Tuesday November 3rd - Catalase Lab

Tuesday we actually had a chance to see the action of an enzyme.  You entered the class to an interesting site for sure!!

I first gave a little introduction to Catalase.  Catalase is an enyzyme found in nearly all living organisms.  Its role is to break down Hydrogen peroxide (a natural by-product of certain metabolic reactions) into less harmful substances.

First thing we did was write the reaction down (on your lab note card)

This tells us that with the enzyme catalase - for every two hydrogen peroxide molecules, 2 water molecules and one molecular (gaseous) oxygen is produced.

Soooooo - We added Hydrogen peroxide to chicken livers.  (While all cells contain catalase, liver tissue has a a high concentration of catalase)

This is what happened:

Bubbles galore!!   Watch the following video to see what happened and hear our discussion.

Next up... lets see if in fact what was left was just water:
On your cards:

And............. this is what happened:

While we can't make a definitive conclusion that what was left was water - Knowing the reaction and products we can safely assume that the liquid that was left was NOT hydrogen peroxide (or it would have bubbled)

Next was to test to see if enzymes were reusable:

On your Cards:

We took the ORIGINAL piece of liver (that already degraded hydrogen peroxide) and added MORE hydrogen peroxide.  If the enzymes had been used up, we would expect no reaction to occur.  If they were NOT used up.... then the same thing should happen!!

And that is exactly what we saw - BUBBLES GALORE!!!

Next was to test the effect of pH on enzyme activity.  We added Vinegar (an acid) to our liver, let it sit and soak into the liver, then added hydrogen peroxide AGAIN.

Our note card:

AND.....  NOTHING happened.  SOME of you had a very small reaction, but nobody had a full blown bubble fest like you did the first time.  What does this tell us about the effect of pH on enzymes????!?!?!  Did the enzymes "die".. NO (they aren't alive.) Did the enzymes disappear??? NO - they are still there - we already saw earlier that they are reusable.  SOOOOOOOOO  - what could explain no reaction???

THE ENZYMES SHAPE changed (specifically the active site) and therefore they were denatured!!!

We will use our observation cards to do a detailed analysis of this on Thursday!!!