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35 Cards in this Set
- Front
- Back
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Fatty acids |
-unsaturated -one or more double bonds -monounsaturated -one double bond -polyunsaturated - more than one Component of all membrane lipids (except sterols) |
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Hydrolysis |
removes fatty acids from glycerol |
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Phospholipids |
amphipathic - polar/charged nitrogen attached to phosphate group -Hydrophobic (non-polar) and hydrophilic ends |
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steroids - sterols |
provide support/stability |
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3 ways for lipid transfer |
1. lateral diffusion 2. vesicle transport 3. lipid exchange |
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How could you track a protein moving through a cell? |
Would need: -a cell making proteins -a way to visualize the cell -a way to label and see the newly made proteins |
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protein sorting signals |
-short amino acid sequence -part of the polypeptide -must be created during translation |
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what parts of the cell will have an ER signal peptide? |
-a functioning polypeptide in the ER, Golgi, lysosome, vacuole, or plasma membrane - will have this sorting signal |
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post translational translocation |
-protein released from ribosome after translation -completed protein diffuses to the appropriate membrane and associates with the translocation apparatus |
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co-translation translocation |
the nascent protein may associate with the translocation apparatus while it is till being synthesized on the ribosome |
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Transmembrane proteins |
-span the membrane -large hydrophobic region -once membrane proteins have been embedded in the lipid bilayer, it can be transported to other membranes |
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Role Glycosylation in ER lumen |
-sorting signal for lysosome -may be required to alter protein structure, complete its folding -may make protein more stable |
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two ways for second step in protein transport |
-protein is embedded in membrane - transported to other membranes OR -protein released into ER lumen |
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ER membrane proteins |
-cargo receptors -v - snares -(v-vesicle) |
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Target destination proteins |
-t-snares -(t-target) |
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Protein sorting to non-endomembrane locations |
-nucleus, peroxisomes, mitochondria and chloroplasts -each organelle has a specific peptide sorting signal (different from eachother) -transport occurs post translationally in cytosol |
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Membranes |
-define boundaries -serve as permeability barriers -sites of specific proteins and functions |
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Membrane components |
-lipids -proteins -carbohydrates |
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Leaklet |
half of a phospholipid bilayer -cytosolic leaflet and extracellular leaflet |
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Fluid mosaic model |
Singer and Nicolson, 1972 -fluid: lipids and proteins can move -mosaic: lipid, protein, carbohyhdrates |
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Types of phospholipid movement within monolayer
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-rotation -lateral diffusion -rapid + random |
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Transverse lipid movements |
-scramblase: move phospholipids along concentration gradient - no ATP -flippase and floppase: move lipids against gradient - Require ATP |
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Tm |
Transition temperature Tm -phase transition -below the Tm, any functions that rely membrane fluidity will be disrupted |
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how does fatty composition affect membrane fluidity |
-length of chains (longer - high Tm), (short - low Tm) -degree of saturation |
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how do sterols affect membrane fluidity
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rigid cholesterol - decreases fluidity and increases Tm -prevents tight packing of hydrocarbon chains of phospholipids - reduces tendency of membranes to gel -FLUIDITY BUFFER |
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What other effects do sterols have on membranes |
-decrease the permeability -fill spaces between hydrocarbon chains of phospholipids -blocks the routes that ions and small molecules would take through the membrane |
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Lipid rafts |
-membrane microdomains -stable and stay clustered together as a unit -distinctive regions of phospholipids enriched in sterols and membrane proteins |
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Evidence for mosaic of proteins achieved how? |
Freeze - fracturing -bilayer or membrane frozen/hit sharply |
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what affects a membranes permeability? |
-lipid bilayers: highly selective -selective permeability: some substances cross a membrane more easily than others |
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why do molecules move across membranes? |
-Diffusion: ions or molecules in solution from -Osmosis:water (from a region of low concentration to high solute concentration) |
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Chemical vs. Electrochemical gradient |
Chemical gradient - a higher glucose concentration outside the cell Electrochemical gradient - more positice charges outside the cell and a higher Na+ concentration outside the cell |
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Importance of ion electrochemical gradients |
-many types of ion pumps found in plasma membranes of organelles -play the primary role - formation and maintenance of ion gradients -transport of ions against their gradient |
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Channel and transporter proteins |
Passive transport: diffusion and facilitated diffusion Active transport |
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Channel proteins |
make lipid bilayers permeable to ions or molecules
-different type -Structure: pore lined with polar amino acids, outside of channel lined with hydrophobic groups to interact with lipid bilayer |
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Transporter proteins |
Facilitated + transport Proteins that change shape during transport across lipid bilayer: conformational change -slower than channel |
