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29 Cards in this Set
- Front
- Back
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what are the 4 main components of phophatidic acid? |
Glycerol 2 x fatty acid chains phosphate head group X |
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what is phosphatidic acid used for? |
its a little bit in membranes but MOSTLY for synthesis of phospholipids |
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at which carbon does the saturated and unsaturated chains attach to glycerol? |
C1-saturated C2-unstaurated C3-phosphate and head group |
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what is the key property of lipids? |
being amphipathic - both hydrophillic and phobic |
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what are phospholipids classified by? |
head group and acyl chain composition |
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name the five possible head groups for phosphoplipids, are they positive, negative or neutrally charged? |
ethanolamine -> Basic serine -> AA glycerol -> neutral inositol -> neutral choline -> Basic |
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name the backbone of sphingolipids and describe its structure |
sphingosine -> long chain amino alcohol, and just as glycerol derived lipids C2 and C3 are long fatty chains and C1 contains a head group |
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what are sphingolipids synthesised from? |
de novo (from new) from fatty acylCoA and serine |
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which phospholipids are similar in structure to spingolipids? |
phosphatidylcholine |
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name the five types of sphingolipid and their head groups. |
ceramide (no head group) sphingomyelin (phosphocholine) neutral glycolipid (glucose) lactosyl-ceramide (more than one saccharide) ganglioside (complex saccharide) |
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Where in the body is cholesterol synthesised and what is it synthesised from? |
every cell can create cholesterol -> from acetyl CoA. BUT about 25% is made in the liver |
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which organnelle does cholesterol synthesis occur in? |
in the cytosol and products are transferred to endoplasmic reticulum |
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describe the basic structure and properties of cholesterol |
planar topology, highly hydrophobic. A hydroxyl group makes it slightly ampiphilic. |
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what are the major structures of lipids determined by? |
their physical and chemical properties |
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name the two lipid structures that form spontaneously in solution and which lipids create them. |
micelles and liposomes, created from fats and detergents and phospholipids (due to relative shapes) fatty acids have tail and a bigger head but phospholipids have 2 tails and an equal head |
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name the five key features of the fluid-mosaic model of membranes |
1. the membrane comprises a bilayer of phospolipids 2. proteins are inserted into the sea of lipids 3. proteins either span the bilayer (integral) or reside within a leaflet 4. the membrane should be viewed as a fluid organelle 5. There is unrestricted motion of components |
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name the five properties of fluid mosaic membranes |
1. they are generally IMPERMEABLE to non-polar molecules and ions 2. membranes are FLEXIBLE and adapt as required by cells or organelles 3. DURABLE since they may encounter shear forces 4. membrane proteins carry out or regulate important biological functions 5. membrane lipids provide OMPTIMAL for the function of enzymes |
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Name five issues with the fluid mosaic model |
1. component lipids are heterogenous 2. protein insertion is heterogenous 3. leaflets are ASYMMETRIC 4. MOTIONAL RESTRICTIONS are upon components and proteins 5. membranes interact with CYTOSKELETON |
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name the main protein lipids and their proportion in membranes |
PC-phosphocholine PE-phosphoethanolamine ~20% SM- spingomyelin PS -phosphoserine ~8% cholesterol ~25% |
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what is the main purpose of phosphoserine in mebranes |
for signalling |
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what else plays a part in membranes aside from lipids and proteins? |
there is extensive glycosylation of lipids |
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which are the dominant fatty acid chains in membranes? |
C16 and C18 almost 50% are unsaturated |
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name four benefits of leaflet asymmetry |
1. head groups and lipid chains have distinct biophysical properties 2. creates membrane curvature 3. allows appropriate integration /association of membrane proteins 4. provides correct localisation of signalling molecules |
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describe the costs of leaflet asymmetry |
1. to create asymmetry proteins and energy must be used e.g. flippases, floppases and scramblases 2. disruption of asymmetry is used in cell process -> endo/exo cytosis and signalling |
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explain intra leaflet asymmetry (4 pts) |
- biomembranes create distinct MINI-DOMAINS known as LIPID RAFTS -> rich in cholesterol and sphingolipids with LONG acyl chains -> have a LIPID ORDERED PHASE -> they are Dynamic, Small and short-lived |
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describe some of the possible proteins in lipid rafts (2) |
-> caveolae proteins create an invagination of membrane -> GPI lipids anchor specific proteins to the membrane |
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explain why protein aggregation is useful (2) |
-used in signal pathways-> co-localisation -used for internalisation -> lysosomal degradation |
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Name the interactions that may be responsible for protein aggregation (4) and why they are ... |
1. protein-protein 2. protein-lipid 3. extracellular matrix 4. cytoskeleton effect the motion and localisation of the proteins |
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The lateral movement of proteins in membranes is NOT random. Describe what makes it so (4) |
1. proteins are transiently confined by obstacle clusters 2. proteins are transiently confined by the cytoskeleton 3. the cytoskeleton directs the motion of protein it is directly attached to 4. finally free and random diffusion in the membrane does happen |
