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Factors Affecting Enzyme Action - Coggle Diagram
Factors Affecting Enzyme Action
Effect of Enzyme Concentration on the Rate of Reaction
Since there are too few enzymes, not all substrates have an active site. Therefore, there are fewer E-S complexes being formed.
The rate of the reaction increases as there are more active sites available. This means that more substrates can occupy more active sites and more E-S complexes can be formed.
Since there are more enzymes than substrates and all substrates have already been occupied with an active site, the maximum E-S complexes have been formed. Adding more enzymes will not change the rate of the reaction.
Measuring Enzyme-Catalysed Reactions
For enzymes to work, it must come into physical contact with the substrate, to form an enzyme-substrate complex, and have an active site that can be induced to fit into the substrate.
When measuring enzyme-catalysed reactions, two events that are most frequently measured are the disappearance of the substrate and the formation of the products of the reaction.
The initial rate is high as there are lots of substrate molecules so there is a high chance of collisions, which means that there are many E-S complexes forming.
All enzyme active sites are occupied and an increased amount of products are created.
As the reaction proceeds, there are less substrates available. There is a lower chance that the substrate will collide with the active site, therefore there are fewer E-S complexes forming, as the products "may get into the way").
The rate of the reaction therefore slows.
The graph fattens out because all the substrates have been used up and no new products can be formed.
Effect of Temperature on Enzyme Action
An increase in temperature increases the rate of reaction because there is more kinetic energy so there are more frequent successful collisions which leads to more E-S complexes, increasing the rate of reaction.
When the temperature surpasses the optimum temperature, the hydrogen, ionic and disulphide bonds in the tertiary structure break.
Therefore, the shape of the active site changes and the active site is less specific to the substrate.
So fewer E-S complexes form so the rate decreases and the enzyme eventually denatures.
Effect of pH on Enzyme Action
Different enzymes have different optimum pH. The tertiary structure bonds are affected by H⁺ and OH⁻ ions.
The optimum pH shape of the active site is the most complementary to the shape of their substrate as more E-S complexes are formed, therefore the rate of the reaction is at an optimum.
Changing the pH decreases the rate of the reaction.
Changing the pH changes the charges of amino acids in the active site, therefore the substrate cannot bind as easily and cannot form bonds with the active site. Therefore, the shape of the active site changes so there are fewer E-S complexes, which slows the rate of the reaction.
The hydrogen and ionic bonds being broken by the H⁺ and OH⁻ ions, changes the tertiary structure, which changes the shape of the active site. Fewer E-S complexes are formed which slows the rate of the reaction.
Small changes in pH do not cause a permanent change to the enzyme as the bonds can be reformed.
Extreme changes in pH causes the enzymes to denature and permanently lose function.
Effect of Substrate Concentration on the Rate of Enzyme Action
Since there are too few substrates, not all active sites have been occupied. Therefore, there are fewer E-S complexes being formed and the rate of the reaction has not reached its maximum possible yet.
Since there are more substrates available (twice as many than before), all the active sites are now occupied and the maximum number of E-S complexes have been formed. Therefore, the rate of the reaction has increased (doubled) to its maximum.
An addition of further substrates has no effect on the rate of the reaction as there are no more active sites avaiable.