The Plasma The Plasma MembraneMembrane
The Plasma MembraneThe Plasma Membrane
The cell membrane functions as a The cell membrane functions as a semi-permeable barrier: semi-permeable barrier: allows a few molecules to pass allows a few molecules to pass
through while preventing the passage through while preventing the passage of others either from the outside in or of others either from the outside in or from the inside outfrom the inside out
Membrane StructureMembrane Structure
The membrane is composed of a The membrane is composed of a phospholipid bilayerphospholipid bilayer
Structure of a phospholipid:Structure of a phospholipid: polar head polar head
hydrophilic (like water)hydrophilic (like water) two non-polar tails two non-polar tails
hydrophobic (fear water) hydrophobic (fear water)
PhospholipidsPhospholipids
Phospholipids are aligned tail to tail so Phospholipids are aligned tail to tail so that the non-polar areas form a that the non-polar areas form a hydrophobic region between the hydrophobic region between the hydrophilic heads on the inner and hydrophilic heads on the inner and outer surfaces of the membrane.outer surfaces of the membrane.
This layering is termed a bilayer and This layering is termed a bilayer and called a phospholipid bilayer in the case called a phospholipid bilayer in the case of the cell membraneof the cell membrane
The Fluid-Mosaic ModelThe Fluid-Mosaic Model
Fluid-mosaic model describes the Fluid-mosaic model describes the fluid nature of the membrane and fluid nature of the membrane and its compositionits composition
Fluid PortionFluid Portion Membrane behaves like a fluidMembrane behaves like a fluid
Due to the phospholipidsDue to the phospholipids Consistency ranges from oil to a gel like Consistency ranges from oil to a gel like
semi-solidsemi-solid animationanimation
The Fluid-Mosaic ModelThe Fluid-Mosaic Model
Mosaic PortionMosaic Portion Just like a piece of Just like a piece of
mosaic tile art, mosaic tile art, the membrane the membrane contains several contains several different different structures that structures that perform a variety perform a variety of functionsof functions
The Fluid-Mosaic ModelThe Fluid-Mosaic Model
Other structures found in the Other structures found in the membrane membrane Proteins:Proteins: involved in transporting involved in transporting
materials inside and out of the cellmaterials inside and out of the cell Carbohydrates:Carbohydrates:used to identify used to identify
substances that come in contact with substances that come in contact with the cellthe cell
Cholesterol:Cholesterol: a steroid used to help a steroid used to help stabilize the membranestabilize the membrane
The Fluid-Mosaic ModelThe Fluid-Mosaic Model