Enzyme Action Models and Factors Affecting Activity
The page discusses two primary models of enzyme action: the lock and key theory and the induced fit model. It also explores various factors that influence enzyme activity.
Lock and Key Theory
The lock and key theory of enzyme action proposes that an enzyme's active site is precisely complementary to its substrate. This model explains enzyme specificity, as only a specific substrate will fit into a particular active site, much like a key fits a lock.
Definition: The lock and key theory states that enzymes have a specific shape that matches their substrate exactly, allowing only certain substrates to fit into the active site.
Induced Fit Model
The induced fit model of enzyme action suggests that the enzyme's active site is not entirely rigid. Instead, it undergoes a conformational change when exposed to a substrate. This model has two advantages over the lock and key theory:
- It explains how enzymes may exhibit broad specificity.
- It provides insight into how catalysis may occur.
Highlight: The induced fit model offers a more flexible understanding of enzyme-substrate interactions, accounting for enzymes that can work with multiple substrates.
Enzyme and Substrate Interaction
Enzymes are globular proteins that act as biological catalysts, speeding up chemical reactions without being consumed. They can be reused and typically function in aqueous solutions.
Vocabulary: Collision frequency refers to the rate at which enzyme and substrate molecules come into contact, which can be increased by enhancing molecular motion or raising particle concentration.
Factors Affecting Enzyme Activity
Temperature
Temperature significantly impacts enzyme activity:
- Low temperatures result in insufficient thermal energy.
- Increasing temperature enhances molecular speed and motion.
- At the optimum temperature, enzyme activity reaches its peak.
- Higher temperatures can cause enzyme denaturation, leading to a loss of shape and activity.
Example: A graph illustrates how enzyme activity increases with temperature up to an optimum point, after which it rapidly declines due to denaturation.
pH
pH affects enzyme activity by altering the charge of the enzyme:
- Changes in pH can diminish the enzyme's ability to bind to the substrate.
- Each enzyme has an optimum pH range for maximum activity.
- Moving outside this range reduces enzyme effectiveness.
Highlight: Maintaining the correct pH is crucial for optimal enzyme function in biological systems and industrial applications.
Substrate Concentration
Substrate concentration influences enzyme activity:
- Increasing substrate concentration generally increases enzyme activity.
- Higher substrate levels increase the chance of enzyme-substrate collisions.
- After a certain point, the rate of activity plateaus due to enzyme saturation.
Example: A graph shows how enzyme activity increases with substrate concentration until it reaches a plateau, demonstrating the concept of enzyme saturation.
