ap biology 2007-2008 the cell membrane ap biology membrane function outer plasma membrane forms a...
TRANSCRIPT
AP Biology
Membrane FunctionMembrane Function
Outer plasma membraneOuter plasma membrane Forms a boundary between a living cell and Forms a boundary between a living cell and
its surroundings (prok and euk cells)its surroundings (prok and euk cells) Exhibits selective permeabilityExhibits selective permeability
Controls traffic of molecules in and outControls traffic of molecules in and out
Internal organelle membranesInternal organelle membranes Form boundary for the organellesForm boundary for the organelles Compartmentalize chemical reactionsCompartmentalize chemical reactions
AP Biology
Parts of the Plasma Membrane
Glycerol Backbone
Two Fatty Acid Chains
Phosphate Group
Phospholipids are the main component of a plasma membrane.
They are lipids made of a phosphate molecule, a glycerol molecule, and two fatty acid chains.
AP Biology
The head of the phospholipid molecule is attracted to water, whereas, the glycerol and two fatty acid tails
are repelled by water.
POLAR, and water-loving or attracted to water
NON-POLAR, and water-fearing or repelled by water
hydrophilic
hydrophobic
AP Biology
Membrane StructureMembrane Structure
All membranes are All membranes are phospholipid bilayersphospholipid bilayers with embedded proteins.with embedded proteins.
Label the:
Hydrophilic heads
Hydrophobic tails
OUTSIDE CELL
INSIDE CELL
PLASMA
MEMBRANE
AP Biology
A membrane is a mosaicA membrane is a mosaic Proteins and other molecules are embedded in Proteins and other molecules are embedded in
a framework of phospholipidsa framework of phospholipids
A membrane is fluidA membrane is fluid Most protein and phospholipid molecules can Most protein and phospholipid molecules can
move laterallymove laterally
AP Biology
Glycoproteins and glycolipids are Glycoproteins and glycolipids are proteins and lipids with short chain proteins and lipids with short chain
carbohydrates attached on the carbohydrates attached on the extracellularextracellular side of the membrane. side of the membrane.
These carbohydrate chains act as antennae, receiving chemical messages from other cells. They are also
markers & identifiers that identify the cell to other cells.
AP Biology
The cholesterol prevents the fatty acid chains of the phospholipids from sticking together.
CholesterolMolecule
PLASMA MEMBRANE
Cholesterol molecules are found throughout the plasma membrane.
AP Biology
Embedded in the bilayer are proteinsEmbedded in the bilayer are proteins
Most of the membrane’s functions Most of the membrane’s functions are accomplished by the embedded are accomplished by the embedded
proteins. proteins. Integral proteinsIntegral proteins implanted in the implanted in the
membrane- partway or all the way acrossmembrane- partway or all the way across Peripheral proteinsPeripheral proteins are on one side or the are on one side or the
other of the membraneother of the membrane
Parts of the Plasma Membrane
AP Biology
Peripheral ProteinsPeripheral Proteins
Types of Membrane ProteinsTypes of Membrane Proteins
1.1. Recognition proteinsRecognition proteins2.2. IntegrinsIntegrins3.3. Cell junction proteinsCell junction proteins4.4. Enzymes Enzymes 5.5. Receptor proteins Receptor proteins 6.6. Transport proteinsTransport proteins
– Passive and activePassive and active
AP Biology
Adhesion ProteinsAdhesion Proteins
- IntegralIntegral
- Help cells of the same type stick together Help cells of the same type stick together in a tissue.in a tissue.
AP Biology
Communication ProteinsCommunication Proteins
- IntegralIntegral
- Match with an identical protein on another Match with an identical protein on another cell and form a channel, which directly cell and form a channel, which directly connects two cell’s cytoplasmconnects two cell’s cytoplasm
- Chemical signals flow through the Chemical signals flow through the channels.channels.
AP Biology
Receptor proteinsReceptor proteins
- bind hormones and other substances on - bind hormones and other substances on the outside of the cell.the outside of the cell. Binding triggers a change inside the cell.Binding triggers a change inside the cell.
Called signal transductionCalled signal transduction Example: The binding of insulin to insulin Example: The binding of insulin to insulin
receptors causes the cell to let glucose receptors causes the cell to let glucose transport into the cell.transport into the cell.
AP Biology
Recognition ProteinsRecognition Proteins
- identify type of cell - identify type of cell andand identify a cell as identify a cell as “self” versus foreign“self” versus foreign Most are glycoproteins Most are glycoproteins
Carbohydrate chains vary between species, Carbohydrate chains vary between species, individuals, and even between cell types in a individuals, and even between cell types in a given individual.given individual.
Glycolipids also play a role in cell recognitionGlycolipids also play a role in cell recognition
AP Biology
Many membrane proteins are Many membrane proteins are enzymesenzymes This is especially important This is especially important on the membranes of organelles.on the membranes of organelles.
AP Biology
Transport ProteinsTransport Proteins Passive Transport ProteinsPassive Transport Proteins
allow water soluble substances (small allow water soluble substances (small polar molecules and ions) to pass polar molecules and ions) to pass through the membrane without any through the membrane without any energy costenergy cost
Active Transport ProteinsActive Transport Proteins The cell expends energy to transport The cell expends energy to transport
water soluble substances water soluble substances againstagainst their their concentration gradientconcentration gradient