OCR AS Biology - Enzymes

Enzymes and Temperature
1. How and why temperature affects enzyme
  1. As an enzyme is a protein, if the tertiary structure of an enzyme is changed significantly it can't function, this isn't reversible and the tertiary structure is too damage to rebuild and this is called denaturation.
  2. Having a higher temperature will increase the rate of which the molecules move, resulting in the molecules gaining more kinetic energy resulting in the molecules colliding more often and if the kinetic energy of both enzyme molecules and substrate molecules is increased, there will be an increased number of collisions
What are they?
1. Function
  1. Enzymes make reactions go faster in digestive and metabolic processes. They are called 'catalysts' because they speed up the reaction by lowering the amount of energy needed to get the reaction started.
2. The Enzyme is the blue protein and the substrate is the purple molecule and when these fit together at the active site it makes a enzyme substrate complex
3. Enzyme induced fit hypothesis
  1. When a substrate molecule collides with an enzyme, if its composition is specifically correct, the shape of the enzyme's Active Site will change so that the substrate fits into it and an Enzyme-Substrate Complex can form. This produced a product called a enzyme product complex. The product is a different shape from the substrate so it can no longer fit in the active site so it moves away. The enzyme is now able to catalyse the same reaction with another substrate molecule
Enzymes and pH
1. Enzymes have different optimum pH. At optimum pH the concentration of hydrogen ions in solution gives the tertiary structure of the enzyme the best overall shape, and this shape holds the active site in the shape that best fits the substrate
2. Enzymes usually work in a fairly narrow pH range. Changes to pH, could result in a fall of reaction rate because the shape of the enzyme molecule is disrupted so the shape of the active site is changed, even if the change is slight.
3. The optimum pH for an enzyme depends on where it normally works. For example, intestinal enzymes have an optimum pH of about 7.5. Enzymes in the stomach have an optimum pH of about 2.
Enymes and concentration
1. Enzyme Concentration
  1. As the enzyme concentration increases,more active sites become available
    1. More enzyme substrate complexes form
      1. If the enzyme concentration increases further, a point will be reached where all substrate molecules are occupying enzyme active sites.
2. Substrate Concentration
  1. As the substrate concentration increases, collisions increase, so more enzyme substrate complexes form,so more products are formed.
    1. If the concentration increases further, a point will be reached where the reaction rate reaches a maximum value.

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OCR AS Biology - Enzymes

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