Lecture 2 - Lecture 2 Bioenergetics (Thermodynamics) Why do...

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Lecture 2 Bioenergetics (Thermodynamics) Why do cells require energy? Cellular level Molecular level Move Ion transport; reversible bond formation Grow Synthesis/polymerization Homeostasis (e.g., 37oC, 30 mmHg) Heat production/entropy reduction Molecular level effects imply that cells follow the rules of chemistry, viz. 4 laws of thermodynamics 0) All systems move toward equilibrium (“closed” systems) 1) Energy of a closed system is conserved; also, heat is energy; work is energy [1 calorie = 1 g H 2 O raised from 14.5 o C to 15.5 o C; 1 Joule = 1 kg accelerated 1 m/s 2 x 1 m; 1 calorie = 4.18 J; R (gas constant) =~ 2 cal/mol- o K = 8.31 J/ mol- o K] 2) Entropy of a closed system increases 3) You can’t get to absolute zero (at absolute zero, S = 0) Other formulations of 2nd law: Heat flows spontaneously from hot to cold bodies. Systems spontaneously seek highest dispersion of energy. Disorder increases. Second law poses a problem: How can cells reproduce—make more cells from disordered raw materials? Cells are not a closed system. They produce order through a coupled disorder of the environment. Δ
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Lecture 2 - Lecture 2 Bioenergetics (Thermodynamics) Why do...

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