Term
| Properties of membranes (3) |
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Definition
1. Fluidity ie Not rigid
2. selective permeability
3. Responsivity (responsiveness to external/internal stimuli) |
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Term
| Functions of membranes (3) |
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Definition
1. Signal transduction
2. Import/Export molecules
3. Able to expand and retract in cell movement. |
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Term
| What is the major lipid component of membranes? |
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Definition
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Term
| Describe the structure of phosphodiacylglycerol. |
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Definition
2 FAs hydrophobic tails
(one tail is saturated; other tail contain at least a cis dlb. bond ie unstaturated)
Head group: polar/charged phosphate group |
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Term
| What makes diacylglycerols amphipathic? |
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Definition
| The polar/charged head group. |
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Term
| The charged/polar head groups can form what with water? |
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Definition
1. H-bonds OR
2. Electrostatic interactions |
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Term
| What properties of phospholipids allow spontaneous membrane formation? |
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Definition
| It is amphipathic (both polar and non-polar) |
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Term
| which one requires less energy to organize: Nonpolar groups OR water molecules? |
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Definition
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Term
| what is the difference between bilayer and micelle? |
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Definition
Bilayer --> forms as group of MULTI-TAILED phospholipids
Micelle --> SINGLE-TAILED phospholipids |
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Term
| Micelles, exported from hepatocytes, containing choles, phospholipids, and bile acids are store where? |
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Definition
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Term
| Initially phopholipids are added by ___ to what side? |
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Definition
| Added by SMOOTH ER to the CYTOSOLIC layer |
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Term
| What is the function of floppases/scramblase? |
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Definition
| Flip phospholipids from cytosolic side to LUMENAL (or EC space) side |
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Term
| What transport newly syn. bilayer to target membrane? |
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Definition
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Term
| What layer (cytosolic or lumenal) will face the EC space if transported to become the plasma membrane? |
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Definition
Lumenal layer
(Cytosolic layer will remain facing the cytosol regardless where it is transported) |
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Term
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Definition
| Flip phospholipids to cytosolic side |
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Term
| 2 Functions of flippases & Floppases AFTER membrane is formed. |
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Definition
1. Facilitates/prevent cell signaling
2. Contribuites to membrane polarity |
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Term
| What are the 4 main phospholipids? |
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Definition
1. phosphatidyl-ethanolamine
2. phosphatidyl-serine
3. phosphatidyl-choline
4. sphingomyelin |
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Term
| What is the only phospholipid that does not have a neutral charge? |
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Definition
| phosphatidylserine (neg. charge) |
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Term
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Definition
| On CYTOSOLIC monolayer of ER membrane |
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Term
| What are the 2 phospholipids that are predominantly on the cytosolic side? |
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Definition
1. phosphatidylserine
2. phosphatidylethanolamine |
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Term
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Definition
Type of floppase.
Translocate phospholipids to outer leaflet ie cytosolic to EC layer. |
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Term
| In Apoptosis, what phospholipid is translocated from cytosolic layer to EC layer? |
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Definition
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Term
| What signals for phagocytosis of cell by macrophages? |
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Definition
| Phosphatidylserine being on the cell surface = EC |
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Term
| What two events happens to signal apoptosis? |
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Definition
1. Activation of scramblase AND/OR
2. Inactivation o f phospholipids translocation (= "correcting" flipases) |
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Term
| What makes a membrane "gelled"? |
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Definition
1. High # of SATURATED lipid tails (ie Decrease # of dlb (cis) bonds)
2. More FAs hydrophobic bond formaiton
3. Low Temp
4. Low cholesterol conc. |
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Term
| Why does membrane need to be semi-fluid? |
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Definition
To allow:
1. lateral movement of proteins & lipids
2. diffusion of CO2 & O2
3. integral membrane (like transportors) to undergo conformational changes |
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Term
| Membrane fluidity depends on (4): |
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Definition
1. Lenght of acyl chains on membane lipids
2. # of dlb bonds in acyl chains (ie. # of unsaturation)
3. Amt of choles
4. Temp |
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Term
| What molecule provides OPTIMAL FLUIDITY and how? |
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Definition
Choesterol
1. provides stability
2. prevent crystallization of phospholipid hydrocarbon chains. |
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Term
| 4 important properties of glycolipids |
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Definition
1. Lipids thatcontians SUGAR
2. On EC monolayer
3. Self-associating (H-bond btw sugars)
4. Abundant in LIPID RAFTS |
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Term
| Where does glycolipid glycosylation takes place? |
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Definition
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Term
| 4 Functions of glycolipids |
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Definition
1. Protection against low pH & degradative enzymes
2. Cell-regonition involving lectins
3. Entry point of some bacterial toxin
4. Charged glycolipids |
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Term
| 2 functions of charged glycolipids (ex: gangliosides) |
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Definition
1. Alter electric field across membrane
2. Alter [ion]; esp Ca at membrane surface |
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Term
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Definition
| Membrane-bound carb-binding protein that binds the surgar group on glycolipids & glycoproteins --> result in cell-cell adhesion |
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Term
| ABO antigens are examples of what? |
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Definition
| Glycolipids & glycoproteins |
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Term
| The Fluid Mosaic is composed of ___ & ___. |
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Definition
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Term
| 3 contents of LIPIDS in fluid mosaic |
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Definition
1. phospholipids
2. glycolipids
3. cholesterol |
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Term
| 3 PROTEIN conents of fluid mosaic |
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Definition
1. integral membrane proteins
2. lipid linked proteins
3. periopherial proteins |
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Term
| How are lipid-linked membrane proteins linked to lipids membrane? |
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Definition
| 1. Covalently binds lipid chain (binds FA chain or prenyl group) 2. Anchored by oligosaccharide linker which is covalently linked to phosphatidylinositol of outer monolayer |
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Term
| Peripheral membrane proteins interact with other proteins through what type of bond formation? |
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Definition
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Term
| 4 types of integral membrane proteins |
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Definition
1. single alpha-helix
2. multiple alpha-helix
3. rolled up beta-sheet (beta barrel)
4. membrane spanning; anchored by amphipathic alpha helix |
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Term
| What is GPI and it's role? |
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Definition
GPI = glycosylphosphatidylinositol
1. In ER, transmembrane segment of protein is cleave --> give transmembrane protein + cleaved protein segment not free-floating in ER lumen.
2. GPI binds a lipid linker and the cleaved protein segment then binds GPI --> result in a lipid linked protein
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Term
| What 2 things cause the release of peripheral membrane proteins? |
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Definition
1. Extreme pH
2. Extreme ionic strenth |
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Term
| Oligosaccharide chains & disulfide bond have what kind of linkage and occurs on what side of the cell? |
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Definition
Covalent linkages;
outside of the cell |
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Term
| Where does glycosylation takes place? |
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Definition
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Term
| What protein structure level does disulfide bonds contribute to? |
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Definition
| Disulfide bonds contribute to tertiary protein structures. |
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Term
| 2 main molecules that makes up lipid rafts |
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Definition
1. sphingolipids
2. cholesterol |
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Term
| What makes up the strong attractive forces in lipid rafts? |
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Definition
| Interactions between long SATURATED fatty hydrocarbon chains --> result in THICKER membrane |
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Term
| How does a thicker membrane (lipid rafts) help the cell? |
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Definition
1. Can support/incorporate larger hydrophobic proteins
2. protein recruitment for vesicle formation
3. Recruitment of proteins for protein-protein interaction (ex: signal transduction from EC to IC) |
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