enzyme

• 1. Anabolic reactions:​Reactions that build up molecules ​
  2. Catabolic reactions:​Reactions that break down molecules​
  3. Metabolism:​Combination of anabolic and catabolic reactions​
  4. Catalyst:​A substance that speeds up reactions without changing the produced substances​​
  5. Metabolic pathway:​Sequence of enzyme controlled reactions​​
  6. Specificity:​Only able to catalyse specific reactions​​
  7. Substrate:​The molecule(s) the enzyme works on​​
  8. Product:Molecule(s) produced by enzymes 
• Enzymes can be defined as biological catalysts.​

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  A catalyst is a substance that speeds up a chemical reaction but remains unchanged itself at the end.​

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  Enzymes are biological catalysts because they are protein molecules made by living cells.​

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• Enzymes are globular proteins and have a teritiary structure. ​

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  Like all globular proteins, enzyme molecules are coiled into a precise three dimensional shape, with hydrophilic R groups (side chains) on the outside of the molecule ensuring that they are soluble.
• Enzyme molecules also have a special feature in that they possess an active site. ​

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  The active site of an enzyme is a region, usually a cleft or depression, to which another molecule or molecules can bind. ​

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  This molecule is the substrate of the enzyme
• • Enzymes are very specific this is because enzymes have a particular shape into which substrates can fit.​

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  • The shape of the active site and substrate are complementary and this  allows the substrate to fit perfectly. ​
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  • The idea that the enzyme has a particular shape into which the substrate fits exactly is known as the lock and key hypothesis. 
• temperature

  The enzyme molecule begins to lose its shape and activity, and is said to be denatured. This is often irreversible. ​

  At first, the substrate molecule fits less well into the active site of the enzyme, so the rate of the reaction begins to slow down. ​

  Eventually the substrate no longer fits at all, or can no longer be held in the correct position for the reaction to occur.​
• Enzymes have an optimum pH at which they work fastest. ​

  For most enzymes this is about pH 7-8 (physiological pH of most cells), but a few enzymes can work at extreme pH, such as protease enzymes in animal stomachs, which have an optimum of pH 1.