r eigy SIBrage using everyday its. 3. You have been assigned to lead a lab that
ID: 274051 • Letter: R
Question
r eigy SIBrage using everyday its. 3. You have been assigned to lead a lab that takes plant material and converts it into ethanol for fuel. The process relies entirely on enzymes that break down the cellulose into ethanol. How would each of the following factors affect the efficiency of your task: temperature, pH, enzyme concentration, substrate concentration, allosteric inhibitor, competitive inhibitor, allosteric activator? For each factor, explain what would happen if you double it and what would happen if you cut it in half.Explanation / Answer
Ethanol is produced from cellulose called cellulosic ethanol. It is mainly produced from lignocellulose which is the main component of the plants. Ethanol produced in this manner can be used as an alternative fuel.
The major steps involved in conversion of cellulose to ethanol are pretreatment of the biomass to improve accessibility of enzymes, enzymatic hydrolysis of biomass which involves conversion of cellulose into monomer sugar (glucose), and fermentation of sugars into ethanol. Cellulose is broken down into glucose by cellulases. Apart from this, xylanase and hemicellulase enzymes are also able to convert cellulose into fermentable sugars. Similarly, fermentation of sugar is also carried out with the help of various enzymes. Hence, the conversion process relies entirely on enzymes.
Factors that affect the efficiency of enzymes involved in cellulose conversion
Temperature
Effect of temperature on enzyme activity is complex. When there is rise in temperature, not only the rate of reaction increases, inactivation of enzymes due to its denaturation also occurs. Hence, the optimum temperature (Topt) has to be observed. Temperature at which inactivation of enzymes occurs differs for different enzymes. Moreover, if the temperature becomes too low, the activity of the enzymes will be slow which eventually come to a halt.
Hence, if the temperature is doubled, denaturation of enzyme protein occurs and when it is halved, the activity of the enzyme stops.
pH
Enzymes are affected by changes in pH. Extremely low or high pH can lead to complete loss of activity of the enzymes. The point at which the enzyme is most active is called the optimal pH. The optimal pH for invertase (enzyme involved in fermentation) is found to 4.5. Maximal activity for cellulase enzymes is found to be in between 4.2 to 5.8. Small changes in pH above or below optimum pH do not cause a permanent change to the enzyme, but extreme changes can cause denaturation of enzymes.
Hence, if the pH is halved or doubled the enzymes will become inactive.
Enzyme concentration
Increase in enzyme concentration will increase the rate of reaction. This is due to the fact that more enzymes will start colliding with the substrate molecules. But this will have effect only up to a certain concentration after which enzyme concentration will not be a limiting factor.
Hence, on doubling the enzyme concentration, the rate of reaction may tend to increase, while if it is halved, the rate tend to decrease (depending on the optimal concentration).
Substrate concentration
Increase in substrate concentration increases the rate of reaction. This is due to the fact that more substrate molecules will start colliding with enzymes resulting in the formation of more products. But substrate concentration will no longer be a limiting factor after certain concentration. The enzymes become saturated and will work at maximum possible rate.
Hence, on doubling the substrate concentration, the rate of reaction tend to increase, while if it is halved, the rate tend to decrease (depending on the optimal concentration).
Inhibitors alter the catalytic activity of enzymes.
Allosteric inhibitor
It binds to an enzyme at a site other than the active site called the allosteric site. When an allosteric inhibitor binds to an enzyme, all the active sites of the enzyme alters which result in the inactivation of enzymes.
Hence, if the concentration of allosteric inhibitor is doubled, the activity of enzymes decreases resulting in less effective reactions. But if the concentration of allosteric inhibitor is halved, the rate of reactions increases.
Competitive inhibitor
An inhibitor resembling the substrate that binds to the active site of the enzyme blocking the binding of the substrate is called a competitive inhibitor. Hence, it competes with the substrate for the enzyme. The reaction gets slowed when there is an increase in competitive inhibitor concentration.
Therefore, if the concentration of competitive inhibitor is doubled, the activity of enzymes (binding of substrate to it) decreases resulting in less effective reactions. But if the concentration of competitive inhibitor is halved, the rate of reactions increases since there will be lesser amount of it to compete with the substrate. Hence, the enzyme is able to accept the substrate and the reaction occurs effectively.
Allosteric activator
Allosteric activators binds to a location in the enzyme other than the active site resulting in an increase in the active site. Sometimes, the substrate itself serves as an allosteric activator.
Hence, increase in allosteric activator concentration increases the enzymes activity resulting in effective reactions to occur. But if allosteric activator concentration is halved, the reactions tend be less effective.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.