REFLECTION 16: FACTORS AFFECTING REACTION VELOCITY

Hey fellow biochemians! Still under the enzymes topic, today we will be looking at the factors that affect reaction velocity. In class we said that there were four factors affecting reaction velocity:

1.      Substrate Concentration

2.      Enzyme Concentration

3.      Temperature

4.      pH

Today we will be focusing on how temperature can affect the rate of an enzyme catalyzed reaction. Let us get right into it!

As you increase the temperature you are increasing the energy of the system thus increasing the rate of reaction. Why is this you may ask?

Well there are two factors that contribute to this statement:

1.      By increasing the temperature of the system you are also increasing the collision frequency between the substrate molecules and the active site.

2.      Secondly, by increasing the temperature of the system you are also increasing the amount of substrate molecules that will have enough energy to overcome the activation energy hence a faster rate of reaction.

So we can say that the more collisions the more enzyme-substrate complexes forming and eventually more products being formed. Now this is good for a reaction; however, yes folk there is a twist, as the temperature increases beyond the optimum temperature the rate of reaction quickly plummets. This is because as the temperature increases the ionic and hydrogen bonds weaken and start to break. A further increase in temperature leads to more bonds being broken and the enzyme’s tertiary structure being changed thus leading to a change in the shape of the enzyme’s active site. Because the enzyme’s active site is complementary to the substrate, once the active site’s shape changes the substrate can no longer bind to the enzyme thus decreasing the rate of reaction.  Eventually the whole tertiary structure will unravel and the enzyme will stop working. When this occurs we can say that the enzyme has been denatured. Denaturation refers to the alteration of a protein’s shape by the lost of its tertiary structure from some external source such as heat. We say denaturation is a cooperative process.

Lastly, let’s look at the graph for this particular question.

enzyme_activity

As you can see this graph is non-symmetrical because denaturation takes place very quickly. The optimum temperature for most human enzymes is 37-40 C, temperatures higher than this in most cases will lead to denaturation. 

This can be a really good answer for an exam question, so I hope it is useful to you guys in some way. Thank you for your time.

References

http://www.sciencedaily.com/articles/d/denaturation_(biochemistry).htm

Youtube:  BiochemJM

Featured Image: http://www.bbc.co.uk/schools/gcsebitesize/science/add_ocr_pre_2011/homeostasis/importancerev4.shtml

Image- http://soniasrevisionblog.wordpress.com/2013/02/21/enzymes-and-the-effect-of-temperature-on-enzyme-activity/

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