Enzymes speed up metabolic reactions by lowering energy barriers z Enzyme speed reactions by lowering EA. – The transition state can be reached at moderate temperatures. z Enzymes do not change delta G. – It speed-up reactions that would occur eventually. z Because enzymes are so selective, they determine which chemical processes will occur at any timeEnzymes speed up metabolic reactions by lowering energy barriers z Enzyme speed reactions by lowering EA. – The transition state can be reached at moderate temperatures. z Enzymes do not change delta G. – It speed-up reactions that would occur eventually. z Because enzymes are so selective, they determine which chemical processes will occur at any time