Enzyme Reaction Rates: pH — Effects & Examples

The Ideal pH Range

Enzyme activity is influenced by pH, temperature, and the substrate concentration of the solution. Depending on the type of enzyme, the pH will have a different impact on the rate of reaction.

All enzymes have specific pH dependencies. If the enzyme is typically found in the stomach, it will probably work best in an acidic environment. If this stomach enzyme is thrown into a neutral or basic pH, it will have a much slower rate of reaction because it is outside of the enzyme's ideal pH range.

If the pH is either too high or too low, the rate decreases dramatically. Once the pH is too far away from the ideal range, the enzyme will become denatured and permanently change shape. This is why it is important for organisms to maintain homeostasis.

$$\color{#8925AE}{\text{Vocabulary Review:}}$$

$\color{#8925AE}{\text{Enzyme}}$ : A protein that acts like a catalyst. It speeds up biological reactions but is not used up during the reaction

$\color{#8925AE}{\text{Activation Energy}}$ : Minimum amount of energy needed to begin a chemical reaction

$\color{#8925AE}{\text{Catalyst}}$ : A substance that speeds up reactions but is not used up during the reaction

$\color{#8925AE}{\text{Substrate}}$ : Molecules that a specific enzyme binds to and recognizes. They are transformed during the reaction

What Effect Does pH Have on Enzyme Function?

Enzymes are picky molecules. They work within a very specific range of conditions and fall apart (literally) when those conditions are violated.

One of these conditions is pH (the concentration of hydrogen ions in a solution).

Every enzyme molecule has an optimum pH—the pH at which they work best. The rate of reaction is greatest at the optimum pH.

So, what happens to enzymes outside their optimal pH range? Why do they stop working?

Recall that enzymes are proteins made of amino acids. The side chain of each amino acid determines how the protein folds and what shape it takes.

The shape of an enzyme is fundamental to its ability to work. So, damaged enzymes are ones whose shapes have been altered in some way. Damaged enzymes no longer have a lock-and-key fit with their substrate molecules, which means they can't catalyze the reaction.

When an enzyme is denatured, it essentially melts and loses its shape. Denaturation can be caused by any change in an enzyme's narrow pH range.

Key Vocabulary:

1. Enzyme
2. pH
3. Optimum
4. Denature
5. Active site
6. Substrate

(Video) How Enzymes Denature

by FuseSchool

Many factors can change how enzymes and substrates fit together.

Explore how movement away from an enzyme's optimal pH affects that enzyme's performance with this video.

(Video) Effect of Temperature and pH on Enzyme Activity

by Ms Cooper's A level Biology

pH is one of the factors that affects the activity rate of an enzyme-catalyzed reaction.

This video explains what happens to enzymes when they are placed outside of their optimal pH range and shows some examples of enzymes that catalyze chemical reactions at different pH levels.