Enzymes (WJEC GCSE Chemistry)

• Enzymes are biological catalysts which speed up the rate of a chemical reaction without being changed or used up in the reaction
  • They are biological because they are made in living cells
• Enzymes catalyse specific reactions and operate under specific conditions
  • They control many reactions which occur in cells, allowing these reactions to occur at much faster speeds than they would without enzymes at relatively low temperatures (such as human body temperature)
  • They are also important in industry as they allow industrial reactions to happen at lower temperatures and pressures than usually needed, saving money and energy
• Important chemical reactions involving enzymes include fermentation, respiration and photosynthesis  

• Enzymes are biological molecules with a specific shape that is held in place by chemical bonds
  • This specific shape is the reason that different enzymes act on specific reactions
• Enzymes typically work within a tight temperature range
  • If the temperature is too low, they still work but there are few successful collisions
  • If the temperature is too high, i.e. over 60 ^oC, the molecule absorbs the thermal energy causing the chemical bonds to break
    • This means that the enzyme loses its shape and can no longer catalyse the reaction
    • This is called denaturing or denaturation
  • Enzymes have an optimum temperature
    • This is the temperature where they are the most effective catalyst, producing the maximum amount of product 

The effect of temperature on the rate of enzyme activity

As temperature increases, the rate of reaction increases until the optimum temperature when it decreases as enzymes are denatured

• Enzymes have several uses including:
  • Food processing
    • Enzymes improve the taste and texture of foods
    • For example, enzymes break starch down into sugar during bread making and convert milk into cheese

Photo by mohamed hassouna on Unsplash 

• • Fermentation
    • Yeast is used to produce alcohol through fermentation
    • The enzyme in yeast breaks glucose down into ethanol and carbon dioxide
  • Medicine
    • Enzymes are used in the production of many medicines including antibiotics and insulin
  • Detergents
    • Enzymes are added to detergents to break down stains, such as blood or grass.
  • Bioethanol production
    • Enzymes are used to produce bioethanol
    • They help break down plant materials into simple sugars that can be fermented into bioethanol