Biology 2.1.4- Enzymes

• Explain the stages of the lock and key model

  The enzyme molecule and substrate molecule have a perfect complimentary fit

  This creates the enzyme substrate complex, and when the substrate splits, the enzyme product complex

  Products are produced

  
• Explain the stages of the induced fit model

  The enzyme molecule and substrate molecule have a near complimentary fit

  The enzyme molecule changes shape slightly to mould around the substrate, putting pressure on it, meaning its easier to break bonds. This is the enzyme substrate complex

  The substrate splits forming the enzyme product complex and producing products

  
• Describe the effect of increasing temperature on enzymes up to optimum temperature

  Increasing temperature means increasing kinetic energy of enzyme molecules and substrate molecules

  The frequency of successful collisions increases, meaning number of enzyme substrate complexes increases

  
• Describe optimum temperature for enzymes

  Highest frequency of successful collisions and number of enzyme substrate complexes

  
• Describe the effect of increasing temperature on enzymes, past optimum temperature

  Hydrogen bonds vibrate, which breaks bonds and partially denatures the active site of enzyme molecules

  The substrate is no longer a complimentary fit

  When fully denatured, there is zero successful collisions

  
• Describe the effect of increasing enzyme molecule concentration on rate of reaction

  At the start, enzyme molecule concentration is the limiting factor

  After a point, further increase in number of enzyme molecules sees no change in rate of reaction

  
• Describe the effect of increasing substrate molecule concentration on rate of reaction

  At the start, substrate molecule concentration is the limiting factor

  After point, any further increasse in number of substrate molecules sees no change in rate of reaction

  
• What is the Vmax

  The fastest possible initial rate of reaction
• Describe competitive inhibition

  The inhibitor molecule has a similar shape and can bind to the active site of the enzyme molecule, meaning other substrate molecules can't bind
• Describe non-competitive inhibition

  Non-competitive inhibitor binds to the allosteric site of the enzyme molecule which leads to a change in the tertiary structure and therefore a change in shape of the active site

  This means substrate molecules can no longer bind
• Describe end-product inhibition

  The final product of the reaction inhibits the activity of the first enzyme molecule

  This maintains an optimum level of a multistep reaction
• Effect of increasing pH on initial rate of reaction

  As pH increases initial rate of reaction increases until the optimum pH

  At the optimum there is, the highest frequency of successful collisions and highest number of enzyme-substrate complexes
• What happens when the pH is increased or decreased from the optimum pH

  Ionic bonds are broken by ions in the solution (H+ or OH-)

  The higher the concentration, the more they interfere with the tertiary structure and the more the active site denatures

  The active site is no longer complimentary to the shape of substrate molecules
• Explain the temperature coefficient

  For every 10 degree increase in temperature, the initial rate of reaction doubles

  Q10 = R2/R1
• What is a cofactor

  A substance that has to be present to ensure than an enzyme-catalysed reaction takes place at the apropriate rate
• What is a coenzyme

  Small organic non-protein molecule that binds temporarily to the enzyme's active site

  Coenzyme is chemically changed and needs to be recycled
• What are extracellular enzymes

  Enzymes made within a cell and released outside of it
• What are intracellular enzymes

  Enzymes made within a cell and used within cells