The rate of an enzyme catalyzed reaction depends: a) upon substrate concentration, temperature and pH. b) only on substrate concentration and pH, but not on temperature. c) only on pH and temperature, but not on substrate concentration. d) only on temperature, but not on pH and substrate concentration.

The rate of an enzyme-catalyzed reaction is influenced by several critical environmental and chemical factors. Temperature significantly affects reaction rates; as temperature increases, molecular collisions between enzymes and substrates become more frequent, though excessive heat leads to denaturation. pH levels also play a vital role, as each enzyme has an optimal pH range; deviations from this range can disrupt the enzyme's tertiary structure and active site. Furthermore, substrate concentration is a primary determinant; the reaction rate increases with higher substrate levels until the enzyme's active sites become saturated, at which point the rate plateaus. Other factors, such as enzyme concentration and the presence of inhibitors, also modulate these biochemical processes. Therefore, the reaction rate depends on substrate concentration, temperature, and pH simultaneously.