Lecture14 - Lecture 14 Bioenergetics and Enzymes Roles of...

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Lecture 14: Bioenergetics and Enzymes                                                                                                October 25, 2007 Roles of Cells  move (muscle contraction)  sensory transduction (see, hear, touch)  DNA replication— make proteins  packaging (neurotransmitters, vesicles)  synapse— generate electrical signals  doing work requires energy  order requires an input of energy First Law of Thermodynamics Energy cannot be created nor destroyed, but can be converted Metabolic reactions  in cells convert energy from one form to another Some cell energy transformations:  mitochondria: acetylCoA  ATP  muscle: mechanical energy due to actin/myosin  nerve cells: ATP  chemical potential gradient Second Law of Thermodynamics Process can only occur spontaneously if the reaction increases the disorder of the system (ΔG<0) catabolism and anabolism together constitute the cell’s metabolism catabolic pathways  (use energy) lose energy as heat (ΔG<0) anabolic pathways  (build up energy) require energy (ΔG>0) an unfavorable reaction can occur if linked to one with an even  greater negative ΔG (net effect is ΔG<0) Oxidation and Reduction —moving electrons from one molecule to another cells obtain energy by the  oxidation  of organic molecules reduction - atom becomes more negative (gains electrons)   Hydrogenation = Reduction a molecule can add an electron and a proton together in hydrogenation/reduction reaction (# of  C-H bonds increases) A + e -  + H +    AH (hydrogenation/reduction) oxidation - atom becomes more positive (loses electrons)  oxidation of methane to CO 2  is energetically favorable(covalent hydrogen bonds are replaced with  oxygen atoms— dehydrogenation)  number of C-H bonds decreases during oxidation Page 1 of 5
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Lecture 14: Bioenergetics and Enzymes                                                                                                October 25, 2007 Hydrolysis — a covalent bond is split by adding water  large molecule + water   small molecule  -ΔG, but needs an enzyme  how you get energy from high-energy bonds Equilibrium balance between concentration gradient and intrinsic energy of molecule such that for the reaction 
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Lecture14 - Lecture 14 Bioenergetics and Enzymes Roles of...

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