Wednesday October 1st - Enzyme activity and Effect of Temperature

Today we only had one daily question and it was used to prepare us to today's activity:

Then we started into probably the GROSSEST lab of the year!!
The room stunk a little when you came in here today because of THIS......

We worked with fresh chicken liver today to look at the enzyme called catalase.  As the daily question mentioned, catalase is an important enzyme found in all living tissue that aids the the breakdown of hydrogen peroxide into water and oxygen.  We use liver tissue because liver has a VERY high concentration of catalase in it compared to other tissue. 

To see the reaction that was mentioned in the daily question we added hydrogen peroxide to a test tube then added a piece of the liver:

As the reaction continued
 the amount of oxygen
released increased the
amount of water
that accumulate
also increased.

As soon as the liver hit the
hydrogen peroxide
the reaction began.
The bubbles indicated that
Oxygen (O2) was being release
The resulting liquid would
 then be water.

To show that what was left in the tube was simply water and no longer hydrogen peroxide, we moved the liquid from the completed reaction into another tube.  If, in fact, that liquid was ONLY water and NO peroxide then adding a fresh piece of liver would not end in a reaction.

As you can see this was the liquid left - which we hypothesized was only water (and some liver juice).  When dropping a new piece of liver into the liquid, no reaction occurred.

Next up we wanted to test if the catalase found in the liver is REUSABLE........  So using the SAME piece of liver that we worked with first (that already completed on reaction) we added MORE hydrogen peroxide.

And Viola - You can see the tube on the left, that had the original liver was performing the reaction just as well as when the liver was fresh!!

We then moved on to notes about the effect of TEMPERATURE on enzyme action:

While you were writing these notes down I had the liver in some water and heated it to boiling.  At that point I added hydrogen peroxide and NO reaction occurred.  If you look at the graph above, it describes what happens to Enzymes that are heated past their "optimum temperature" the enzymes are Denatured.  This means the SHAPE of the enzyme has changed.  Remember we talked about how changing the shape of ANY protein will alter the function of it.  In enzymes specifically this is even more important because enzymes have a specific active site where the reactant(s) bind and if that is changed, the enzyme can no longer aid in that reaction.