Enzymes

• Most of the food we eat is complex carbohydrates, proteins and lipids. These must be broken down to be absorbed into the body.
• The chemical reactions required to break them down would be too slow without enzymes
• Enzymes are biological catalysts– they speed up chemical reactions.
• Enzymes are required for most of the chemical reactions that occur in organisms. These reactions occur in the breakdown of chemical molecules, which we see in the digestive system
• Enzymes are also involved in the building up of chemical molecules elsewhere in the body.
• Enzymes are proteins that have a complex 3D shape. Each enzyme has a region called an active site.

  The substrate – the molecule or molecules taking part in the chemical reaction – fits into the active site. Once bound to the active site, the chemical reaction takes place .

  
• In an organism, the active site of each enzyme is a different shape. It is a perfect match to the shape of the substrate molecule, or molecules. This is essential to the enzyme being able to work. One enzyme is therefore specific to one substrate's chemical reaction, or type of chemical reaction.

  This theory for the way in which enzymes work is called the lock and key theory
• Factors affecting ENzymes: Temperature

  At low temperatures, the number of successful collisions between the enzyme and substrate is reduced because their molecular movement decreases. The reaction is slow.

  The human body is maintained at 37°C as this is the temperature at which the enzymes in our body work best. This is not true of the enzymes in all organisms.
• Factors affecting Enzyme: Temperature

  Higher temperatures disrupt the shape of the active site, which will reduce its activity, or prevent it from working. The enzyme will have been denatured.

  Enzymes therefore work best at a particular temperature.
• The human body is maintained at 37°C as this is the temperature at which the enzymes in our body work best. This is not true of the enzymes in all organisms.

  Higher temperatures disrupt the shape of the active site, which will reduce its activity, or prevent it from working. The enzyme will have been denatured.

  Enzymes therefore work best at a particular temperature
• The groups of enzymes involved in the breakdown of food are:

  Carbohydrases break down carbohydrates into simple sugars
• Proteases break down proteins into amino acids
• Lipases break down lipids into fatty acids and glycerol