Enzymes: The Chemistry of Life

Terminology

• Denaturation: Occurs when the shape of the enzyme changes, and it can no longer function.
• Enzymes: Organic catalysts.
• Catalyst: A substance that speeds up a chemical reaction without being used up in the reaction.
• Organic Catalyst: Contains the element carbon and is usually protein in nature.
• Optimum Rate: The rate at which the most product is formed in the shortest space of time.
• Co-enzyme: The non-protein organic partner of enzymes.

What are Enzymes?

• Enzymes are organic catalysts.
• A catalyst is a substance that speeds up a chemical reaction without being used up in the reaction.
• An organic catalyst is one that contains the element carbon and is usually protein in nature.
• Enzymes are protein molecules that control metabolic reactions.

Enzymes

• They act as catalysts because they increase or slow down the rate of a reaction.
• Regulate almost every reaction in the human body.
• Are specific in their action; each enzyme regulates one particular reaction or type of reaction.
• They are not altered by the reaction and can function repeatedly.

Lock-and-Key Model

• The lock-and-key model of enzyme action explains how specific enzymes act on specific substrate molecules.
• The theory states that, like a specific key fitting into a specific lock, each enzyme targets a specific substrate that fits into its active site.

Lock and Key Theory

• A - the substrate fits into the active site of the enzyme forming
• B - an enzyme-substrate complex
• C - a chemical reaction occurs, and the substrate changes shape
• D - the enzyme and substrate separate, and the enzyme can now react with more of the substrate

Co-Enzymes

• Most enzymes need the help of a partner.
• This partner is organic and non-protein in nature.
• The partner is called a co-enzyme.
• The co-enzyme is loosely bound to the enzyme.

Effect of Temperature on Enzyme Activity

• Enzymes are proteins and are affected by temperature and pH.
• Enzymes work best at an optimum temperature, which is 37°C in the human body.
• At temperatures higher than body temperature, the reaction rate slows down.
• At extremely high temperatures, the enzyme structure is destroyed, preventing binding with the substrate molecule.
• At low temperatures, the enzyme becomes inactive, and the reaction rate slows down, but the structure is not permanently destroyed.

Effect of Temperature on Enzyme Activity (Graph Explanation)

• As temperature increases, the reaction rate also increases until about 37°C, where enzyme activity is at its maximum (optimum temperature).
• As the temperature increases further, enzyme activity decreases because the temperature is too high, leading to enzyme denaturation.

Effect of pH on Enzyme Activity

• Enzymes are sensitive to pH.
• Most enzymes work best in pH-neutral conditions.
• Extreme pH conditions can permanently denature enzymes.

Effect of pH on Enzyme Activity (Graph Explanation)

• The graph shows that enzyme activity peaks at a certain pH (optimum pH).
• If the pH is lower or higher than this optimum pH, enzyme activity decreases because the enzyme becomes denatured.

Effect of pH on Enzyme Activity

• The shape of the enzyme changes, and enzyme activity slows down or stops.
• Enzymes are very specific; a certain enzyme will only work in a certain pH.
• Salivary amylase only works in an alkaline medium.

The Use of Enzymes in Industry

1. Meat tenderizer
2. Remove hair from skins
3. Making of beer, wine, and vinegar
4. Making chocolate and syrups
5. Making washing powders

Activity 1

1. Explain why:
* (a) the presence of protease and lipase would make the washing powder more effective than ordinary detergent
1. Explain why:
* (b) the powder should not be used in boiling water

Activity 1

• Silk is a material made from protein.
• Explain why the biological washing powder should not be used to wash silk clothes.

Activity 2

• Grade 10 learners investigated the effect of temperature on enzyme activity.
• The following data was collected: Draw a bar graph using the data provided.

Activity 3

• Study the graph below showing the effect of temperature on enzyme activity in an acidic medium.
  3.1 Identify the dependent and independent variable from the graph

Activity 3

3.2 At what temperature does this enzyme work the best?
3.3 What variable is considered constant in the given graph? Say why it must be controlled.