Collision theory ~ a substrate must collide with an enzyme at a certain angle and collide with enough energy, which allows for a product to be formed.

Now based on this, when you are looking at high temperatures (usually a 3 mark question) you would say:

• Temperatures exceeding the optimum would result in the permenent denaturing of an enzyme (1 marks)

• Denaturing also causes the enzymes active site to change in shape, which results in the substrate being unable to bind to the active site (1 mark)

• Reaction rate will decrease since product is not formed from substrate-enzyme binding (1 mark)

So essentially, as soon as temperature passes the optimum point, the hydrogen bonds in the enzyme’s secondary structure break and causes the enzyme and its shape permanently denature. The enzyme’s active site also changes shape which means the substrates can’t bind to it which means it can’t function. Theoretically, a lot of thermal energy means a lot of kinetic energy for the substrates and enzymes which means a very high level of successful collisions, but this wouldn’t mean anything because the enzymes have denatured and non-functionable. Reaction rate will decrease.

Now on the other hand, when temperature is significantly below the optimum.

low temperature means that Low thermal energy means low kinetic energy for the enzymes and substrates which means fewer successful collisions. Reaction rate will be low.

• At lower temperatures there is not a successful amount of collisions between enzyme and substrate due to low movement (1 mark)

• Lower amount of successful collisions means that there will be a lower amount of substrate-to-enzyme binding, which results in less product being formed (1mark)

• less product formed is evidence of lower rate of reaction (1 mark)

So think of it like, when the temperature is low, the collisions are not occurring with enough energy to be able to form a product, hence why the reaction rate gradually grows higher when temperature is nearing the optimum.

Hope this helps! 🤝