12. explain what takes place in each step of the diagram (each arrow represents a step in the pathway!

Enzymes are proteins in nature which is very important in metabolism and act as catalysts. Specific enzymes perform different functions.

The lock and key model of enzymes were given by Fischer. In this model, the enzyme acts as a lock and the substrate is the key.

The steps of the diagram can be explained by the following:

Therefore, the product is formed by the interaction of enzymes and substrate.

To learn more about enzymes and lock-key theory follow the given link:

link

The enzyme and substrates first join with each other to form a enzyme - substrate complex which then is acted upon by the enzyme to form the product which then detaches from the enzyme.

Explanation:

This is the lock and key hypothesis of the enzyme which states how the enzyme and the substrate specificity takes place. Here it explained that in the first step, the substrate attaches with the enzyme in the specific site that has the complementary structure to that of the substrate, or it has some groups which can temporarily bond with the substrate with the enzyme. This then forms the transient enzyme - substrate complex. This then helps the enzyme to act on the substrate. As the action gets over and the product is formed the product separates from the enzyme.