What is an Enzyme?

• Enzymes are biological catalysts that speed up chemical reactions happening in cells, without itself being used up.

• Enzymes are usually protein molecules.
• Enzymes are very important to life because they are involved in important functions of the body, such as digestion.

How do Enzymes Work?

• Enzymes bind to one or more reactant molecules, which are called substrates. 
• The site where the substrate binds is called the enzyme's active site.
• The shape of the active site matches the shape of the substrate. Therefore, enzymes are very specific, which means that one type of enzyme can only speed up one type of reaction.
• After the substrate binds to the enzyme, the enzyme can help to break up the substrate into many smaller molecules or to bind many substrates into a bigger molecule.
• If the shape of the enzyme changes, the substrate will no longer be able to bind to the enzyme, and the enzyme will no longer be able to modify the substrate. When this happens, we say that the enzyme is denatured. 
  • High temperature or extreme pH can cause an enzyme to become denatured.

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Effect of Temperature on Enzyme Activity

• Enzymes function best at 37°C, which is around the body temperature. We say that 37°C is the optimum temperature for enzyme activity.
• Below 37°C, the enzyme activity increases as temperature increases.
• However, above 37°C, the enzyme activity decreases rapidly because the enzymes get denatured.

Effect of pH on Enzyme Activity

• Each type of enzyme has different optimal pH. 
  • For example, the optimum pH of pepsin is 2.4 since pepsin functions at an acidic environment in the stomach.
  • The optimum pH of trypsin is 8 because trypsin functions at a slightly alkaline environment in the small intestine.
• Outside of their optimal pH, enzymes become denatured and have decreased enzyme activities.

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