Enzymes

• What is an enzyme?

  A biological catalyst Made from polypeptide chains its tertiary structure allows it to form a globular protein.
• what is the Job of an enzyme

  they are specific to one substrate and allow reactions to occur rapidly at ordinary temps by lowering the activation energy . They can be intracellular or extracellular.
• Structure of an enzyme

  large proteins with a complicated 3D space with an active site; biological catalyst that speeds up chemical reactions but is never consumed by it . Substrate has a complementary shape to the active site
• Active site

  An active site is a specific region on an enzyme that is functional. It's made up of few amino acids and is where the substrate bind to the enzyme. it is the tertiary structure which determines the shape of an active site and how the substrate is broken down.
• substrate

  the molecule on which an enzyme acts. It will be complementary to the active site and once bonded forms an enzyme substrate complex
• activation energy

  Energy needed to get a reaction started

  
• Lock and key model


  The model of the enzyme that shows the substrate fitting perfectly into the active site

  
• induced fit hypothesis

  active sites change shape to accommodate the shape of specific reactants. It returns to its original shape once the reaction is complete

  
• what affects the rate at which enzymes work?

  - concentration of enzyme

  - concentration of substrate

  - pH ( too acidic/alkaline)

  - temperature
• how does an increase in temperature effect rate of reaction

  A rise in temp increases kinetic energy so more collisions of substrate and enzymes take place per second forming more enzyme substrate complexes. At some point though (around 60 degrees) an enzyme becomes denatured changing the enzymes shape so it can no longer function.

  
• How does pH effect rate of reaction

  every enzymes has a pH at which they work best we call this the optimum temperature. if the pH increases or decreases slightly they won't work as well as it alters the charges on an amino acid that make up the active site of the enzyme.. therefore the substrate can no longer bind to the active site.

  
• How does enzyme concentration affect enzyme activity?

  usually will increase rate of reaction as substrate can be broken down quicker as there are more enzymes for it to collide with. as there are more enzymes more collision per second occur. however is the substrate is limited the rate of reaction will eventually level out.

  
• How does substrate concentration affect enzyme activity

  rate of reaction will increase proportionally for a while as more enzyme substrate complexes form due to more collisions per second. however since enzymes are limited rate of reaction will eventually level out as they can only break down so many at one time.

  
• Enzyme inhibitors

  substances that directly and indirectly interfere with the functioning of the active site of an enzyme reducing its activity.
• competitive inhibitors

  A substance that reduces the activity of an enzyme by entering the active site in place of the substrate whose structure it mimics.this reaction is sometimes reversible.

  
• non-competitive inhibitors

  bind to another part of an enzyme (allosteric site), causing the enzyme to change shape and making the active site less effective. this reaction is often irreversible