Introduction and Mechanism of Enzymes

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Enzymes are proteins that catalyze chemical reactions that are essential for life. They help the body to digest food, break down fats and carbohydrate into energy, make hormones, build muscle, and protect against disease.

During the process, enzymes form bonds between amino acid residues on their surfaces and substrate molecules. This bond formation leads to an enzyme-substrate complex (ES).


Enzymes are proteins that act as catalysts, which means they help increase the rate of chemical reactions. They do this by decreasing the amount of energy required to begin a reaction, which is called activation energy.

They are a critical component of many metabolic processes in our bodies, including DNA replication and the liver’s detoxification functions. Without enzymes, these reactions would take much longer to complete and not happen at the rates needed to sustain life.

One way they do this is by binding to substrate molecules in key locations in their structure, called active sites. They are highly specific, and only bind certain substrates for particular reactions.

Several factors affect the ability of enzymes to bind to substrates, including temperature, pH and substrate concentration. They also rely on metal ions, cofactors and other molecules to assist with their catalysis.

As substrates bind to an enzyme’s active site, it may change shape slightly. This change helps the enzyme grasp the substrate more tightly and ready itself to start the reaction. This process is called induced fit.

Substrate Binding

A key part of the mechanism of enzymes is substrate binding. Substrate binding helps the enzyme bind to specific molecules that are crucial for its function.

Each enzyme has a unique active site, which is a groove or pocket in the enzyme that is optimised to bind a particular substrate and catalyse a reaction. This is important as without this key structural feature, most metabolic reactions would take a long time to occur, or not happen at all.

Substrate binding also plays a role in lowering the activation energy required for a reaction. This is achieved by either bringing two substrate molecules together in the correct orientation, creating an environment inside the active site that’s favorable to a reaction (for example, one that’s slightly acidic or non-polar), or bending substrate molecules in a way that facilitates bond-breaking, helping them reach the transition state.

Activation Energy

In all chemical reactions, a certain amount of energy must be added before the reaction can start. The energy is called activation energy and it can be either positive or negative depending on the bonds that are broken or formed in the reactants.

Enzymes lower the activation energy required for a reaction to occur. This is done through a variety of mechanisms, but most commonly involves binding to the substrate.

When an enzyme binds to a substrate it provides them with a specific shape that allows them to fit in the enzyme’s active site. This is known as induced fit.

The enzyme-substrate complex also lowers the activation energy of a reaction by rearranging the electrons in the substrate so that they are in areas that favor a reaction.

This lowering of the activation energy is done by straining the substrate and forcing it to a transition state that favors the reaction. The substrate is then used as a catalyst for the reaction to happen.


Enzymes are catalysts, which speed up chemical reactions by lowering the energy needed to get them going. They are essential to the chemical processes that turn raw materials into useful products, such as food, medicines, and plastics.

They also help humans in a variety of ways. For example, enzymes play a key role in the human body by creating signals that move our limbs and helping us digest our food.

The mechanism of catalysis is complex and involves a series of interactions between substrates, the enzyme, and the reaction intermediates. These interactions include electrostatic interactions, ionic interactions, and hydrogen bonding.

One important feature of catalysis is substrate specificity, which is largely the result of amino acid residues in the enzyme’s active site. These residues have various shapes and charges, which ensure they bind to a single substrate molecule. This tight binding lowers the energy needed to activate the transition state, allowing the reaction to happen more quickly.

Introduction and Mechanism of Enzymes

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