Question

enzyme activity
source: adapted from
http://imgmascience.files.wordpress.
com/2011/11/enzyme - rate - of - reaction1.jpg
the most likely reason the action of the enzyme decreases after 40°c is that

1. the dna in the enzyme mutates and can no longer break down the starch

2 enzymes die after working for a long period of constant activity in the body
3 the shape of the enzyme changes due to environmental conditions
4 as the temperature of the enzyme rises, the ph of the environment changes, deactivating the enzyme

Explanation:

Enzymes are proteins, and their activity is highly dependent on their three - dimensional shape. High temperatures (above the optimal temperature, which is around \(40^{\circ}C\) in this case) can cause the enzyme's shape to change (denaturation). DNA is not part of most enzymes (except ribozymes, which are RNA - based and not relevant here). Enzymes are not living organisms and do not "die." Also, the graph only shows the effect of temperature, not pH.

Answer:

1. the shape of the enzyme changes due to environmental conditions