ch. 8 membrane structure know: –structure of plasma membrane –phospholipids –integral proteins...
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Ch. 8 Membrane StructureCh. 8 Membrane Structure
Know:Know:– Structure of plasma membraneStructure of plasma membrane– PhospholipidsPhospholipids– Integral proteinsIntegral proteins– Peripheral proteinsPeripheral proteins– CholesterolCholesterol– GlycoproteinsGlycoproteins– GlycolipidsGlycolipids– OligosaccharidesOligosaccharides– Functions of membrane proteinsFunctions of membrane proteins
Phospholipid StructurePhospholipid Structure
Phospholipid Bilayer – held together Phospholipid Bilayer – held together by hydrophobic interactionsby hydrophobic interactions
Membranes are fluid – they are not Membranes are fluid – they are not staticstatic
Factors that affect membrane Factors that affect membrane fluidityfluidity
1.1. Unsaturated fatty acid chains – increase Unsaturated fatty acid chains – increase fluidity due to the chains not packing wellfluidity due to the chains not packing well
2.2. Temperature – low temperatures can decrease Temperature – low temperatures can decrease fluidity when phospholipids settle into a tightly fluidity when phospholipids settle into a tightly packed arrangementpacked arrangement
3.3. Cholesterol – packed in between phosholipidsCholesterol – packed in between phosholipids• High temp. – disrupts movement of phospholipids, High temp. – disrupts movement of phospholipids,
decreases fluiditydecreases fluidity• Low temp. – does not allow phospholipids to pack Low temp. – does not allow phospholipids to pack
together, increases fluiditytogether, increases fluidity
CholesterolCholesterol
Fluid Mosaic ModelFluid Mosaic Model
Membrane structure videoMembrane structure video
Have distinct inside and outside faces Have distinct inside and outside faces (amphipathic)(amphipathic)Proteins dispersed and embedded throughout Proteins dispersed and embedded throughout phospholipids bi-layer (membrane)phospholipids bi-layer (membrane)
2 types of proteins present in membrane:
-Integral proteins-Peripheral proteins
Membrane ProteinsMembrane Proteins
Integral ProteinsIntegral Proteins
Can be:Can be:– Transmembrane- has Transmembrane- has
hydrophobic midsections hydrophobic midsections between hydrophilic ends between hydrophilic ends exposed on each side of exposed on each side of membranemembrane
– Unilateral- reaching only Unilateral- reaching only partway across the membranepartway across the membrane
•Definition-inserted into the membrane, hydrophobic regions are surrounded by hydrocarbon portions of phospholipids
Peripheral ProteinsPeripheral Proteins
Definition: Not embedded but Definition: Not embedded but attached to membrane’s attached to membrane’s surface, can be attached to surface, can be attached to integral proteins of filaments integral proteins of filaments of cytoskeletonof cytoskeleton
Inside and Outside facesInside and Outside faces
Synthesis and modification of the plasma Synthesis and modification of the plasma membrane by the ER and the golgi membrane by the ER and the golgi apparatus determines the asymmetric apparatus determines the asymmetric distribution of lipids, proteins and distribution of lipids, proteins and carbohydratescarbohydrates
Carbs are restricted to the exterior of the Carbs are restricted to the exterior of the membranemembrane
Sidedness of the plasma membrane Sidedness of the plasma membrane – look at Fig. 8.8 in book– look at Fig. 8.8 in book
Proteins on the inside Proteins on the inside of the vesicle become of the vesicle become proteins on the proteins on the outside face of the outside face of the cell membranecell membrane
TransportTransport
Serves as a passage way for certain moleculesServes as a passage way for certain molecules
Enzymatic ActivityEnzymatic Activity
Active sites on interior Active sites on interior surface which surface which catalyze reactions catalyze reactions inside cellsinside cells
Signal TransductionSignal Transduction
Docking sites for Docking sites for chemical chemical messengers that messengers that will cause a change will cause a change in protein shape in protein shape and relays a and relays a message to the cellmessage to the cell
Intercellular joiningIntercellular joining
Proteins on adjacent cells can hook togetherProteins on adjacent cells can hook together
Cell-to-Cell RecognitionCell-to-Cell Recognition
Glycoproteins serve Glycoproteins serve as identification tags as identification tags which are recognized which are recognized by other cellsby other cells
Attachment to CytoskeletonAttachment to Cytoskeletonand ECM and ECM
ECM- extracellular ECM- extracellular matrixmatrix
Helps maintain cell Helps maintain cell shape and fixes shape and fixes location of membrane location of membrane proteinsproteins
Membrane 2 videoMembrane 2 video
Helpful Video?Helpful Video?
http://www.5min.com/Video/Proteins-as-http://www.5min.com/Video/Proteins-as-the-Mosaic-of-the-Cell-Membrane-the-Mosaic-of-the-Cell-Membrane-150624158150624158