Final answer:
It is true that relying on substrate concentration data from the extremes of the range for calculating enzyme velocity is unreliable. Accurate enzyme kinetics require using a range of concentrations to avoid inaccuracies at substrate levels that are too low or high.
Step-by-step explanation:
The statement that using substrate concentration data from only the extremes of the range to calculate enzyme velocity is unreliable is true. When substrate concentrations are either too low or too high, they do not accurately reflect the enzyme's kinetics throughout its entire activity range. At low substrate concentrations, the enzyme may not be sufficiently occupied to provide accurate velocity measurements. On the other hand, at high substrate concentrations, the enzyme becomes saturated, leading to a plateau in the rate of reaction, known as the Vmax (maximum velocity). Therefore, to obtain a reliable measurement of enzyme kinetics and to calculate parameters like Km (the Michaelis constant) or Vmax, it is important to use a wide range of substrate concentrations that fall between these extremes.
In enzyme kinetics, the Michaelis-Menten equation is frequently used to describe how the reaction rate (v) depends on the concentration of the substrate (S). However, this equation has limitations and provides an approximate value of Vmax, not an accurate one. For precise enzyme kinetic studies, steady-state experiments that generate a hyperbolic Michaelis-Menten plot are conducted, varying substrate concentration and keeping enzyme concentration constant. Rates are measured until the enzyme is saturated, and Vmax is approached, but not solely relying on extreme substrate concentration values.