1_7_enzymes_
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biology enzymes slidesTRANSCRIPT
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UNIT 1: BIOCHEMISTRY 1.7 Enzymes
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Homework Questions?
10. Nucleotides Amino Acids
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Enzymes
Biological catalysts usually having names ending in
(-ase)
Involved in, but not changed by, a chemical reaction.
Proteins with a tertiary or quaternary structure
Commercial uses include: cheese, corn & bleach
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Many enzymes function by lowering the activation energy (Ea) of reactions. Temperatures within living things are relatively low. By lowering the activation energy required cells are able to carry out reactions by the use of enzymes
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Enzyme Action
The functioning of enzymes is determined by its shape
The arrangement of molecules on the enzyme produces an area known as the active site within which the specific substrate(s) will "fit (i.e-substrate specific) e.g- The enzyme peptidase (which breaks peptide bonds in proteins) will not do the same to starches (which are broken down by human-produced amylase in the mouth).
Substrates bind to active sites on enzymes, forming the enzyme-substrate complex
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Induced-Fit Model
Notice how enzyme alters its shape to better fit substrate!
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Example: Sucrase
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Special Considerations
Some enzymes require cofactors in order to function:
1) Cofactors: non-proteins essential for enzyme activity. Ions such as K+ and Ca+2 are cofactors.
2) Coenzymes: organic cofactors
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Factors Affecting Rate of Enzyme Activity
1) Temperature
Increases in temperature will speed up the rate of non-enzyme mediated reactions, and so temperature increase speeds up enzyme mediated reactions, but only to a point. When heated too much, enzymes (since they are proteins dependent on their shape) become denatured. When the temperature drops, the enzyme regains its shape
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2) pH
Enzymes are also adapted to operate at a specific pH or pH range. Any change in pH level will denature or change the shape of the enzyme.
Notice the optimal pH is different for
different enzymes!
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2) The concentration of substrate and product also control the rate of reaction, providing a biofeedback mechanism.
3) Inhibitors can lower the rate at which an enzyme catalyzes a reaction. There are both competitive and non-competitive inhibitors.
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Competitive Inhibition
Notice how the inhibitors
have the same shape
as the substrate!
They compete with the substrate for access to
the active site.
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Non-Competitive Inhibition
The inhibitory chemical, which does not have to resemble the substrate, binds to the enzyme other than at the active site. When the chemical either permanently binds to or massively denatures the enzyme so that the tertiary structure cannot be restored, the process is irreversible.
Many drugs and pesticides act in this way!
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The Biochemical Pathway
Enzymatic pathways form as a result of the common occurrence of a series of dependent chemical reactions
The end product depends on the successful completion of five reactions, each mediated by a specific enzyme.
The enzymes in a series can be located adjacent to each other (in an organelle or in the membrane of an organelle), thus speeding the reaction process.
http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120070/bio09.swf::A%20Biochemical%20Pathway
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Feedback Inhibition
Used to regulate multi-step metabolic pathways
The product of a pathway usually acts as an allosteric inhibitor of the first enzyme of the pathway
http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120070/bio10.swf::Feedback%20Inhibition%20of%20Biochemical%20Pathways
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Allosteric Regulation
Allows an enzyme to be temporarily
inactivated. Binding of an
allosteric effector changes the
shape of the enzyme,
inactivating it while the effector
is still bound.
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Long Weekend Homework
1) Complete Jmol activity- if not already done
2) Read pg 50-56 (make notes)
3) Complete pg 57 #2,6,8,10,12
4) Edmodo Challenge: Choose one career profile to read (Cheese Plant Manager or Marvellous Mutant) and comment on your reactions to the reading in a 2-4 sentence post