D, substrate is to active site
Substrate to the enzyme.
Enzymes are the bio catalyst that can increase the rate of the bio chemical reaction. Enzymes has the ability to work at the specific pH and temperature.
The enzymes follow the lock and key hypothesis. The substrate should fit into the active site of the enzyme as the key fits into its lock. The enzyme has high specificity for its substrate and should be structurally selective in nature.
Thus, the answer is substrate to the enzyme.
The correct answer is option option D
The enzyme-substrate model resembles the lock and key model. The key is specific to the lock and it cannot fit into some other lock.
As like that of lock and key, the substrate is specific to the active sites. The substrate binds to the active as the key fits in the lock.
In this way the product formation takes place.
A substrate is a necessary component for an enzyme to become active. It is a specific shape that fits perfectly into an Active Site on the enzyme.