This document discusses the enzyme catalase and an experiment testing its activity. It begins by outlining the learning objectives, which are to understand the household use of hydrogen peroxide, recognize enzyme characteristics, and explain how temperature and pH affect enzyme activity. It then provides background on enzymes as biological catalysts and proteins that speed chemical reactions. The experiment tests how quickly catalase breaks down hydrogen peroxide into oxygen and water, and how this reaction rate is impacted by different temperatures and pH levels. Factors like temperature and pH are outlined as things that can change an enzyme's structure and alter its function.

1. Lab 4 - Enzymes &
The Catalase Lab
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2. After completing this activity,
students will be able to:
• Determine the household use of Hydrogen
Peroxide
• Recognize different enzymes and their
characteristics
• Compare and contrast the catalase in animal
vs. plant cells
• Explain why temperature and pH would have
an effect on enzyme activity
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3. What are Enzymes?
• Enzymes are Biological Catalysts - substances
that increase the speed of chemical reactions.
• When an enzyme is present it takes less energy
to start a chemical reaction (activation energy)
• Enzymes help maintain homeostasis
• Enzymes facilitate metabolism – which is
essential for life
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4. • Enzymes are
proteins.
• Proteins are made
up of amino acids
• Enzymes work with
a very specific
substrate (the
molecule acted on
by an enzyme) to
speed up a reaction
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5. • Enzymes have one or more deep folds on its
surface
• These folds form pockets called active sites
• Enzymes act on the substrate, by fitting into
the active site like a puzzle
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6. Enzymes and their substrates
• Each enzyme has a definite
3-D shape that allows it to
bind with its substrate
• Each enzymes acts only on
one specific substrate,
which means they break
down specific substances
(like a lock and key)
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7. Why do we need enzymes?
• Enzymes work to:
– Turn leaves colors in the fall (think of the yellows,
oranges, reds, purples)
– Ripen foods (this is what makes your bananas
brown, or apples get mushy),
– Digest foods after they are eaten,
– Produce DNA and hormones
• Without enzymes, life as we know it is not
possible
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8. What affects enzymes in a reaction?
• Temperature
• pH
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9. Temperature
• There is one temperature
at which specific enzymes
work best.
• This optimal temperature
is usually around human
body temperature (37.5
oC) for the enzymes in
human cells.
• Above this temperature
the enzyme structure
begins to break down
(denature) (ie. fever)
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10. pH
• Enzymes have an
optimal pH. However
the optimum is not the
same for each enzyme.
• Enzymes are found at
different places in your
body, and in the
environment
• pH would be different in
the body vs. stomach
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11. Factors that affect enzyme activity
• Temperature
• Low temperature (cold) = reactions occur slowly
• High temperature (hot) = enzymes denature, which can change the
structure of proteins and alter the enzyme’s function forever
• pH
• pH scale goes from 0-14
• pH of pure water is 7
• Basic (pH higher than 7); Acidic (pH lower that 7)
• Changes in pH can also change the structure of proteins and alter
the enzyme’s function.
• Organisms can only tolerate (stand) small changes in pH because
every cell has a particular pH at which it functions best
(homeostasis).
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12. Examples of Enzymes and their
Substrates
Enzyme Substrate
Amylase---------------------Starch
Maltase----------------------Maltose
Sucrase----------------------Sucrose
Lipase------------------------Lipids (Fats)
Pepsin------------------------Proteins
Catalase--------------Hydrogen Peroxide
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13. Catalase
• 2H202
 2H20 + 02 (gas)
• The products of the above reaction are
oxygen gas and water, two non-poisonous
molecules. In living cells, the oxygen can be
used for cellular respiration and the water can
be excreted.
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14. H2O2 is similar to H2O
• Hydrogen peroxide is chemically very similar to
water.
• Water = H2O,
• Hydrogen peroxide = H2O2.
• In chemistry, things can change a lot when you
change the formula.
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15. • An extra atom of oxygen also makes hydrogen
peroxide a very different chemical, which can
be dangerous if it is concentrated.
• That is why the H2O2 you get at the grocery is
only 3%. The rest is plain water and it is
diluted enough to make it safe for household
use.
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16. Scientific Terminology (used in this lab)
• Control – the constant between experimental
groups
• Independent variable – the one variable that
changes between experimental groups
• Dependent variable – measured variable
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17. POST LAB
• What causes the bubbles?
• Why did some substances bubble more than
others?
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