Final answer:
Lowering an enzyme's temperature below its optimal level results in reduced activity and metabolic rates due to decreased kinetic energy and fewer effective collisions between enzyme and substrate.
Step-by-step explanation:
When the temperature of an enzyme is lowered much cooler than its optimal temperature, the rate at which it catalyzes reactions decreases. This is due to a reduction in kinetic energy, which results in fewer effective collisions between the enzyme and its substrate. Enzymes function best at a certain optimal temperature, around 37°C for those in the human body. However, as the temperature drops, the enzymes' activity reduces, and at temperatures close to 0°C, most enzymes become totally inactive. This decrease in enzyme activity has direct consequences on metabolic rates and is utilized in processes like food preservation since it slows down the degradation caused by microbial enzymes.