Enzyme Structure and Function. Protein catalysts. Enzymes are Catalysts. This means that enzymes help speed up chemical reactions. How? Enzymes lower the activation energy of a reaction.
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Hydrogen peroxide (substrate) binds to enzyme and is broken down (reaction occurs-bubbling observed.)
Metal ion gets in the way and hydrogen peroxide cannot bind to the enzyme. Reaction either doesn’t occur or occurs at a slower rate. (Not all enzymes are blocked.)
Not all enzymes have the same “optimal” pH. Catalase (liver enzyme) is more like chymotrypsin. However, pepsin (a stomach enzyme) functions best at a low (acidic) pH. At pH 1, pepsin is in it’s functional shape; it would be able to bind to its substate. At pH 5, the enzyme’s shape is different and it no longer has an active site able to bind the substrate. The change in enzyme activity is observed as a difference in reaction rate.
Shape of active site changes (substrate can’t bind)
Slower reaction due to fewer collisions