Question

using your notes, fill in the blank and answer the questions below.
1 what is the \lock and key\ model of enzyme action, and how does it explain enzyme specificity?
2 how does the shape of an enzymes active site determine its specificity for a particular substrate? use the lock and key model to support your explanation.

Explanation:

The "lock and key" model of enzyme action posits that the enzyme (lock) has a specifically shaped active site that precisely fits the substrate (key). Just as a key has a unique shape that fits only one lock, each enzyme's active site has a unique shape that allows it to bind only to a specific substrate. This complementary shape - specificity ensures that only the correct substrate can bind to the enzyme's active site, explaining enzyme specificity. The shape of the enzyme's active site is determined by its amino - acid sequence and the resulting three - dimensional structure. If the active site's shape is altered (e.g., by denaturation), the substrate can no longer bind, further emphasizing the importance of the active site's shape in substrate recognition.

Answer:

1. The “lock and key” model of enzyme action is a theory where the enzyme (like a lock) has an active site with a specific shape that exactly matches the shape of its substrate (like a key). It explains enzyme specificity because only the substrate with the complementary shape can fit into the enzyme’s active site, similar to how only one key fits a particular lock.
2. The shape of an enzyme’s active site is complementary to the shape of its specific substrate. Using the lock and key model, if the active site (lock) has a unique shape, only the substrate (key) with the matching shape can bind. The amino - acid sequence of the enzyme determines the active site’s shape. For example, if an enzyme’s active site is shaped to fit a glucose molecule (substrate), other molecules (like fructose, which has a slightly different shape) cannot bind effectively, thus determining the enzyme’s specificity for glucose.