October 6, 2025

What Is The Lock And Key Model

Q: Who proposed the lock and key model?

The lock and key model was proposed by the German chemist Emil Fischer in 1894 to explain the highly specific nature of enzyme-substrate interactions.

Q: Is the lock and key model still considered accurate?

It is considered a foundational but overly simplified model. Modern biochemistry largely favors the 'induced-fit model,' which suggests the enzyme's active site is flexible and changes shape slightly to bind the substrate more securely.

Q: What is the difference between the lock and key and induced-fit models?

The lock and key model assumes a rigid, pre-formed active site. The induced-fit model proposes that the active site is flexible and molds its shape around the substrate after the initial binding occurs.

Q: What part of the enzyme is the 'lock'?

In this analogy, the 'lock' is the enzyme's active site. This is the specific region on the enzyme where the substrate binds and the chemical reaction is catalyzed.

Learn about the lock and key model, a simple analogy used to explain how a specific enzyme binds to its specific substrate to catalyze a biological reaction.

Have More Questions →

What is the Lock and Key Model?

The lock and key model is a simplified analogy used to describe how enzymes work. It proposes that the active site of an enzyme (the lock) has a specific, rigid shape that is perfectly complementary to the shape of its substrate (the key). Only the correctly shaped substrate can fit into the active site.

Section 2: The Principle of Specificity

This model's central principle is enzyme specificity. Just as only one key can open a specific lock, only one type of substrate molecule can bind to the enzyme's active site. This high degree of specificity ensures that enzymes catalyze only the correct biochemical reactions within a cell, preventing unwanted side reactions.

Section 3: A Practical Example

A clear example is the enzyme lactase and its substrate, lactose. The active site of the lactase enzyme is shaped specifically to bind with the lactose sugar molecule. When lactose (the key) fits into the lactase active site (the lock), the enzyme can break lactose down into smaller sugars, glucose and galactose.

Section 4: Importance of the Model

The lock and key model was a crucial first step in understanding enzyme function. While it has been refined by the more flexible induced-fit model, it remains a valuable educational tool for introducing the concepts of enzyme active sites and substrate specificity, which are fundamental to biochemistry and medicine.

Frequently Asked Questions

Who proposed the lock and key model?

Is the lock and key model still considered accurate?

What is the difference between the lock and key and induced-fit models?

What part of the enzyme is the 'lock'?