Question

What did German biochemist Emil Fisher do?
A. He gave the operon model
B. He compares the fit between enzyme-substrate to lock and key
C. He proposed the theory of competitive inhibition
D. He proposed the feedback inhibition theory.

Answer 1

Hint: A chemical reaction to take place, a catalyst is needed. In our body, several enzymes act as catalysts. It drives metabolic reactions. There are several theories about the functioning of enzymes as catalysts.

Complete answer: An enzyme that drives a reaction is made up of proteins. It acts on a substrate molecule and finally becomes the product. Emil Fischer was a German biochemist who proposed a theory of working of these enzymes. It is known as a lock and key mechanism. In this theory, he said that an enzyme acts as a lock and only a specific substrate reacts with a particular enzyme just like the suitable key. It means that enzymes are specific for their substrates. There is a site in every enzyme called an active site that binds with the substrate. When the substrate binds to the active site the conformational change happens and it becomes an enzyme-substrate complex which finally leads to the formation of products. Even though it described the specificity of enzyme lock and key model could not answer why there is a conformational change after the binding of substrate to the active site. Another theory named induced fit theory later replaced the lock and key mechanism theory. This theory says that enzyme conformation changes when the substrate binds to the active site.
Hence, the correct option is B.

Note: Enzymes are made up of proteins they can be inhibited by certain molecules. In competitive inhibition, a molecule that is similar to the substrate can bind to the enzyme. An example of this is the enzyme succinic dehydrogenase inhibited by malonate. The original substrate of this enzyme is succinate.