Biology 2.7 Factors Affecting Enzyme Action

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For an enzyme to work it must:

  • have physical contact with its substrate.
  • have active site that fits substrate.

Measuring enzyme-catalysed reactions

To measure the progress of enzyme catalysed reactions, measure the time course (how long it takes an event to run its course). Events often measured:

  • Formation of products of reaction.
  • Disappearance of substrate.

Explanation for graph shapes:

  • Lot of substrate at first.
  • Easy for substrate to come into contact with active sites.
  • All active sites filled and substrate broken down quickly.
  • Amount of product increases as substrate decreases.
  • More difficult for substrate to come into contact with active sites - less substrate and products may get int the way.
  • Rate of substrate disappearance slows, graph tails off.
  • Rate of reaction continues to slow until concentration of substrate cannot be measured.
  • Graph flattens out as all substrate used so no new product produced.

Effect of temperature of enzyme action

NB: Rate always expressed per time unit.

Rise in temperature = more kinetic energy for molecules = molecules more more rapidly = collide with each other more often.

This means enzyme and substrate come together more often = rate of…


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