What effect do temperature and pH have on enzyme activity?

What effect do temperature and pH have on enzyme activity?

• A. They have no effect on enzyme activity.
• B. They can denature enzymes at extreme values, reducing activity.
• C. They only affect the substrate, not the enzyme.
• D. They always increase enzyme activity.

Answer: (B)

Enzyme activity depends on the shape and charge of the enzyme, which are set by the protein’s three-dimensional structure and the ionization state of its amino acids. Temperature and pH influence both of these factors. Within a normal, moderate range, higher temperature increases molecular collisions, so the reaction rate goes up. But there is a limit: if the temperature gets too high, the weak bonds that hold the enzyme’s shape break, the protein unfolds, and the active site no longer fits the substrate. That loss of structure markedly lowers or stops activity. Similarly, enzymes have an optimal pH where the charged groups in and around the active site are in the right states to bind substrate effectively. Deviations from this optimum—especially extreme pH values—alter ionization, disrupt bonds, and can destabilize the overall structure, also reducing activity or causing denaturation. So temperature and pH can dramatically affect how well an enzyme works, and extreme values can denature the enzyme, leading to reduced activity.

Enzyme activity depends on the shape and charge of the enzyme, which are set by the protein’s three-dimensional structure and the ionization state of its amino acids. Temperature and pH influence both of these factors. Within a normal, moderate range, higher temperature increases molecular collisions, so the reaction rate goes up. But there is a limit: if the temperature gets too high, the weak bonds that hold the enzyme’s shape break, the protein unfolds, and the active site no longer fits the substrate. That loss of structure markedly lowers or stops activity.

Similarly, enzymes have an optimal pH where the charged groups in and around the active site are in the right states to bind substrate effectively. Deviations from this optimum—especially extreme pH values—alter ionization, disrupt bonds, and can destabilize the overall structure, also reducing activity or causing denaturation. So temperature and pH can dramatically affect how well an enzyme works, and extreme values can denature the enzyme, leading to reduced activity.