Click on the Link below to take you to the website.
http://www.phschool.com/science/biology_place/labbench/lab2/concepts.html
A) Three Key Concepts
1) Enzymes catalyze reactions by lowering the activation energy necessary for
a reaction to occur. The molecule that an enzyme acts on is called the
substrate.
Click on the blue words above and provide a definition of each one.
Enzyme:
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Activation Energy:
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Substrate:
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2) In an enzyme-mediated reaction, substrate molecules are ____________,
and ____________ is ____________. The enzyme molecule is
________________ after the reaction, and it can continue to catalyze the
same type of reaction ____________ and _____________.
3) Each enzyme is ________________ for the reaction it will catalyze and
the enzyme is not “used up” in the reaction.
catalase
hydrogen peroxide
water + oxygen gas + catalase
Substrate = hydrogen peroxide (H2O2)
Enzyme = catalase
Products = water and oxygen
B) Enzyme Structure
Enzymes are globular proteins. Their folded conformation creates an area
known as the active site. The nature and arrangement of amino acids in the
active site make it specific for only __________ type of substrate.
Define  Active Site:
____________________________________________________________
____________________________________________________________
C) Binding Specificity
Even when __________________ substrate molecules are present, only those
that have the specific ____________ complementary to the active site are able
to bind with the enzyme's active site.
http://www.phschool.com/science/biology_place/labbench/lab2/binding.html
D) Induced Fit
When an enzyme binds to the appropriate substrate, subtle ____________ in the
active site occur. This alteration of the active site is known as an induced fit.
Induced fit ____________________ catalysis, as the enzyme converts
substrate to product.
Define  Induced Fit:
______________________________________________________________
______________________________________________________________
http://www.phschool.com/science/biology_place/labbench/lab2/induced.html
Release of the products _______________ the enzyme to its ____________
form. The enzyme can ____________ this reaction over and over, as long as
________________ molecules are present.
E) Some Factors That Affect Enzyme Action
The ________________ of an enzyme is maintained by interactions between the
various amino acids that compose it, and this conformation is sensitive to changes
in the enzyme's ________________. Two important influences are _______ and
____________________. When an enzyme's conformation is significantly
____________________ because of pH or temperature variation, the enzyme
may _____ _______________ catalyze reactions. An enzyme is said to be
_________________ when it loses its functional _______________.
F) pH and Enzyme Function
Each enzyme functions best within a ________________ pH range. For example,
the enzyme _________________, which works in your ______________,
functions best in a strongly _______________ environment. _____________, an
enzyme found in your small __________________, works best in a
_______________ environment.
When the pH ______________, the active site progressively _______________
and ______________ enzyme ________________. What happens to catalysis
when an enzyme is subjected to a pH far from its optimum range?
http://www.phschool.com/science/biology_place/labbench/lab2/ph.html
In the presence of either excess H+ or excess OH- ions, the globular protein's
_______________ is ______________. The active site is ____________ and
the enzyme ________________ catalyze reactions.
G) Temperature and Enzyme Function
Chemical reactions ___________ _______ as temperature is
_______________, so, in general, catalysis will increase at higher temperatures.
However, each enzyme has a temperature ____________, and beyond this point
the enzyme's functional __________ is _____________. _________________
temperatures will _______________ most enzymes.
Now you are ready to proceed with the experiment that we will do in class. Not the
one in this animation.
Substances
Reaction Rate Before
Heating
Reaction Rate After
Heating
Potato
Potato
Catalyst Reaction
H 2O 2
&
MnO2
Enzyme Reaction
H 2O 2
&
catalase
Liver
Liver
H) Enzymes Important to Living Things Because…
Without enzymes, reactions in living things would be _______ _________,
but when a reaction is assisted by an enzyme the rate (speed) of the reaction is
_____________.
rate of product formation
Vmax
Enzymatic reaction
Fast reaction rate
Vmax/2
Non catalyzed reaction
Km
Slow reaction rate
[conc. of substrate]
Without enzymes, reactions in living things would have to occur at such
____________ temperatures that ____________ tissue would be
________________. Enzymes ______________ the activation energy of
reactions allowing them to occur at ____________ temperature. Activation
energy is the amount of ______________ that is needed to get a reaction
______________. It is seen as a ____________ in an energy profile between
reactants and products that must be ______________ before the reaction
Temperature
proceeds.
I)Competitive Inhibition
Competitive inhibition refers to a _________________ for the _________
_________ of the enzyme by an ______________ agent (poison) called a
____________________.The nonsubstrate’s shape ______________ the
proper substrate’s shape, but when the nonsubstrate and the enzyme join ____
______________ occurs. _____________, a component of _______________
smoke, is a competitive inhibitor of an enzyme in the ____________. When it
attaches to the enzyme it ____________ the use of oxygen by the cell, causing
the cell to _______________.
J) Coenzymes
Coenzymes are substances that __________________ to help an enzyme and its
substrate ________ together _____________. ____________ and
________________often act as coenzymes.
Why is it important to make sure that you get sufficient amounts of vitamins and
minerals in your daily diet? Don’t just write down statement, you must expand upon
it.
______________________________________________________________
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K) Catabolic and Anabolic Reactions
Catabolic reactions occur when a molecule is ___________ ____________ by an
enzyme. These reactions are __________________ and provide body
___________ to the organism.
Anabolic reactions occur when _____________ molecules are ___________
_______________, by an enzyme, to form one _____________ molecule. These
reactions are _____________ and occur in warm blooded animals during
__________ or after they have _____________.
L) Metabolism
Metabolism is the ________ of all of your body’s ______________ and
______________ reactions, otherwise known as your _________________
__________________.
M) How Enzymes Are Named
The name of an enzyme usually ends in “_________” and ______________ the
name of the ________________ that it acts upon.
Complete the following chart. “Lipid” is done for you.
Substance
sucrose
lactose
H 2O 2
maltose
lipid
cellulose
Enzyme
Subunit
Subunit
lipase
fatty acid chain
fatty acid chain
N) Lock and Key Analogy
The “lock & key” analogy is commonly used to explain how an enzyme knows exactly
which substrate it should bind to. Use the pictures below to help you to explain
how a lock with its key is very similar to an enzyme with its substrate. Discuss this
question with someone then formulate an answer and write it in the space below.
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If enzymes do not get used up in the reactions they assist would it be possible for
a lactose intolerant person to drink a glass of regular milk if it had first been
mixed with some Lactaid milk?
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