Unit 7 Study Guide
Terms in this set (23)
What happens when you drop oil in water?
Oil molecules are hydrophobic; oil molecules are non-polar and water is polar.
Phospholipids have what?
-Polar, phosphate-glycerol head. (hydrophilic)
-Non-polar, lipid tail (hydrophobic)
One way the tails can be removed from the water.
-Can flow past each other laterally, but not vertically.
Permanently embedded and go all the way through membrane (transmembrane); include protein channels.
Not fully embedded; attach to one surface of membrane.
Proteins with oligosaccharide chain attached (olgio- few; saccharide- sugars).
-Used for cell recognition by the immune system and as hormone receptors.
Roles of membrane proteins are:
Protein channels (facilitated) and protein pump (active).
Peptide-based hormones (insulin).
Cytoskeletal attachments and extracellular matrix
MHC proteins and antigens (immune recognition).
Tight junction and plasmodesmata.
Metabolic pathways (electron transport chain).
Binds phospholipids together; aids in packing phospholipids tightly and regulates the fluidity and flexibility of the membrane.
The cholesterol prevents rips in the membrane by holding the phospholipids together.
Cholesterol prevents the membrane from freezing solid by acting as a spacer.
Cholesterol in membrane fluidity:
1. Restricts movement of phospholipids and other molecules.
2. Disrupts packing of hydrocarbon tails of phospholipid molecules; flexibility.
3. Reduces permeability to hydrophilic/water soluble molecules and ions such as sodium and hydrogen.
Membranes are _______________ in which proteins move within the layers of __________.
"Fluid mosaics," lipids.
-PP bilayer is fluid.
-Proteins embedded are the mosaic.
-Membrane is dynamic and ever-changing.
Singer-Nicolson Fluid Mosaic Model
-PP create bilayer; PP are fluid, move laterally.
-Peripheral proteins are bound to inner or outer surface of membrane.
-Integral proteins permeate the surface of membrane.
-Membrane is a fluid mosaic of phospholipids and proteins.
-Proteins move laterally along membranes.
-Vary in size and shape.
-Unable to form periphery layer (no crossing).
-Proteins have hydrophobic regions.
Singer-Nicolson evidence (2)
(FLOURESCENT ANTIBODY TAGGING)
-Red/green markers on antibodies; fuse to proteins.
-Red cell + green cell.
-Cell fusion-> colors mix.
-Proteins lateral, not fixed.
Evidence: Electron micrograph where proteins are dark and phospholipids are clear.
-Lipid bilayer composed of phospholipids.
-Protein coat outer surface.
-Proteins do not permeate the lipid bilayer.
Why was the Davson-Danielli Model incorrect?
-Freeze fracture: breaking the membrane apart at weak point, middle of bilayer.
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