About the lock and key model of enzyme

[rexsun]

Hi everyone, I'm studying enzyme at this moment and I want to ask about the lock and key model.
In the textbook, the enzyme is described as the lock and the substrates keys, yet I think this description is confusing.
I think the logic could also go this way: the enzyme is the key and substrates are locks. Each time enzyme catalyses a substrate it breaks the lock. The enzyme, just as a key, will not change its shape after the reaction, while the lock is now broken.
What do you think?
Perhaps I have misunderstood some of the materials so came up with this idea... Can anyone tell me why the enzyme is the lock?
Thanks much!

 

[Muhammad Amer]

You are trying to apply the concept of "A key that unlocks many doors is a master key, but a lock that is opened by many keys is a bad lock," yet this is not how the model is described. Perhaps that is why this model is not as appreciated as the induced fit model; it makes much more sense for the key to be the enzyme, because it remains intact after binding with the substrate, while the substrate is logically assumed to have been unlocked into its smaller sub-units. Sadly, this is not the case. The lock and key model is very simple and lacks much logic. It simply states that the substrate fits into the active site of an enzyme the way a key fits inside a lock, the substrate has a specific shape that fits inside the enzyme's active site. Presumably, the enzyme is the lock and the substrate is the key.

If biology concepts get too confusing, try looking them up in a previous exam, answer the question as you've understood the concept and go back to the marking scheme to review any misconceptions.