Enzymes and Thermodynamics I MSc I Sem PDF

Enzymes and Thermodynamics LS101 H= Enthalpy G= Gibbs free energy T= Temperature S= Entropy  Basic definitions Anabolic reactions Anabolic reactions are those where simple molecules are liked to form complex molecules. They require the input of energy and capture it in the...

Enzymes and Thermodynamics LS101 H= Enthalpy G= Gibbs free energy T= Temperature S= Entropy  Basic definitions Anabolic reactions Anabolic reactions are those where simple molecules are liked to form complex molecules. They require the input of energy and capture it in the chemical bonds formed Eg: Synthesis of proteins from amino acids Catabolic reactions They involve the breakdown of complex molecules to simpler ones Energy stored in chemical bonds are released Eg: Polysaccharide starch being hydrolysed to simpler molecules. Anabolic and catabolic reactions are often linked. The energy released by catabolic reactions are used to drive anabolic reactions.  Basic definitions (contd.) Enthalpy (H) - thermodynamic quantity equivalent to the total heat content of a system. It is equal to the internal energy of the system plus the product of pressure and volume. Entropy (S) - thermodynamic quantity representing the unavailability of a system's thermal energy for conversion into mechanical work, often interpreted as the degree of disorder or randomness in the system. Exergonic reaction – Energy is released, reactants form lower energy products. Endergonic reaction – Energy must be added for the reaction to take place, reactants form higher energy products. Fig. Coupling of ATP Hydrolysis to an Endergonic Reaction  Bioluminescence The production of light by living organisms is referred to as bioluminescence. It is an endergonic reaction driven by ATP hydrolysis that involves the interconversion of energy forms (chemical to light). This reaction occurs in a variety of organisms including those in marine habitats, worms, mushrooms and microorganisms. The light produced is generally used to avoid predators or as a mating call. Note: Bioluminescence of firefly is a result of endergonic reaction giving luminescence by luciferin (an organic substance which on oxidation by the enzyme luciferase generates light), this is coupled to the exergonic ATP (Adenosine triphosphate) release. DIPF= Diisopropylfluorophosphate Exercise Identify enzyme name (allosteric regulation Rate-limiting Enzyme)  Definitions Allosteric enzymes are enzymes that have an additional binding site for effector molecules other than the active site. The binding brings about conformational changes, thereby changing its catalytic properties. The effector molecule can be an inhibitor or activator. Non-allosteric enzymes are the enzymes that do not process allosteric sites other than the active site. Therefore, they are simple enzymes that have only one enzyme active site. These enzymes are substrate-specif ic enzymes. They are also non- regulatory enzymes. Their reactions show a hyperbolic curve. Biosynthesis of catecholamines pathway and enzymatic steps Norepinephrine Epinephrine Co-factor --- Oxidoreduction  List of co-factors related to enzyme kinetics NAD, NADH, FAD, FADH, NADP, NADPH Cofactor related to ions: SAM (s-adenosyl methionine) Cu2+, Mg2+, Ca2+, Fe2+ Cofactor found in air: O2, Cofactor related to vitamins: ascorbate