Enzymes

Learning objectives

• • define an enzyme
  • explain the properties of enzymes
  • explain enzyme action
  • investigate factors that affect the rate of enzyme catalyzed reactions

• enzymes are proteins that act as biological catalysts
• catalyst is a molecule that speeds up a chemical reaction, but it remains chemically unchanged

 

Examples of enzymes

• pepsin,
• salivary amylase,
• trypsin etc

 

Enzyme Specifity

• they are specific
• this can be demonstrated by the lock and key hypothesis
• specific shape can fit into a complementary key

 

Metabolism

• all reaction needed in order stay alive
• can be catabolic reactions, breaking down reactions.
• or can anabolic reaction ie build up reactions

 

Characteristics Of Enzymes

• they are proteins
• they alter or speed up the rates of chemical reactions they catalyze
• they remain unchanged after the chemical reaction
• they are specific- catalyze only one type of reaction eg amylose act on starch to produce sugar
• they are affected by temperature, pH etc

 

Factors Affecting Enzyme Activity

Temperature

 

• The enzyme activity is increasing as the temperature increases as the molecules gain k energy.
• The enzyme works best at its optimal temperature
• The enzyme activity decreases at temperature above the optimal temperature, at extreme temperature, the enzyme stopped as they are denatured

 

pH

• The enzyme activity is increases from its inactive state as the pH (acidity/alkalinity) increases
• The enzyme is at its most active state at optimum/optimal pH (optimum acidity/optimum alkalinity)
• Most enzymes work best at neutral pH, some enzymes work best at acidic pH and some enzymes work best at alkaline pH
• eg pepsin is found in the stamach which is acidic and trypsin si found in the duodenum where the medium is alkaline
• The enzyme activity decreases
• when it is exposed to above the optimal pH, the enzyme stopped because they are denatured.

 

Enzyme Inhibitor

• An enzyme inhibitor is a substance that binds to the enzyme and decreases its activity.
• The presence of these inhibitors decreases the enzyme activity and so the rate of reaction.
• There are two types of inhibitors

 

1. competitive inhibitor

• Competitive inhibitors are inhibitors that bind at the enzyme’s active site.
• They compete with substrates for the active site.

 

2. Non-competitive inhibitor

• Non-competitive inhibitors are inhibitors that bind at a site other than the enzyme’s active site.
• When they bind to the enzyme the shape of the active site is changed.

 

Industrial application of enzymes

1. Biological washing powder

•  Biological washing powder contains many enzymes such as lipase and protease which remove
  fats, grease and protein stains from the fabrics.
• When the washing powder is soaked in water with fabrics, enzymes break down stains into
  soluble molecules which can be washed away easily.
• This is why biological washing powders are effective at removing hard stains like grease or
  bloodstains from fabrics.

2. Beer formation

• Beer is formed by fermenting sugar using yeast.
• Amylase, an enzyme, is used to break down starch into simpler sugars that can be usable by
  yeast.

3. Cheese making

•  Enzymes play an essential role in cheese making.
•  Rennet enzyme is used.
• This enzyme contains rennin and pepsin that coagulate milk to curd.

 

4. Baking

• Amylase is used in the baking industry.
•  This enzyme breaks down starch into simpler sugars on which yeast can work upon