Cell Membrane & Tonicity
Worksheet
Composition of the Cell Membrane & Functions
The cell membrane is also called the PLASMA membrane and is made of a
phospholipid BI-LAYER. The phospholipids have a hydrophilic (water
attracting) HEADS and two hydrophobic (water repelling) TAILS. The head
of a phospholipid is made of an alcohol and GLYCEROL group, while the
tails are chains of FATTY ACIDS. Phospholipids can move SIDEWAYS and
allow water and other NON-POLAR molecules to pass through into or out of
the cell. This is known as simple PASSIVE TRANSPORT because it does
not require ENERGY and the water or molecules are moving WITH the
concentration gradient.
SKETCH AND
LABEL a
phospholipid
coloring the
heads red and the
tails blue.
Another type of lipid in the cell membrane is CHOLESTEROL that makes the membrane
more fluid. Embedded in the phospholipid bilayer are PROTEINS that also aid in diffusion
and in cell recognition. Proteins called INTEGRAL proteins go all the way through the
bilayer, while PERIPHERAL proteins are only on one side. Large molecules like
PROTEINS or carbohydrates use proteins to help move across cell membranes. Some of
the membrane proteins have carbohydrate PARTS attached to help cells in recognize
each other and certain molecules.
List 4 functions of the cell or plasma membrane:
a. CELL SIGNALING
b. SELECTIVE TRANSPORT
c. EXCRETION OF WASTES
d. STRUCTURAL SUPPORT
Correctly color code and identify the name for each part of the cell membrane.
Letter Name/Color Letter
Name/
Color
__ A ___
Phospholipid bilayer (no
color) __ H ___
Peripheral protein
(red)
__ B ___ Integral protein (pink) __ I ____ Cholesterol (blue)
__ F ___ Fatty acid tails (orange) __ C___
Glycoprotein
(green)
__ G ___ Phosphate heads (yellow) __ E ___ Glycolipids (purple)
Match the cell membrane structure or its function with the correct letter from the cell membrane diagram.
Letter Structure/Function
Lette
r Structure/Function
__ G ___ Attracts water __ F__ Repels water
__ I ___
Helps maintain flexibility of
membrane _G&F Make up the bilayer
