and defines the
boundaries of all living cells.
> It consists of a double layer, also know as the bilayer, of phospholipids with
various proteins attached to it.
> Cell membranes define and compartmentalize space, regulate the flow of
materials, detect external signals, and mediate interactions between cells.
5. PROTEINS IN THE CELL PLASMA
MEMBRANE
> In the plasma membrane we have peripheral proteins and integral proteins.
> Integral proteins penetrate the bilayer from the extracellular fluid to the cytoplasm.
> Peripheral proteins are attached to the integral proteins and don’t cross the
membrane.
6. The plasma membrane acts as a barrier and separates the outside
of the cell from the inside.
It is selectively permeable to ions and inorganic molecules,
meaning it controls the movement of molecules in and out of the
cell.
7. >The plasma membrane is mainly composed of
phospholipids.
>The polar heads are hydrophilic and the nonpolar tails
are hydrophobic.
8. Cholesterol helps maintain the integrity of the membranes and plays an
important role in facilitating cell signaling so that the cells can communicate
with each other.
10. Quiz
Time
A B C D
E
F
First: Draw your own plasma membrane
Second: Label Letters A-F, for B and C what type of proteins are
they?
Third: For letter E state the hydrophobic and hydrophilic sections.
Fourth: State where the cytoplasm and the extracellular fluid are
11. > This website is a great place for students who are
interested in looking at the plasma membrane in more
detail.
http://www.bio.davidson.edu/people/macampbell/111/memb-
swf/membranes.swf
Further Information
Editor's Notes
We will learn about the basic structure of the plasma membrane.
Before we move on, students should write down what this quote means to them and why this is important. (There is no wrong answer)
Questions: 1) Why do you think the plasma membrane is important to the cell?
2) Can you think of a few functions of plasma membrane?
Have students draw their own plasma membrane to better understand its structure.
