The rate of an enzyme -catalyzed reaction is measured at several temperatures, g
ID: 495026 • Letter: T
Question
The rate of an enzyme -catalyzed reaction is measured at several temperatures, generating the curve shown below. Explain why the enzyme activity increases with temperature and then drops off sharply. Please see figure 3 Using what you know about the structures of the amino acid side chain .Choose an amino acid side chain to play the following roles in an enzymatic mechanism: Participate in proton transfer Act as a nucleophile Which of the following is the most effective way to increase the rate of a biochemical reaction? increase the temperature increase the concentrations of the reactants increase or decrease the pHExplanation / Answer
Answer for question 8:
Usually any chemical reaction is promoted by increase in reaction temperature. This is due to the fact of lowering the transition energy required for forward reaction to occur. Depending on kind of reaction many times a few degrees (Celsius) raise is enough to increase the rate of reaction. It’s commonly accepted that rate of reaction doubles for every 10oC rise in temperature.
For reactions catalysed by enzymes also increase in temperature increases the rate of reaction due to the fact of lowering the transition energy. Few degrees (1 or 2) raise in temperature usually increases the rate by 10 or 20%. This is true for many reactions happening at ambient temperature. However the enzymes lose their shape and structure (denatured) at higher temperatures which results in sudden drop in rate of reaction beyond a temperature limit, usually higher than 40o C. This can be clearly seen in a graph when a rate of reaction drawn against different temperatures.
Answer for question 9:
Amino acids with carboxylic acids in their side chain participate in proton transfer in an enzymatic reaction. Ex. Aspartic acid
Amino acids with amino groups in their side chain act as nucleophiles in a reaction. Ex. Arginine
Answer for question 10:
Increasing the concentration of reactants is most effective way as it makes available more
substrate for the enzyme.
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