Final answer:
Enzyme activity is highly dependent on pH, temperature, substrate and enzyme concentrations, and is inhibited by competitive inhibitors and heavy metals like lead. Deviations from optimum conditions, such as extreme pH or temperatures, can denature enzymes, while inhibitor presence can decrease activity.
Step-by-step explanation:
Enzyme activity is significantly influenced by several factors including pH, temperature, substrate concentration, enzyme concentration, competitive inhibitors, and heavy metals. An enzyme's optimal activity is usually at specific pH and temperature values; deviation from these conditions can denature the protein, thus affecting its activity. At extreme pH levels or high temperatures, enzymes lose their three-dimensional structure which is crucial for their catalytic function.
Enzyme activity increases with substrate concentration up to a saturation point beyond which additional substrate doesn't further increase the reaction rate. Furthermore, higher enzyme concentrations generally lead to increased reaction rates, given that substrate is not limited. Competitive inhibitors decrease enzyme activity by competing with the substrate for the active site, while noncompetitive inhibitors like lead (Pb²+) bind to other parts of the enzyme, reducing its activity regardless of substrate concentration.
Environmental conditions dictate the efficiency of an enzyme, with some being resistant to adverse conditions such as extremophiles adapted to high temperatures or various pH conditions. These adjustments are significant not only for understanding the enzyme's behavior under cellular conditions but also for potential allosteric regulation or interference by poisons and toxic substances.