Enzymes and the catalase lab
You’ve had most of this material;
today’s info is partly review.
PowerPoint is online
(paraphrase what’s new or important to you)
Enzymes and chemical reactions
 Chemical reaction:

One or more chemicals (reactants) react to form
different chemicals (products)
Reactant(s)

Product(s)
 Enzymes speed up chemical reactions in
cells/organisms

Often millions of time faster!
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
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Speed up = “catalyze”
(** careful** catalyze is not catalase)
ENZYMES ARE ONE TYPE OF PROTEIN
How enzymes work
 Enzymes provide a site for chemicals to come
together to react – like a “lock and key”
 Enzymes are specific – only help one or a few
specific chemicals react
 Enzymes may break down molecules (e.g. food)
 Enzymes may synthesize molecules (e.g.
building new proteins) (Animation)
What affects enzyme reaction rates?
 What affects enzyme speed?
 How much are produced by cells (more = faster)
 Mixing (more = faster)
 Temperature (warmer often = faster*)
 pH (the effect varies; most enzymes work well in a
narrow range, though this is variable)
 If conditions become unfavorable (too hot, too acidic,
etc), enzyme becomes “denatured”
 Denatured protein – tertiary structure becomes
permanently altered, making protein not work
 The “lock” and “key” no longer fit together
 http://www.biotopics.co.uk/other/anenz.html
Enzyme examples
 You may use these in your introduction…
 Rennin

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Produced by cow stomach lining
Used to curdle milk to make cheese
 Papain
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Present in papayas
Breaks down proteins in meat (meat
tenderizer), some venoms
 Amylase

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In saliva
Breaks down starch – into glucose
More examples…
 Cellulase

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In bacteria and fungi, mostly
Can be used to make ethanol from corn, sugar
 Catalase (the focus of our upcoming lab)

(** careful** catalyze is not catalase)
Catalase Lab!
 Catalase is an enzyme (“-ase” = enzyme)
 Present in your liver cells (and cells of many
other organisms)
 Breaks down hydrogen peroxide (a toxic cell
waste product) into water and oxygen

2H2O2  2H2O + O2
 One catalase molecule

Breaks down 40 million H2O2 molecules per
second!
 Remember the demo.
Catalase lab
 Each lab group:
Design, conduct an experiment
 How does (choose a variable) affect the rate of
the catalase and hydrogen peroxide reaction?
 Note: for the type of catalase we’ll use, we’ll
consider 20 degrees C to be “normal”
 Choose from these possible variables to test:
 Heat (Increasing temp)
 Cold (Decreasing temp)
 pH (increased or decrease pH)
 Catalase concentration (more dilute)
 Something else?

Catalase lab
 Each student:
Introduction due Monday
 Typed is best, handwritten is ok
 Just question, hypothesis, background info
 Nothing about the procedure, yet
 Entire lab report due later…
 Review rubric now…
 I’ll explain procedure Monday.
 Each lab group:
 Time to discuss MV, hypothesis, introduction
 RECORD ON PAPER TO BE TURNED IN:
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M.V., questions about intro/lab