Biology 2.7 Factors Affecting Enzyme Action

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…