What substance accelerates a chemical reaction in a cell and is a biological catalyst?

Enzymes are biological catalysts. There are optimal temperatures and pH values ​​at which their activity is high. Enzymes are also proteins and are usually denatured above about 45ºC.

Enzymes are essential for breathing. Aerobic breathing releases energy from glucose. As the temperature rises, the reaction rate also occurs. But very high temperatures denature the enzymes. Changes in pH change the shape of the enzyme. Different enzymes work better at different pH values. The optimal pH for an enzyme depends on where it normally works. For example, intestinal enzymes have an optimum pH of about 7.5. The enzymes in the stomach have an optimal pH of about 2.