1. Cell Membrane

2. Phospholipid This is the main component of cell membranes.
Each phospholipid contains a polar head that is made up of phosphate and choline and it contains two nonpolar fatty acid tails.
All the non-polar tails turn towards one another in an attempt to exclude as much water as possible.

3. Phospholipid Bilayer
Oriented so that each layer has the hydrophobic tails facing each other to create a hydrophobic core.
Only allows some substances to diffuse through.
Cannot cross if charged or large in size.
Outer and inner layers are not symmetrical because each layer serves a different purpose.
Outer layer contains glycoproteins and glycolipids.
Not found in the inner layer.
Involved in cell recognition and cell-to-cell communication.
Outer layer also contains receptor proteins that bind hormones and growth factors.
Absent in the inner layer.
Inner layer specializes in binding elements of the cytoskeleton.

4. Integral Proteins Also known as intrinsic proteins.
At least one region imbedded within the hydrophobic core of the bilayer.
Most typical type are transmembrane proteins that span the entire bilayer.
Some are associated with one side of the membrane and do not span the entire membrane.

5. Peripheral Proteins Also known as extrinsic proteins.
Proteins that lie on and are secured to the inner or outer surface of the membrane.
They do not interact with the hydrophobic core of the bilayer.

6. Cholesterol
Play a role in providing the membrane with the proper amount of fluidity and stability.
At high temperatures, they reduce fluidity by restricting the movement of the phospholipids.
At low temperatures, they prevent the fatty acids from forming a non-fluid gel.
Has a hydrophilic end that associates with the non-polar section of the phospholipids.
Has a hydrophobic end that extends into the non-polar core of the phospholipid bilayer.
Not found in the cell membranes of plants or bacterial cells.

7. Glycolipid Phospholipid that contains a sugar chain on its surface.
Function as markers for cell recognition.
Examples: antigens that determine ABO blood types.
Provides a source of energy for the cell.

8. Oligosaccharide/ sugar chain
Short chain or branched chain of sugars that are attached to certain proteins and phospholipids of the membrane.
Only exists on the outside surface.

9. Glycoprotein Protein that contains a sugar chain on its surface.
Many different functions from structural components to receptors to enzymes.
The glycocalyx is the glycoprotein and polysaccharide covering that surrounds the cell membrane.

10. Transport Proteins
Used to help substances that can’t cross the lipid bilayer move across the membrane.
Some substance can’t cross because they are charged, too large, or both.
Used to facilitate transport and molecular active transport.

11. Attachment and Recognition Proteins
Proteins that are exposed on the intercellular and extracellular side of the membrane that can have attachment sites for different elements on either side of the membrane.
On the intracellular surface, they attach to various components of the cytoskeleton.
On the extracellular surface, they attach to various components of the extracellular matrix.
The ECM is secreted by cells and provides both structural and biochemical support for cells.
The ECM also includes elements needed for cell-to-cell recognition.

12. Receptor for signaling
Proteins that are receptors that can bind to hormones or growth factors.
When bound they can trigger a signal that begins a cascade of reactions within the cell.

13. Enzymatic Activities
Proteins involved in catalyzing biochemical reactions
Example: ATP synthases in the inner mitochondrial membrane.