Enzymes

Enzymes are essential because they increase reaction rates to levels necessary to sustain life.

The active site of an enzyme has a specific shape that is complementary to its substrate. The substrate binds to the active site to form an enzyme-substrate complex, resulting in the formation of products.

At very high temperatures, the enzyme's structure is irreversibly altered (denatured) by breaking the bonds that hold the enzyme together, causing the active site to change shape. This prevents the substrate from binding. An example is boiling an egg; the egg white proteins (enzymes) denature, causing it to solidify.

Changes in pH can disrupt the bonds holding the enzyme together, altering the shape of the active site and preventing substrate binding. Extreme pH values can denature the enzyme.

Enzymes are specific because their active site has a unique shape that only fits a specific substrate, like a lock and key. Only the correctly shaped substrate can bind to the active site and undergo a reaction.

Increasing temperature increases the kinetic energy of molecules, leading to more frequent and forceful collisions between enzyme and substrate. This increases the rate of reaction until the optimum temperature is reached. However, beyond this point, denaturation starts to occur.

Extreme pH levels can disrupt the ionic and hydrogen bonds that maintain the enzyme's 3D structure. This change in shape alters the active site, preventing the substrate from binding and leading to denaturation. An example is how changes in blood pH affect the activity of enzymes involved in respiration.

As substrate concentration increases, enzyme activity increases until all active sites are occupied (saturated). After this point, increasing substrate concentration no longer increases the reaction rate.