Lock and Key Theory vs Induced Fit Theory

The page discusses two important models of enzyme-substrate interaction: the lock and key theory and the induced fit model.

Lock and Key Theory

The lock and key theory proposes that enzymes have specific active sites that only bind with substrates that fit precisely, similar to how a key fits into a lock.

Definition: The lock and key theory states that enzymes have specific active sites which will 'only' bind with substrates that fit these active sites.

Induced Fit Theory

The induced fit model suggests that enzyme active sites and substrates do not have precise complementary shapes initially. Instead, the enzyme's active site undergoes a conformational change upon substrate binding.

Definition: The induced fit theory states that enzyme active sites and substrates do not have precise complementary shapes. This means more than one type of substrate could fit into the enzyme.

Highlight: The induced fit model involves a conformational shape change caused by bonding between enzyme R-Groups and the substrate.

Temperature Effects on Enzyme Activity

The page also explains how temperature affects enzyme-controlled reactions:

1. At low temperatures, kinetic energy is low, resulting in fewer collisions and a lower reaction rate.
2. At optimum temperature, the enzyme is most efficient, with the highest rate of reaction due to optimal kinetic energy and frequent collisions.
3. At high temperatures, the enzyme's bonds break, causing denaturation and a decrease in reaction rate.

Example: The effect of temperature on enzyme activity is illustrated through three stages: low temperature (A), optimum temperature (B), and high temperature (C).

Activation Energy and Reaction Types

The page introduces the concept of activation energy and describes two types of enzyme-catalyzed reactions:

1. Anabolic reactions: Two substrate molecules are joined together.
2. Catabolic reactions: The substrate molecule is broken down.

Vocabulary: Activation energy is the minimum amount of energy needed to start a chemical reaction.

Enzyme Structure and Bonding

The page details the various bonds that contribute to an enzyme's tertiary structure:

• Ionic bonding
• Disulfide bonds
• Hydrophilic/Hydrophobic interactions
• Hydrogen bonds

Highlight: The active site of an enzyme is determined by its tertiary structure, which involves the folding and coiling of amino acids.

Factors Affecting Enzyme Activity

The page discusses several factors that influence enzyme activity:

1. pH Levels: Each enzyme has an optimum pH, with most human enzymes working best at pH 7.
2. Substrate Concentration: As substrate concentration increases, the reaction rate increases until enzyme concentration becomes a limiting factor.
3. Intracellular Enzymes: Enzymes can be found in various locations within cells, including the cytoplasm, bound to organelles, or within organelles.

Example: The effect of pH on enzyme activity is explained through three stages: low pH (A), optimum pH (B), and high pH (C).

This comprehensive overview provides a solid foundation for understanding enzyme function and the factors that influence their activity in biological systems.