Enzymes and Catalysis

• E subscript A


  Activation energy abbreviation
• Activation energy


  Initial energy input that has to go into a reaction that gets paid back as the reaction proceeds
• Transition state


  In order to get chemical reactions, bonds have to break, and when they break they have to get into a highly unstable, high-energy state that is spurred by the activation energy and doesn't last long due to its instability
• Gibbs free energy (G) of a system is a measure of usable energy of a system
• Delta G


  Change in free energy of a system as it goes from an initial state (reactants) to a final state (products) and its sign (+-) says if it'll happen spontaneously or not
• Exergonic reaction


  Reaction that happens spontaneously with negative deltaG free release where the products have more energy than the reactants
• Endergonic reaction


  Reaction that requires activation energy (energy input) to happen, has positive deltaG free energy, and results in energy storage (reactants more energetic than products)
• Spontaneous


  When a reaction happens on its own
• Exergonic reaction

  
• Endergonic reaction

  
• The transition state is always at a higher level of energy than the reactants or the products of a reaction (Ea always has a positive value)
• Exergonic reactions require less activation energy than endergonic reactions because there is less of a hill to get over (higher to lower only needs a little push up but lower to higher needs a LOT of energy to get higher than even the final reaction)
• Heat


  The typical source of activation energy, which is absorbed and speeds up molecules so they're more likely to collide
• Required activation energy is closely related to its rate because it's based on randomness, so the odds of the full reaction being able to happen are lower and lower. Some have such small odds they need catalysts to happen, like propane
• Catalysis


  Process of speeding up a chemical reaction by reducing its activation energy
• Catalyst


  In biology, enzymes, which speed up chemical reactions by reducing activation energy without being a reactant itself
• Enzyme


  Biological catalyst that works by binding to molecules and putting them in a position where the chemical bond making/breaking happens more readily
• Enzymes do not change deltaG (amount of free energy being released) they just lower the energy required to enter the transition state
• Substrate


  Reactant molecules that enzymes bind to
• Active site


  Part of the enzyme that binds to a reactint by having specific proteins on it with a very specific shape targeted towards binding to specific molecules
• Warmer temperatures generally increase enzymatic activity, but anything above 40 C and they start to denature (lose efficacy)
• Changes in pH can affect the amino acids at enzyme active sites, potentially making them denature
• Induced fit


  The adjustment of an enzyme to fit snugly in the substrate
• Enzymes work by bringing two molecules together, changing active site environments to be more favorable (more acidic, more nonpolar, etc), some take part in the reactions themselves. They all go back to their original state in the end though