Download composition of the cell membrane and functions activity

Name: _________________
Date: ________
Composition of the Cell Membrane & Functions
Per. ___
The cell membrane is also called the plasma membrane and is made of a phospholipid bilayer. The
phospholipids have a hydrophilic (water attracting) head and two hydrophobic (water repelling) tails. The
head of a phospholipid is made of an alcohol and phosphate group, while the tails are chains of fatty
acids. Phospholipids can allow nonpolar molecules OR small molecules like water and oxygen to pass into or
out of the cell. This is known as simple diffusion because it does not require energy and the water or
molecules are moving with the concentration gradient. Concentration gradient- movement or spreading
of molecules from a crowded area to a less crowded area.
Some of the functions of the cell membrane include protecting and enclosing the cell, giving shape to the
cell, allowing transportation of materials in and out of the cell, and carrying out metabolic reactions near
the inner surface of the cell membrane.
SKETCH AND LABEL a phospholipid coloring the heads red and the tails blue.
label it (hydrophobic, hydrophilic, phosphate head, fatty acid tail, polar and non-polar)
PHOSPHOLIPID
Another type of lipid in the cell membrane is cholesterol that makes the membrane more fluid and adds
to its flexibility. Embedded in the phospholipid bilayer are proteins that also aid in diffusion and in cell
recognition. Large molecules like carbohydrates use transport proteins to help move across cell
membranes. Transport proteins go all the way through the bilayer and so are called integral proteins.
Peripheral proteins are found only on one side of the membrane and attach only temporarily, usually to
aid with a reaction within the cell. Some of the membrane proteins have carbohydrate chains called
glycoproteins, these proteins help with cell recognition. Some lipids also have carbohydrate chains
attached and are glycolipids, these also help with cell recognition.
Correctly color code and identify the name for each part of the cell membrane
Letter
Name/Color
Letter
_____
Phospholipid bilayer (no color)
_____
_____
Integral protein (pink)
_____
_____
Fatty acid tails (orange)
_____
_____
Phosphate heads (yellow)
_____
Name/Color
Peripheral protein (red)
Cholesterol (blue)
Glycoprotein (green)
Glycolipids (purple)
Match the cell membrane structure or its function with the correct letter from the cell membrane diagram. See in
the info on the first page for help.
Letter
Structure/Function
Letter
Structure/Function
Attracts water
_____
Repels water
_____
_____
_____
_____
Helps maintain flexibility of
membrane
Involved in cell-to-cell
recognition
_____
Make up the two layers
_____
Help transport certain materials
across the cell membrane
Also involved in cell to cell
recognition
Membrane Model Activity ANALYSIS
1. Why is the cell membrane described as being a bilayer?________________________________________
2. What is a phospholipid?__________________________________________________________________
3. What is the function of the cell membrane?
_____________________________________________________________________________________
4. Name three types of proteins embedded in the cell membrane and explain their function.
_____________________________________________________________________________________
_____________________________________________________________________________________
_____________________________________________________________________________________
5. Why do cells need energy to move some substances across the membrane?
_____________________________________________________________________________________
_____________________________________________________________________________________
6. When something moves with the concentration gradient it is called “passive transport”. Why do you think
it is called passive transport? (Do you think this requires an input of energy?)
_____________________________________________________________________________________
_____________________________________________________________________________________
7. When something moves against the concentration gradient it is called “active transport”. Why do you
think it is called active transport? (Do you think this requires an input of energy?)
_____________________________________________________________________________________
_____________________________________________________________________________________
8. What molecule provides the energy for Active Transport? ___________________________
9. How would water move through the cell membrane (i.e. would it flow through or use a protein, and which
protein would it use?) __________________________________________________________________
10. How do you think large molecules like glucose move through the cell membrane? _________________