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Chapter 5: Organizing Principles (Lipids, Membranes, Cell Compartments)…
Chapter 5: Organizing Principles (Lipids, Membranes, Cell Compartments)
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Phospholipids
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Lipid Rafts: Defined patches of sphingolipids and cholesterols (not randomly distributed as previously thought)
Cholesterol: Amphipathic, four carbon rings w/ hydrocarbon chain (-phobic), hydroxyl group (-philic)
At typical temperatures, cholesterol decreases membrane fluidity-ring structure interacts with fatty acid tails
At lower temperatures, increases membrane fluidity (prevents phospholipids from packing too tightly)
Proteins
Transporters: Move ions, etc. across membrane
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INTEGRAL (Cannot be separated from membrane) and PERIPHERAL (temporarily associated w/ membrane through noncovalent interactions) proteins
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Fluid Mosaic Model: Lipid bilayer is a fluid structure within which molecules move laterally, and is a mosaic of lipids and proteins
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Cell Organization
Eukaryotes
Lysosome: Have enzymes to break down proteins, nucleic acids, lipids, complex carbohydrates
Peroxisome: contains enzymes; involved in metabolic reactions- breakdown of fatty acids, synthesis of types of phospholipid
Golgi Apparatus: modifies proteins and lipids produced by ER; sorting station as they move to final destinations
3 Roles of Golgi: Further modifies lipids & proteins from ER, Acts as sorting station, site of most carbohydrate synthesis
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Cytoskeleton: Protein scaffold, network of tracks for movement of substances
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Endomembrane System: Includes the nuclear envelope, the endoplasmic reticulum, the Golgi apparatus, lysosomes, the plasma membrane, and the vesicles that move between them
Nucleus: Stores DNA, site of RNA synthesis
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Prokaryotes
No nucleus, smaller, different lipids in membranes
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Plasmid: in bacteria, small circular molecule of DNA- can replicate independently of bacterial genomic DNA
Pili, threadlike structures, can transfer plasmids between bacteria
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