3.6: Enzymes

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  1. Define an enzymes and its active site.
    An enzyme is an organic catalyst that changes the rate of the reaction without being consumed by the reaction. Enzymes are globular proteins. The active site is the part of the enzyme that attaches to the substrate with weak chemical bonds.
  2. Explain how enzyme-substrate specificity assists the reaction between molecule A and molecule B
    The enzyme and substrate model is often called a 'lock-and-key' model. The diagram shows how molecule A and molecule B fit into the enzyme and are bound at their respective active sites. This means that the reaction between A and B can proceed more quickly as contact does not depend upon random collision.
  3. Explain how temperature affects enzyme activity.
    Increased temperature increases enzyme activity until the optimum temperature. Different enzymes have different optimal temperatures. If the temperature continues to rise above the optimal temperature, the enzyme denatures, or becomes inactive and can no longer bind with the substrate.
  4. Explain how pH affects enzyme activity.
    Every enzyme has an optimal pH, e.g. pepsin in the human stomach works best at approximately pH = 2, while trypsin in the small intestine works best at approximately pH = 8.
  5. Explain how substrate concentration affects enzyme activity.
    The rate of reaction will increase with an increase in substrate concentration until it reaches a point when all enzymes molecules are actively involved in the reaction. At this point other limiting factors become important and the rate levels off.
  6. Define denaturation.
    Denaturation is a change in the structure of the molecule so that it can no longer perform its normal functions.
  7. What is lactose intolerance?
    Lactose intolerance is a condition in which a person has lost the ability to produce lactase and will have a reaction, e.g. diarrhoea if they consume a lactose-containing food.
  8. Explain how lactase has been used to assist people with lactose intolerance.
    The enzyme lactase has been attached to a large molecule and brought into contact with the food, e.g. milk containing lactose. The lactase breaks the lactose down into glucose and galactose. People with lactose intolerance do not suffer the same effects. If they consume glucose or galactose and thus can consume milk, cheese, ice cream and other dairy products.
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3.6: Enzymes
3.6: Enzymes
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