Question

enzymes are described as being like a lock-and-key. what does this mean?
each enzyme has many substrates.
each enzyme unlocks many chemical reactions.
each enzyme catalyzes one type of reaction.
each enzyme changes the shape of a substrate.

Explanation:

The lock - and - key model of enzymes implies that each enzyme has a specific active site (like a lock) that fits only one type of substrate (like a key). Let's analyze each option:

• Option 1: Enzymes are specific to their substrates, so an enzyme doesn't have many substrates. This is incorrect.
• Option 2: Enzymes are specific catalysts; each enzyme typically catalyzes one type of reaction (or acts on one type of substrate), which aligns with the lock - and - key model.
• Option 3: Enzymes are specific, so they don't unlock many chemical reactions. This is incorrect.
• Option 4: Enzymes don't change the shape of the substrate in the context of the lock - and - key model (the induced - fit model is different, but here we are dealing with lock - and - key). This is incorrect.

Answer:

The correct option is the one with the text "Each enzyme catalyzes one type of reaction." (Assuming the option with this text is the second one in the list of options as per the image description)