BYS201_SG_Module_I__II_III -...

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Module I - The Chemistry of Life Biology is the study of life 30 million types of organisms Organisms use similar building blocks Living systems have a hierarchy (non-living) Atoms       molecules       cells (living)  multicellular organisms  Atomic composition of living organisms 6 major elements –  Oxygen, Carbon, Hydrogen, Nitrogen, Phosphorous,  Sulfur   Basis of chemical activity: electrons Octet rule: Chemical bonds in biological molecules: Covalent : Sharing electrons (polar and non-polar) Physical strength of covalent bonds: Functional groups in biological molecules:  hydroxyl carbonyl Keto (carboryyl) 1
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carboxyl Amino phosphate sulfhydryl Why are we carbon-based life forms? Ionic : Transfer of electrons from one atom to the other Oxygen radicals and aging Hydrogen bonds : Water : Properties van der Waals forces : Weak electrostatic interactions.    Lipids in water,  graphite, talk Acids and Bases Buffers PH Small shifts in cellular pH play a major role in regulation of biological  activity Chemical Reactions: Chemical reaction occurs when atoms combine or change binding  partners C 3 H 8  + 5O 2    3CO 2  + 4H 2 O 2
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Energetics of Chemical Reactions: Bioenergetics - study of the various types of energy transformations that  occur in living organisms Cells require energy to survive What is Energy? Potential energy Kinetic energy Chemical and physical laws govern the biological reactions Laws of thermodynamics and concept of energy: First law of thermodynamics : Energy can be neither created nor destroyed   Energy can be transduced or transformed System - open and closed Surroundings  E and  E   E = Q-W Exothermic and endothermic reactions Since  E for a particular reaction can be positive or negative, it gives  us no information as to the likelihood that a given event will occur Second law of thermodynamics 3
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Energy cannot be 100% converted.   Every event accompanied by  increase in entropy of universe Entropy (S) Relationship of entropy of a system  vs  its surroundings How can a (Biological) system maintain low entropy? Free Energy (G): H=  G + T S H = Enthalpy (total energy content of the system ~ E)     G=  H - T S T= Absolute temp. S= change in entropy  Value for    G indicates the direction of a reaction Exergonic Endergonic Reversible reactions : How do cells do + G reactions? 1. High reactant:product ratio Dihydroxyacetone phosphate conversion to glyceraldehyde-3-phosphate,  G 0 ' = +1.8 kcal/mole K eq  -> keeps  G “-” 2. Coupled reactions and Standard free energy change  Glutamic acid  + NH 3  <—> glutamine;  G 0’  = +3.4 kcal/mole 4
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