Match the terms (1) active site, (2) lock-and-key model, and (3) induced-fit model with the following descriptions:
a. the portion of an enzyme where catalytic activity occurs
b. the active site adapts to the shape of a substrate
c. the active site has a rigid shape

Verified step by step guidance

1. Step 1: Understand the term 'active site'. The active site is the specific region of an enzyme where the substrate binds and catalytic activity occurs. Match this description with option (a).
2. Step 2: Understand the 'lock-and-key model'. This model suggests that the active site of an enzyme has a rigid shape that perfectly matches the shape of its substrate, similar to a key fitting into a lock. Match this description with option (c).
3. Step 3: Understand the 'induced-fit model'. This model proposes that the active site of an enzyme is flexible and can adapt its shape to fit the substrate when it binds. Match this description with option (b).
4. Step 4: Review the matches to ensure they align with the definitions and descriptions provided in the problem.
5. Step 5: Confirm the final matches: (1) active site corresponds to (a), (2) lock-and-key model corresponds to (c), and (3) induced-fit model corresponds to (b).

Key Concepts

Active Site

The active site is a specific region on an enzyme where substrate molecules bind and undergo a chemical reaction. This site is crucial for the enzyme's catalytic activity, as it provides the necessary environment for the reaction to occur. The shape and chemical properties of the active site determine the specificity of the enzyme for its substrate.

Lock-and-Key Model

The lock-and-key model is a theory that describes how enzymes and substrates interact. According to this model, the active site of the enzyme (the 'lock') has a specific shape that exactly fits the substrate (the 'key'). This rigid fit explains the specificity of enzymes, as only substrates with the correct shape can bind to the active site and be catalyzed.

Induced-Fit Model

The induced-fit model expands on the lock-and-key model by suggesting that the active site of an enzyme is flexible and can change shape to better fit the substrate upon binding. This adaptability enhances the enzyme's ability to catalyze reactions, as the conformational change can facilitate the transition state and lower the activation energy required for the reaction.