Catalysts and Enzymes Notes

Catalysts & Enzymes

Activation Energy

• An unstable system, like a rock on a cliff, can remain in that state for a long time.
• Activation energy is the "push" needed to initiate the release of energy.
• Sometimes a small push is sufficient, like a ball on a flat surface.
• Other times, a larger push is required.
• The amount of energy released is the same regardless of the activation energy if the ball falls the same distance.

Catalysts

• Catalysts accelerate chemical reactions.
• They achieve this by reducing the activation energy required.
• With less energy needed to start the reaction, it proceeds more quickly.
• The catalyst itself remains unchanged throughout the reaction.
• The initial and final energy levels of reactants and products are not altered by the catalyst.

Activation Energy & Catalysts

• Catalysts decrease the activation energy required for a reaction to occur.
• Molecules must possess sufficient energy (activation energy) for a reaction to occur quickly.
• Reducing the activation energy is analogous to lowering the height of a hill, allowing a person to roll stones over it at a faster rate.
• Catalysts speed up reactions by reducing this activation energy.

Example of a Catalyst: Platinum (Pt)

• Cars produce carbon monoxide (CO), a toxic gas.
• Platinum in catalytic converters catalyzes the conversion of CO into carbon dioxide (CO2), a non-toxic gas.
• The reaction $2CO + O2 + Pt \rightarrow CO2 + O2 + Pt$ would not happen quickly without platinum.
• The platinum itself is not altered by the reaction.

Energy of Life

• Life necessitates energy.
• Living organisms intake, transform, and release energy through chemical reactions.
• These reactions must occur very rapidly.

Enzymes: Biological Catalysts

• Enzymes are catalysts produced by living organisms.
• They are almost always proteins.
• All cellular life depends on enzymes to accelerate chemical reactions.
• Enzymes reduce activation energies, thus speeding up chemical reactions in living things.

How Enzymes Work

• Enzymes accelerate reactions by lowering the activation energy required.
• The energy of reactants and products remains unchanged, but the activation energy is reduced by the enzyme.

Amylase: An Enzyme Example

• Amylase is an example of an enzyme.
• Potatoes contain starch, which consists of many bound sugar molecules.
• When chewing a potato, amylase (a saliva enzyme) breaks down starch into smaller maltose molecules as part of digestion.
• The body produces amylase.
• Without amylase, it would take years to break down starch.

Catalase: Another Enzyme Example

• Catalase catalyzes the reaction: $2H2O2 + catalase \rightarrow 2H2O + O2 + catalase$