Short Answer

Induced-fit model of enzyme action explains how enzymes work by changing their shape slightly when a substrate binds to them. In this model, the enzyme is flexible, not rigid. When the correct substrate comes close, the enzyme adjusts its active site to fit the substrate properly.

This shape change helps the enzyme hold the substrate tightly and speed up the reaction. The induced-fit model explains enzyme specificity and efficiency better than earlier models and helps us understand how enzymes work accurately in living cells.

Detailed Explanation :

Induced-fit model of enzyme action

The induced-fit model of enzyme action is an advanced and more accurate explanation of how enzymes work in living organisms. This model was proposed to overcome the limitations of the lock-and-key model. According to the induced-fit model, enzymes are not rigid structures. Instead, they are flexible molecules that change their shape slightly when a substrate binds to them. This change in shape helps the enzyme perform its function more efficiently.

Basic idea of the induced-fit model

Enzymes are protein molecules with a flexible structure.
The active site of the enzyme is not a perfect match initially.
When the correct substrate approaches, the enzyme changes its shape.
This shape change improves the fit between enzyme and substrate.
The enzyme and substrate fit together closely after binding.

This process is called induced fit because the binding of the substrate induces a change in the shape of the enzyme.

Role of the active site

The active site is the region of the enzyme where the substrate binds.
In the induced-fit model, the active site is flexible.
When the substrate binds, the active site adjusts its shape.
This adjustment brings important groups of the enzyme closer to the substrate.
Proper positioning helps the reaction occur easily.

The flexibility of the active site is the key feature of this model.

Formation of enzyme–substrate complex

The substrate approaches the enzyme.
Weak interactions begin between enzyme and substrate.
The enzyme changes its shape slightly.
A tight enzyme–substrate complex is formed.
This complex holds the substrate firmly in the correct position.

This close binding increases the chance of reaction and ensures accuracy.

How the induced-fit model lowers activation energy

Every chemical reaction needs activation energy to start.
Activation energy is the energy barrier of a reaction.
The induced-fit model helps lower this energy.

This happens because:

The enzyme stresses or weakens bonds in the substrate.
Reacting groups are brought closer together.
The substrate is held in the best position for reaction.

As a result, the reaction occurs faster and at normal body temperature.

Conversion of substrate into product

Once the enzyme–substrate complex is formed, the reaction begins.
Old bonds in the substrate break.
New bonds are formed to create product molecules.
The enzyme helps guide this process without being consumed.

The product molecules no longer fit the active site properly and are released.

Release and reuse of enzyme

After the reaction, the products leave the enzyme.
The enzyme returns to its original shape.
The enzyme is free to bind another substrate.
One enzyme can repeat this process many times.

This reuse makes enzymes highly efficient biological molecules.

Specificity explained by induced-fit model

Only the correct substrate can induce the right shape change.
Wrong substrates cannot cause proper fitting.
This ensures high specificity of enzyme action.

Thus, the induced-fit model explains why enzymes act only on specific substrates while still being flexible.

Comparison with lock-and-key model

Lock-and-key model assumes enzyme shape is rigid.
Induced-fit model assumes enzyme shape is flexible.
Lock-and-key explains basic specificity.
Induced-fit explains flexibility and efficiency.
Induced-fit model explains more enzyme reactions accurately.

Due to this, the induced-fit model is considered more realistic.

Importance of induced-fit model in metabolism

Metabolism involves many complex reactions.
Each reaction needs a specific enzyme.
Induced-fit allows enzymes to adapt slightly.
This increases accuracy and speed of reactions.
It prevents unwanted side reactions.

Thus, metabolism remains smooth and controlled.

Examples of induced-fit enzyme action

Digestive enzymes change shape while breaking food molecules.
Enzymes in respiration adjust to different substrates.
Enzymes in photosynthesis work efficiently due to induced fit.

These examples show the importance of enzyme flexibility.

Importance in living organisms

Allows reactions at normal body temperature.
Saves energy for the cell.
Supports growth, repair, and survival.
Helps organisms adapt to changes.
Maintains balance inside cells.

Without induced-fit enzyme action, many life processes would be too slow or inefficient.

Medical and biological importance

Helps understand enzyme-related diseases.
Explains how drugs bind to enzymes.
Used in drug design and treatment.
Helps in biotechnology and research.
Important in understanding metabolic disorders.

Conclusion

The induced-fit model of enzyme action explains that enzymes are flexible molecules that change their shape when a substrate binds to them. This shape change allows a better fit, lowers activation energy, and speeds up chemical reactions. The model explains enzyme specificity, efficiency, and adaptability more accurately than earlier models. By allowing precise and fast reactions under mild conditions, the induced-fit model helps explain how enzymes control metabolism and support life processes effectively.