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3.1- enzymes : globular proteins - Coggle Diagram
3.1- enzymes : globular proteins
enzyme structure
Globular protein with a specific 3D shape/ tertiary structure depending on the amino acid sequence of the primary protein structure
The functional region of the enzyme is the active site, consisting of a few catalytic amino acids
the structure of active site is complementary to substrate (s) which binds to the active site and forms an enzyme-substrate complex
The tertiary structure of the enzyme determines its function as it determines the shape and properties of the active site. --If the tertiary structure is altered the shape of the active site will change and no longer be complementary to its substrate so e-s complexes will not be able to form
enzyme function
Induced fit Model
misconception of lock/key model
active site has a fixed complementary shape that will only fit the complementary substrate
the active site is a general shape that undergoes a conformational change when interacting when a specific substrate which which causes the change in shape.
enzyme binds to the active site and an e-s complex forms. The active site undergoes a conformational change in order to be complementary to the substrate molecule and the change in shape of the active site can put strain on bonds causing them to break
enzymes are proteins functioning as biological catalysts that lower the activation energy of reactions (often allow reaction to take place at a lower temp (37C body temp) than it could without the enzyme by lowering the level of thermal energy necessary for reaction)---> therefore increasing the rate of metabolic reactions
why does formation of an enzyme-substrate complex reduce the activation energy/increase rate of reaction?
two substrate molecules that are joined; the induced fit causes the shape of the active site to change, the e-s complex forces stress on bonds, causing them to break/form and reduces repulsion between molecules so they can bond more easily
catalysing the breakdown (hydrolysis) of molecules- induced fit and change in shape of active site puts strain on bonds in substrate molecule causing them to break more easily
competitive inhibitor
increasing the concentration of inhibitors will lower enzyme activity : molecules with similar shape to the substrate compete with substrate molecules to bind with the active site of its enzyme.
Increasing the inhibitor concentration can cause the active sites to become saturated
eventually the, all the substrate molecules will be able to occupy an active site as competitive inhibitors are not permanently bound to the active sites. How fast this happens is controlled by the concentration of inhibitor
Increasing the substrate will increase the rate of reaction as the substrates chance of colliding successfully with the enzyme and binding to the active site increases
non-competitive inhibitor
Inhibitor molecule binds to the allosteric site on the enzyme separate to the active site which causes the shape of the enzyme to change so that substrate molecules can no longer bind with it. This process is usually non-reversible so the enzymes can no longer function
Increasing the substrate concentration does not help to decrease the effect of the inhibitor since the inhibitor molecules are not competing with the substrate for the active site.
since the process is usually non-reversible , the same rate of reaction will not be achieved as substrate concentration increases
increasing the substrate conc., the rate of reaction is not only a lot slower but the rate of reaction reaches a constant far below the rate for when an inhibitor is not present
End product Inhibition: the final product of a sequence of enzymes is an exceptional non-competitive inhibitor as it is reversible
the end product binds to an allosteric site on an enzyme temporarily inactivating it to decrease or limit the rate of product formation in order to tightly regulate the essential levels of product
Differences of competitive and non-competitive inhibitors
non-competitive inhibitors: do not have a similar structure to the substrate, bind to a site away from the active site, non-reversible process as it usually alters the tertiary structure and shape of active site permanently so the enzyme can no longer form e-s complexes
competitive inhibitors: similar structure to substrate, bind to active site, reversible process
Effect of substrate concentration on rate of reaction
Increasing the substrate available increases the RoR as more substrate available means more frequent successful collisions and more e-s complexes form. until the saturation point at which the number of enzymes limits the reaction and all active sites are occupied so adding more substrate has no effect
Effect of temperature on rate of enzyme controlled reaction: enzymes have optimum temps
extreme temperatures lower enzyme activity
at a very high temp, bonds can be broken in the structure of the enzyme causing the tertiary structure to be altered which causes the shape of the active site to change and means that it can no longer fit the substrate as it has denatured. Denaturing means that less e-s complexes form
at a very low temp, the particles have a low KE so move around much slower and enzymes and substrates collide less frequently and if so collide with a lower amount of energy so less frequent successful collisions so less e-s complexes form
Effect of enzyme concentration on rate of reaction
Increasing the amount of enzymes means that collisions between enzymes and substrates are more frequent and more successful collisions happen in the same amount of time so more e-s complexes form in a given time and RoR increases as more active sites are available
if the graph reaches a constant RoR, the amount of substrate limits the RoR so adding more enzymes has no further effect once there is enough enzymes to bind with all the substrates
Effect of pH on enzyme controlled reaction: enzymes have optimum pHs
at extreme pHs, above and below the optimum pH: H+ or OH- ions in solution can begin to disrupt bonds that contribute to the tertiary structure causing the structure and shape of the active site to change so it no longer fits its substrate as it denatured. less e-s complexes form