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CH 7 Membrane Structure, Function, and Use

CH 7 Membrane Structure, Function, and Use - Protobionts as...

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Protobionts as Cell Precursors? Protobionts Are aggregates of abiotically produced molecules surrounded by a membrane or membrane-like structure
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In earliest cell, the first genetic material Was probably RNA, not DNA (?) RNA can function as genetic code carrying material and sometimes as an enzyme (ribozymes) But we’ll save this topic for a different time
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Laboratory experiments demonstrate that protobionts Could have formed spontaneously from abiotically produced organic compounds For example, small membrane-bounded droplets called liposomes Can form when lipids or other organic molecules are added to water
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Liposomes have the same basic lipid bilayer composition as membranes 20 μ m (a) Simple reproduction. This lipo- some is “giving birth” to smaller liposomes (LM). (b) Simple metabolism. If enzymes—in this case, phosphorylase and amylase—are included in the solution from which the droplets self-assemble, some liposomes can carry out simple metabolic reactions and export the products. Glucose-phosphate Glucose-phosphate Phosphorylase Starch Amylase Maltose Maltose Phosphate Figure 26.4a, b
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Membrane Structure & Function
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Membrane Structure & Function Fluid mosaics of lipids and proteins Selectively permeable Transport mechanism Passive transport (uses Diffusion) Active transport (uses Energy) Bulk transport (endo- and exocytosis)
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Membrane is composed largely of a phospholipid bilayer Hydrophobic core of fatty acid tails (hydrocarbon)
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