Question

Enzymes and their substrates are often compared to a lock and key. This is called the lock and key model. Label the lock and key.

a) Lock: Enzyme, Key: Substrate.
b) Lock: Substrate, Key: Enzyme.
c) Lock: Reactant, Key: Product.
d) Lock: Inhibitor, Key: Catalyst.

Answer 1

In the lock-and-key model, the enzyme serves as the lock and the substrate as the key. The correct answer to the question is 'a) Lock: Enzyme, Key: Substrate.'

Step-by-step explanation:

The comparison of enzymes and their substrates to a lock and key is an analogy to describe the specificity of enzyme action. According to the lock-and-key model, the enzyme acts as the lock, and the substrate acts as the key. This model assumes a fixed shape of the enzyme's active site, making it complementary to the shape of the substrate, much like how a specific key fits into a specific lock. Therefore, the correct labeling would be:

1. Lock: Enzyme, Key: Substrate.

Enzymes are highly specific and will generally only bind to substrates that fit exactly into their active site, forming an enzyme-substrate complex necessary for the catalytic reaction to occur. The induced fit hypothesis further explains that though the enzyme's active site is somewhat flexible, allowing it to adjust to the shape of the substrate, this flexibility does not negate the specificity of the enzyme, it only enhances the interaction between the enzyme and substrate.