Effect of Temperature on Enzyme Activity

Instructor: Sarah Phenix
In this lesson we will explore what an enzyme is, how an enzyme functions and then explore in what way temperature may affect the activity of an enzyme.

What are Enzymes?

All enzymes are proteins, meaning they are molecules composed of one or more large chains of amino acids joined by peptide bonds. Now, the job of an enzyme is pretty important, it catalyzes, or speeds up, chemical reactions by reducing the amount of energy needed for that reaction to take place. You could think of enzymes almost like a flash sale in that enzymes temporarily 'discount' the energetic cost of the reaction.

Example Rendering of Enzymatic Shape
Example Rendering of Enzymatic Shape

What's also important to note it that enzymes aren't consumed nor are they changed by the chemical reaction- they can leave one reaction and move on to instigate another. Enzymatic reactions occur when target substance, called substrates (the specific substance that will undergo change), binds with the active site on the enzyme. Active sites work like a lock and key in that each active site is specific to a particular 'key', or substrate. Now, once that substrate binds with an enzymes's active site it becomes an enzyme/substrate complex. This union of enzyme and substrate creates an energy change resulting in the substrate splitting into smaller molecules (becoming an enzyme/product complex). Finally, with its job complete, the enzyme releases the resulting smaller molecules, called products, back into the environment.

Enzymatic Activity
Enzymatic Activity

What is Temperature?

Ok, so this might sound strange but you can think of enzymes almost like people in that different people prefer different ambient temperatures, to the point that they might actually behave differently outside of that preferred temperature. For instance, if you're someone who gets cold easily then you might find yourself choosing to be less active in the winter in favor of curling up with a blanket. Conversely, someone with a different body composition may not be as sensitive to the cold and may in fact prefer colder temperatures than you do. Well, enzymes react in the exact same varied way.

Some enzymes, such as those used by the thermophilic (heat loving) bacteria found in hot springs, exist in an environment with a temperature ranging from 41-122 C (106-252 F), while those enzymes found within you or I function best at around 37 C (98.6 F), while still others, like those found in psychrotolerant (cold tolerant) bacteria, can happily function at 0 C (-32 F). So, as you can see, there is quite a range of environmental temperatures that enzymes can exist in and, just like you or I, these enzymes react differently outside of their 'preferred' temperature. So what does 'differently' mean? Well, that has to do with their rate of reaction and the amount of products they create. Just like you or I are more productive studying or doing homework when we aren't too cold or too hot, enzymes also have an optimal temperature where they produce the most product at the fastest rate.

How do Temperature and Enzymes Interact?

So, with the knowledge that the actual range of environmental temperatures could be anywhere from 0 C to 252 C (-32 to 252 F), I bet you could imagine that the particular temperature of the environment would affect the way in which a particular enzyme functions. Why is this? Well, enzymes, being proteins, gain their molecular shape based on the interactions between the amino acids that make up their long protein chains. Remember the last time you played with magnets and faced two positive sides or two negative sides together- they resisted each other, right? Well, that resistance occurs between the charges of atoms that compose molecules, too, and this affects the way the amino acids fold to take their shape.

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