Enzymes

• What are enzymes 


  Biological catalyst that can speed up a reaction without being used

  globular proteins

  have active site where substrate binds

  control metabolic pathways by catalysing them
• how do enzymes work

  have specific active site where only a specific substrate can bind with enough activation energy to form a enzyme substrate complex
• what causes enzymes specific active site

  due to complex tertiary structure and bonds formed
• what’s a catabolic reaction

  when enzymes break down complex molecules into simpler products
• what is anabolic reaction 


  when a more complex molecule is built from two or more simpler molecules
• what is lock and key theory 


  that an enzymes active site is a exact match to a specific substrate and that why enzyme substrate complexes are formed
• what is induced fit theory

  that a enzyme active site is roughly the same shape as substrate and moulds around substrate for a exact fit leading to ideal binding arrangements and maximising ability of enzyme to catalyse reaction. change in shape is conformational change
• how does low temperature affect enzymes

  Enzymes have a specific optimum temp to catalyse reactions at maximum rate

  low temp: reduces rate as substrate and enzymes have lower kinetic energy so move slower and less molecules with activation energy so less frequent successful collisions , less enzyme substrate complexes formed
• how does high temp affect enzymes

  higher temps can increase rate as molecules have more kinetic energy so move faster and more molecules with sufficient activation energy. this means more frequent successful collisions and more enzyme substrate complexes formed
• how does high temp denature enzymes

  high temp starts to break bonds holding enzymes precise shape(hydrogen bonds between amino acids ) . this causes tertiary structure to change and permanently damages active site so substrate no longer complimentary . no more enzyme substrate complexes are formed
• How does ph denature enzymes

  All enzymes have a optimum ph

  changes in ph can denature enzymes as excess of H+ and OH- ions interfere with hydrogen bonds in tertiary structure and change shape of active site so substrate can not fit and no enzyme substrate complexes formed
• Equation for calculating ph

  pH=-log10(H+)
• how does enzyme concentration affect rate

  higher concentration, greater active sites available so more likelihood of enzyme substrate complexes forming as collisions more likely. increased rate until all substrates are used and substrate limiting factor . can be overcome by adding more substrates
• how does substrate concentration affect enzymes

  higher substrate concentration , rate increases as more frequent successful collisions with active site more enzymes substrate complexes form . rate increases until all active sites saturated and enzymes become limiting factors
• what is a competitive inhibitor

  Have similar shape to substrate so can bind to active site of enzymes stopping enzyme substrate complexes from forming and reducing rate . Can be overcome by increasing substrate concentration so substrate more likely to collide with active site than inhibitor
• what is a non competitive inhibitor

  binds to enzymes allosteric sites which alters rate of active site preventing enzyme from binding to it reducing rate . can not be overcome by increasing substrate concentration as active site permanently changes
• how can inhibitors be used in regulating metabolic pathways

  non competitive inhibitors can be used

  as substrate binds to active site process slows down and non competitive inhibitor binds and prevents further reactions from occurring .product can detach and be used else where and inhibitor detaches and allows active site to reshape and process repeats