1.4.3 How Enzymes Work

Structure of Enzymes:

• Enzymes have a specific active site, a small region where the reaction occurs. The active site is formed by a few amino acids, creating a unique shape.
• The substrate is the molecule that binds to the enzyme's active site.
• Enzyme specificity means that each enzyme is specific to one substrate, as only that substrate has the complementary shape to fit into the active site.

Lock and Key Model:

• This model suggests that the active site of the enzyme is a specific shape that matches only a particular substrate, much like a key fits into a lock.
• The substrate fits precisely into the active site, forming an enzyme-substrate complex, which allows the reaction to proceed.
• This model explains enzyme specificity, where each enzyme is specific to one type of reaction.

Mechanism of Enzyme Action - Induced Fit Model:

• According to this model, the active site is flexible rather than rigid.
• When the substrate binds to the active site, the enzyme changes shape slightly to fit the substrate more closely. This is known as the induced fit model.
• This conformational change helps to lower the activation energy, making the reaction easier to complete.
• After the reaction, the products are released, and the enzyme returns to its original shape, ready to bind to another substrate.
• The induced fit model provides a more accurate representation of enzyme activity, explaining how the enzyme's structure can adapt to better interact with the substrate.