The Effect of substrate Concentration
As the concentration of substrate increases, the rate of reaction also increases until the point saturation occurs. It means as you increase the concentration, rate keeps increasing and then one point comes when the maximum rate is achieved and there is no free enzyme to bind with substrate and all the active sites of enzyme are bound to the substrate. So after that point, increasing the concentration wont have any effect. What is the maximum for each enzyme is usually given by Km value (michealis menten graph or the other one called sumting like Lineweaver burke plot). The Km value is the rate constant or it can be explained as how much substrate concentration is required by an enzyme to reach to the half of maximum rate or velocity of enzyme. Each enzyme has different Km values. So I hope that answers ur quesiton- wherever the Vmax occurs and it intersects the curve drawn for substrate concentraion and velocity (or rate of reaction), that point is the saturation point or maximum substrate concentration to have maximum rate of the reaction.
Based on our experiment, we got negative value for rate of hydrolysis (V). According to the theory we are not supposed to get negative value for (V). In other words it states that, when the substrate concentration change and while enzyme concentration is keeps constant, the rate of reaction will increase. This is because there are a few error that occurred during we ran the experiment.
The Effect of Temperature
Based on the plotted graph, the line for 10°C has the Km value of 0.30. The line for 28°C has the Km value of 0.14. The line for 35°C has Km value of 0.07 while the Km value for 40°C is 0.10. The lower the Km value, the higher the affinity to the substrate. As a result, the rate of reaction is greater. According to the three different temperatures applied, temperature of 35°C is the optimum temperature for the enzyme to react as its Km value is the lowest among all. On the other hand, the lines share the same Vmax value, which is 0.003. Although temperatures change, the active site does not change. The substrates can still bind with the enzyme. The only difference is the rate of reaction. The amylase reacts the best at temperature of 35°C.
The Effect of pH
pH can give several effect on structure and activity of an enzyme. For example, pH can have an effect of the state of ionization of acidic or basic amino acids. Acidic amino acids have carboxyl functional groups in their side chains. Basic amino acids have amine functional groups in their side chains. If the state of ionization of amino acids in a protein is altered then the ionic bonds that help to determine the 3-D shape of the protein can be altered. This can lead to altered protein recognition or an enzyme might become inactive.
Changes in pH may not only affect the shape of an enzyme but it may also change the shape or charge properties of the substrate so that either the substrate cannot bind to the active site or it cannot undergo catalysis.
The most favorable pH value - the point where the enzyme is most active - is known as the optimum pH.