Enzymes

• what are enzymes? globular proteins that have a tertiary structure
• what is an active site? active site has a specific shape which requires a specific substrate that can fit an bind
• what is the active site shape determined by? the sequence of amino acids in the polypeptide
• what is the lock and key hypothesis? the active site is a fixed shape - substrate is a specific shape and binds to the active site producing an enzyme-substrate complex - substrate molecules are either digested or combined to form new products - enzyme is not affected by the reaction and can be reused
• what is anabolism? two substrate molecules combined to form a single product molecule
• what is catabolism? many enzymes are involved in breaking down a complex substrate molecule into two or more product molecules
• what is the induced fit hypothesis? - substrate binds to the active site and the shape of active site slightly changes and stronger bonds are formed - enzyme-substrate complex is formed - weakens bonds in the substrate which lowers activation energy - products are released from substrate and active site returns to original shape - enzyme can be reused
• what is the effect of pH on enzymes? - changes in pH can cause bonding between amino acids to change therefore cause changes to secondary and tertiary structure of a protein - change in pH can cause a change in charge
• how does change in charge affect an enzyme? - changes ability of the enzyme's active site to form bonds with a substrate - if bonds cant form, activation energy cant be lowered
• how does temperature affect enzymes? enzymes and substrates have more kinetic energy up to optimum temperature so there are more successful collisions and more enzyme-substrate complexes formed and rate of reaction increases
• what happens to enzymes above optimum temperature? - bonds in the enzyme begin to vibrate and eventually break - loss of secondary and tertiary structure and the shape of active site changes - enzyme is fully denatured
• for rate of reaction on a graph how do you calculate rate? change in y axis value / change in x value
• Describe A A: - as temp increases, molecules gain kinetic energy - increased frequency of successful collisions - increased frequency of enzyme-substrate complexes formed - rate of reaction increases
• Describe B B: - at optimum temp, maximum number of enzyme-substrate complexes are forming at the same time - rate reaches a maximum - products will be produced the fastest at this point
• Describe C C: - temperatures above optimum, increased kinetic energy causes bonds to break - active sites change shape - less enzyme-substrate complexes formed - enzymes begin to denature and reaction stops
• Describe A - at optimum pH, shape of active site enables bonds to form successfully - greatest frequency of enzyme-substrate complexes formed here - highest rate of reaction
• Describe B - low pH, high conc of H+ ions - more amino groups will have a positive charge so affects hydrogen and ionic bonding - changes 3D shape of the active site - as pH becomes more acidic fewer bonds can form between active site and substrate - fewer enzyme-substrate complexes formed
• Describe C - pH values above optimum, not enough H+ ions present - 3D shape of active site changes making it less able to form bonds with the substrate - fewer bonds can form between active site and substrate - fewer enzyme-substrate complexes formed - rate of reaction decreases
• what is competitive inhibition? - an inhibitor of similar shape binds temporarily to the active site - active site is blocked for the normal substrate so it cannot bind to the active site and fewer enzyme-substrate complexes are made - rate of reaction decreases
• what is non-competitive inhibition? - the inhibitor binds to the allosteric site of an enzyme - changes the 3D shape of the active site - fewer enzyme-substrate complexesare made and rate of reaction decreases