Biology Chapter on Catalysis and Enzymes

Catalysis and Enzymes

• Enzymes are protein molecules that speed up chemical reactions in cells.
• They lower the activation energy required for a reaction to occur.
• Enzymes are specific, catalyzing only 1 or 2 reactions at most, unlike inorganic catalysts.
• Enzymes work best at specific temperatures and pH levels.
• High temperatures and extreme pH levels can denature (inactivate) enzymes.
• Enzymes are also affected by heavy metals and poisons.

Activation Energy

• Activation energy is the minimum energy required for a reaction to occur.
• Enzymes reduce the activation energy requirement by providing an alternative reaction pathway.
• Collisions between molecules must have sufficient energy and proper orientation for a reaction to occur.
• Enzymes help by making these collisions more likely.

Hydrogen Peroxide Breakdown

• Hydrogen peroxide (H₂O₂) breaks down into water and oxygen (O₂).
• Manganese dioxide (MnO₂) is an inorganic catalyst that speeds up this reaction.
• Catalase is an enzyme that can also catalyze hydrogen peroxide breakdown, often much faster than inorganic catalysts.

Effect of temperature and pH

• Enzyme activity is affected by temperature.
• Increasing temperature initially increases enzyme activity, but high temperatures can denature the enzyme.
• Enzyme activity is also affected by pH.
• Most enzymes function best near a neutral pH of 7; some function best at acidic or alkaline conditions.
• Heavy metals and poisons can inactivate enzymes.