Bio H - Biochem
Enzyme Note Packet
Enzymes are a type of _____________________ meaning they are a folded chain of _______________________.
In living things they act as _________________________________ which means: _______________________________
__________________________________________________________________________________________________
__________________________________________________________________________________________________
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Enzymes are NEITHER reactants of a reaction NOR are they products. They are “Matchmakers” so to speak…
o For this reason we write the name of the enzyme ABOVE the chemical reaction arrow, not to the right or
left (draw below)
While we will eat enzymes from other organisms, like all proteins, we do not use them directly. Instead we___________
__________________________________________________________________________________________________
Enzymes are needed for ALL chemical reactions that happen in the body including our two favorites
__________________________________ and ___________________________________.
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What’s the “chicken or the egg” question this brings up????
How do enzymes work:
Enzymes help provide the “right setting” for a chemical reaction. This means: __________________________________
__________________________________________________________________________________________________
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Remember when I made you hold the glucose models in a certain position to do dehydration synthesis?? (O in the
upper right corner). I was essentially telling you to “act like an enzyme” and make sure you molecules were
positioned correctly so the parts that react were next to each other.
By making it easier for substrates to react, enzymes lower the Activation energy of the chemical reaction
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Activation energy: The amount of energy needed to convert reactants into products
o
o
think of it as the “energy cost” of the reaction
the enzyme is a “coupon”
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Bio H - Biochem
Progression of the reaction
Some chemical reactions are spontaneous, and require no additional energy. But many require at least a small amount
of activation energy. Chemical reactions release energy which means that the _________________________ have
more energy than ________________________. These are called _______________________________________
reactions.
Other chemical reactions require energy input in addition to activation energy. In these reactions the
_______________________________ have more energy than the __________________________________. These are
called ____________________________ reactions.
Which is shown above? ____________________________
Draw an energy plot for the other type of reaction in the space next to the diagram above.
Enzyme reaction drawing:
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Bio H - Biochem
Catabolism (digestion)
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Anabolism (synthesis)
The last two diagrams are two examples of how an enzyme can be used.
o All “building” reactions that happen in your body fall under the heading of ANABOLISM.

o
___________________________________ is our favorite example of an anabolic reaction.
All “breakdown” reactions that happen in our body fall under the heading of CATABOLISM.

___________________________________ is our favorite example of a catabolic reaction.
The slides show the Catalytic Cycle of Sucrase
Step 1: Available substrate (sucrose) and enzyme (sucrase)
Step 2: Substrate binds to the enzyme . This is called an ________________________________________
Step 3: Substrate is converted to product: This means that sucrose has been ________________________ to form (st 4)
Step 4: Released products
_____________________ and ___________________ as well as freeing up the enzyme to
catalyze another reaction.
Enzymes have very particular tastes!
Enzymes are specific – each substrate that reacts in the body requires a different enzyme
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_______________________________________________________________________________________________
_______________________________________________________________________________________________
There are two theories on how this works:
1.
Lock and key: ___________________________________________________________________________________
_______________________________________________________________________________________________
Induced fit: _____________________________________________________________________________________
______________________________________________________________________________________________
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We now feel that induced fit is a more accurate model of what is actually happening.
How an enzyme works (or if it works) depends on the ___________________ ___________________ If this
location is changed or damaged (a mutation in the DNA  an incorrect amino acid) the enzyme may not function
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Bio H - Biochem
properly and a reaction cannot be catalyzed.
Not only are enzymes picky about what substrates they work with, but also the following conditions:
1.
Each enzyme has an optimal temperature. Explain this
statement using the graph below:
2. Each enzyme has an optimal pH.
a. pH is? ______________________________________________________________________________
b. changing the concentration of H+ interferes with the bonds holding the protein in its folded shape.
Explain the graph below. Is the optimum pH always around 7? Explain
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Bio H - Biochem
DENATURATION
BOTH temperature and pH will change the 3D
shape of the protein, usually unfolding it.
Denaturation: the process of unfolding the 3D
shape of a protein. DOES not disrupt the
primary structure.
MAY be reversible if conditions are returned to
optimal levels. Prevents the enzyme from
working. NO product will form
Effect of substrate concentration and/or enzyme concentration
What is it telling us?
What would happen if the amount of substrate were
constand and you increased the amount of enzyme?
Some enzymes need “helper” molecules
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Coenzyme: organic molecules (like vitamins) that help a substrate bind to its enzyme
Cofactors: inorganic molecules (like Zn, Cu) that help a substrate bind to its enzyme
Both attach coenzymes and cofactors bind to the enzyme and improve chances that the substrate will bind.
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Bio H - Biochem
Label the parts of this diagram
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Bio H - Biochem
Inhibiting an enzyme
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Inhibit: shut down or suppress
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Can be caused by outside molecule – drugs/poisons
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Can be caused by inside molecule if your body wants to temporarily shut down a reaction
–
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Why waste the energy if you don’t need the product right now?
Competitive Inhibition– molecules that are similar in shape to the substrate bind to the active site and block the
substrate; No chemical reaction can happen
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Examples:
Sulfa drugs mimic PABA a chemical essential in bacterial biochemical pathways
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Non-competitive Inhibition– molecule different from the substrate binds to a part of the enzyme other than the
active site and alters the shape of the active site; No chemical reaction
– Examples:
Nerve gas permanently blocks nerve transmission
Penicillan permanently blocks the assembly pathways for certain bacteria
How are competitive and non-competitive inhibition different?
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