3.1.4.2 Enzymes Flashcards
What are enzymes?
biological catalysts that speed up the rate of reaction by lowering the activation energy
What protein structure do enzymes have?
tertiary structure - golbular protein
What is an active site?
small depression in larger enzyme molecule made up of a small number of amino acids
How does the induced fit model work?
intermolecular forces between active site and substrate cause active site to change shape slightly to be complementary to the substrate
How does the induced fit model lower activation energy?
strains bonds in the substrate, so less energy required to break the bonds
What is it called when the active site changes shape?
conformational change
Why does increasing temp increase rate of reaction?
-increasing KE of enzyme
-more successful enzyme-substrate collisions
Why does rate decrease past the optimum temperature?
-enzyme denatures
-Hydrogen bonds in tertiary structure are disrupted, so structure deforms
-active site changes shape, NO LONGER COMPLEMENTARY
Why does rate of reaction decrease as pH changes from optimum?
-ionic forces and hydrogen bonds are disrupted (tertiary structure deforms)
-alters charge on amino acids that make up the active site
-active site NO LONGER COMPLEMENTARY, so substrate cannot bind
What is the maximum rate of reaction called?
V max
How does a competitive inhibitor reduce the rate of reaction?
-binds to active site of enzyme (similar shaper to substrate)
-so reduces the number of enzyme-substrate complexes that can be formed, by ‘blocking’ the active site
How does a non-competitive inhibitor reduce the rate of reaction?
-binds to allosteric site
-which can permanently change the shape of the active site, meaning no more substrates can bind to the active site as it is NO LONGER COMPLEMENTARY
Why can’t a non-competitive inhibitor bind to the active site of an enzyme?
has a different shape to substrate - not complementary
Will changing the substrate conc. change the effect of competitive inhibitors?
yes - increases chance of enzyme-substrate collisions
Will changing the substrate conc. change the effect of non-competitive inhibitors?
no - as if active site has changed shape, substrate can no longer bind as it is NO LONGER COMPLEMENTARY
What is a metabolic pathway?
series of reactions in which each step is catalysed by an enzyme
What are the characteristics of a metabolic pathway?
-highly structured
-maintains a steady conc. of a particular chemical in a cell (can often act as an inhibitor of the enzyme at the start of the reaction)
What is a coenzyme?
a non-protein that binds to the active site to make it complementary to the substrate
