Chemistry of Life
Phospholipids
Proteins with carbohydrates (glycoproteins)
More information on glycoprotein and glycolipids that are produced at the Golgi apparatus.
Cholesterol
Cholesterol is a lipid with a hydrocarbon tail that is attached to a steroid and a hydroxyl (OH) group on the other end. Cholesterol is amphipathic, having a hydrophilic (OH end) and hydrophobic ends to the molecule.
The phosphate head of the molecule is negatively charged making it hydrophilic and the fatty acid end is non-polar so it is hydrophobic.
Structure and Function
The cell membrane (plasma membrane, or cytoplasmic membrane) is made up of phospholipids that forms the lipid bilayers and are embedded with, cholesterol, and proteins.The phospholipid bilayer provides selective permeability and fluidity to the membrane, allowing certain nonpolar molecules to pass through the membrane. By controlling the movement of substances that travel in and out the cell and organelles, the membrane protects the cell from its surroundings.
The outer surface of the cell membrane contains glycolipids and glycoproteins which create a unique surface for each type of cell allowing cells to recognize each other. The cell membrane also contains cholesterol which are located between the phospholipid tail and it is there to stabilize the membrane by decreasing the mobility of the phospholipids that it is attached to.
The different functions of proteins on the cell membrane
- Integral proteins are firmly attached to the membrane and functions as transport proteins as channels and carriers; enzymes or as receptors.
-Peripheral proteins are loosely bounded to the inside or the outside of the cell membrane and may include filaments. It functions as enzymes, motor proteins that changes shape during cell division or connect cells.
-Receptor Proteins on the surface of the cell membrane binds with signal molecules that would cause chemical change to the cell. It allow the cell to sense its surroundings by receiving messages from the environment.
