Final answer:
The reaction will NOT speed up without limit as temperature increases since very high temperatures can denature enzymes, reducing or stopping the reaction.
Step-by-step explanation:
The statement that is NOT true for enzyme-catalyzed reactions is: D) the reaction will speed up without limit as the temperature increases. While it is true that reactions can speed up with an increase in substrate or enzyme concentration and may slow down at very low temperatures, the rate does not increase indefinitely with temperature. There is an optimal temperature range for enzyme activity beyond which the enzyme can become denatured, causing the reaction rate to decrease.
In enzyme-catalyzed reactions, both substrate and enzyme concentrations impact the rate of reaction. Initially, an increase in substrate concentration results in a higher reaction rate but this increase plateaus when the enzyme becomes saturated. Similarly, increasing enzyme concentration results in a faster reaction rate when substrate is in excess. Low temperatures can slow down reactions due to decreased molecular movement, but very high temperatures can denature enzymes and slow or halt the reaction totally.