Introduction
Enzymes are crucial for life as they facilitate and accelerate biochemical reactions necessary for cellular function. They are biological catalysts, meaning they increase the rate of chemical reactions without being consumed or permanently altered in the process. This study note will delve into the structure and function of enzymes, the enzyme-substrate complex, how enzymes lower activation energy, and factors affecting enzyme activity, all aligned with the International Baccalaureate (IB) syllabus for Biology.
Structure of Enzymes
Biological Catalysts
- Biological: Enzymes function within living systems.
- Catalysts: They speed up chemical reactions without being used up or undergoing permanent change.
Active Site and Specificity
- Active Site: The region on an enzyme where the substrate binds.
- Specificity: The active site has a specific shape that fits only specific substrates, akin to a lock and key mechanism.
- Globular Proteins: Enzymes are typically globular proteins, ensuring their active sites are correctly oriented for substrate binding.
Enzyme specificity means that thousands of different enzymes are required in an organism to carry out various biochemical reactions.
Enzyme-Substrate Complex
- Binding: The substrate binds to the enzyme's active site.
- Orientation and Speed: Substrates must collide with the active site in the correct orientation and speed for a reaction to occur.
- Transitional State: The substrate enters a transitional state when bound to the enzyme.
- Product Formation: The enzyme catalyzes the conversion of the substrate into the product.
- Release: The product is released, and the enzyme is free to catalyze another reaction.
Simple Reaction Equation
The enzyme-catalyzed reaction can be summarized as:
$$ E + S \rightarrow ES \rightarrow E + P $$
Where (E) is the enzyme, (S) is the substrate, (ES) is the enzyme-substrate complex, and (P) is the product.
Enzymes and Activation Energy
Energy Changes in Reactions
- Exergonic Reactions: Release energy.
- Endergonic Reactions: Absorb energy.
Activation Energy
- Definition: The minimum amount of energy required for a reaction to proceed.
- Role of Enzymes: Enzymes lower the activation energy by destabilizing bonds in the substrate, thus speeding up the reaction.
For instance, the enzyme catalase speeds up the decomposition of hydrogen peroxide into water and oxygen, a reaction essential for cellular protection against oxidative damage.
