chap 4.2 enzymes

• enzymes are highly specific in action.
• lock and key hypothesis

  the substances that the enzymes act on are substrates.
• enzymes have active sites which is the place on the surface on the enzyme molecule where the substrate with a matching shape can fit.
• substrate is the key and the enzyme is the lock.
• when substrate binds to the active site of enzyme, an enzyme-substrate complex is formed. it is a temporary molecules formed when substances bind to the enzyme. reactions take place at the active site to convert the substrate molecules into product molecules. the enzyme remains chemically unchanged for more reaction in the future.
• Lock & key hypothesis

  An enzyme has a specific three dimensional shape and has a depression called the active site, the substance on which the enzyme acts is called the substrate
• lock and key hypothesis

  • Only the substrate with a complementary shape to the enzyme can fit into the active site of the enzyme
  • The enzyme is the lock and the substrate is the key
• lock and key hypothesis

  1. While the substrate is attached to the active site, a chemical reaction occurs

  2. The substrate is converted to the products

  3. After the reaction, the products will leave the active site and they enzyme will remain chemically unchanged so that another reaction can occur
• enzymes speed up chemical reactions

  they lower the activation energy needed to start the reaction
• enzymes are specific in action,

  only substrates that have a complementary shape to the active site can fit into the enzyme. when substrate binds to active site of enzyme, it forms a enzyme-substrate complex.
• enzymes are required in minute amounts and remain chemically unchanged at the end of reactions.

  enzymes are efficient molecules. Since they remain chemically unchanged after a reaction they can be used over and over again so a small amount of enzyme is needed to catalyse a large amount of substrate.
• enzymes are affected by temperature.

  enzymes is less active at lower temps. at low temps kinetic energy is low so the enzyme and substrate move slowly so the rate of collision is low
• as the temperature increases, the rate of enzyme reaction increases, as the kinetic energy is higher , collision is higher so this increases the rate of enzyme-substrate complex formation. This is the optimum temperature of the enzyme.
• collision is the rate of substrate molecules colliding and fitting into the active site of the enzye
• denaturation is the change in the three dimensional structure of an enzyme caused by heat or chemicals.
• increasing the temperature above the optimum causes a rapid decrease in the rate of enzyme reaction, the active site of the enzyme begins to lose its original shape and is no longer complementary to the shape of the substrate molecules.
• when the temperature is above he optimum temperature of the enzyme, all the enzyme molecules have been denatured.
• denaturation results in the loss or alteration of the enzymes active site. so substrate can no longer fit into the enzymes active site so no reaction can occur. once a enzyme is denatured, it can no longer act as a catalyst
• enzymes are affected by pH