Hey everyone, Happy Easter! Hope you all are enjoying the holidays as much as I am! Continuing on our enzymes topic today, we will be discussing the differences between the Lock & Key and Induced Fit hypothesis. Let’s jump right in!

Lock & Key Hypothesis

The Lock & Key hypothesis explains the idea of enzyme specificity by stating that the shape of the key being the substrate is complimentary to the shape of the lock which is the enzyme’s active site. It is a rigid hypothesis as it makes note that the active site of the enzyme is the exact same shape as the key and thus fits precisely. When this occur the enzyme-substrate complex form, which then leads to the formation of the products that have a different shape from the substrate thus prevents reattaching to the enzyme’s active site. This hypothesis does not only explain the idea of enzyme specificity but also why high temperatures denature enzymes and also why some substances can inhibit enzymes. The main problem with this hypothesis was that it was too rigid and in actuality the enzyme’s active site and substrate were not exactly the same. I found some really cool animations but they refuse to download so please see the link below for cool animations on this topic.


Induced Fit Hypothesis

The Induced Fit hypothesis was put forth after the Lock & key and instead of the enzyme’s active site being rigid this hypothesis states that the enzyme’s active site changes shape to ‘better fit’ the substrate. It is said that as the substrate gets closer to the enzyme’s active site it induces slight change in shape of the enzyme and thus allowing the active site to become totally complimentary. Not only does this occur but the theory also states that there is a change in the enzyme’s conformation as well.



So today we looked at the differences between both the Lock & Key and Induced Fit hypothesis and then we went into understanding what they both discussed. Now we are going to sum up all of this by just recapping of the main difference between the two. The Lock and key model of enzyme substrate binding shows that the active site of the unbound enzyme is precise in shape to the substrate; however, the induced fit model of enzyme substrate binding shows that the enzyme changes shape on contact with substrate.

Once again guys thanks for taking the time off to read this blog post, please go ahead and like, comment and share. Happy Blogging!


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Youtube: BiochemJM

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