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What are enzymes? Enzymes are Proteins ( (tertiary and quaternary structures). Image: Levels of protein structure, M RuizLevels of protein structure From the Virtual Cell Biology Classroom on ScienceProfOnline.comVirtual Cell Biology ClassroomScienceProfOnline.com
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EnzymesEnzymes
Apple ExperimentCome and get 2 slices of apples ( A & B – keep
separate), paper towel and a bottle of lemon juice.
When you get back to your seat:1. Write A & B on paper towel. Place apple A on A side and apple B on B side2. Immediately squeeze lemon juice over apple slice B.
3. IMPORTANT! Don’t get lemon juice all over both slices.
4. Set your apple slices aside and return the lemon juice bottle.
From the Virtual Cell Biology Classroom on ScienceProfOnline.com
What are What are enzymes?enzymes?
• Enzymes are Proteins
((tertiary and quaternary structures).
Image: Levels of protein structure, M RuizFrom the Virtual Cell Biology Classroom on ScienceProfOnline.com
Why Are Enzymes So Important?
Why are we devoting one whole lecture topic to a protein molecule?
Nearly all chemical reactions in
biological cells need enzymes to make the reaction occur fast enough
to support life.
Image: Jumping rope, Meagan E. Klein
From the Virtual Cell Biology Classroom on ScienceProfOnline.com
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What Are Enzymes?What Are Enzymes?• Acts as a Catalyst. Catalyst. AA catalystcatalyst speeds up speeds up
a chemical reaction.a chemical reaction.
• Not permanentlyNot permanently changed in the process
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EnzymesEnzymes•Are specific
for what they will catalyzecatalyze
•Are ReusableReusable•End in –asease
-Sucrase-Sucrase-Lactase-Lactase-Amylase-Amylase
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How do enzymes Work?How do enzymes Work?Enzymes work by weakening weakening bondsbonds which which lowers lowers activation activation energyenergy
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EnzymesEnzymes
FreeEnergy
Progress of the reaction
Reactants
Products
Free energy of activationFree energy of activation
Without EnzymeWith Enzyme
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•fit with substrate like a ____ and ____.
Enzymes…Enzymes…
From the Virtual Cell Biology Classroom on ScienceProfOnline.com
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Enzyme-Substrate ComplexEnzyme-Substrate ComplexThe substancesubstance
(reactant) an enzymeenzyme acts on is the substratesubstrate
EnzymeSubstrate Joins
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Active SiteActive Site• A restricted regionrestricted region of an enzymeenzyme
molecule which bindsbinds to the substratesubstrate.
EnzymeSubstrate
Active Site
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•Enzymes can Enzymes can break apart break apart substances or substances or put substances put substances together.together.
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What Affects Enzyme Activity?What Affects Enzyme Activity?
• Three factors:Three factors:1.1. Environmental ConditionsEnvironmental Conditions
2.2. Cofactors and CoenzymesCofactors and Coenzymes
3.3. Enzyme InhibitorsEnzyme Inhibitors
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1. Environmental Conditions1. Environmental Conditions 1. Extreme1. Extreme Temperature Temperature are the are the
most dangerousmost dangerous- - high tempshigh temps may denature denature (unfold) (unfold) the enzyme. enzyme.
2.2. pHpH (most like 6 - 8 pH near (most like 6 - 8 pH near neutral)neutral)3.3. Ionic concentrationIonic concentration (salt (salt ions)ions)
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2. Cofactors and Coenzymes2. Cofactors and Coenzymes• Inorganic substances Inorganic substances (zinc, iron)(zinc, iron) and
vitaminsvitamins are sometimes needed for proper enzymatic activityenzymatic activity.
• Example:Example:IronIron must be present in hemoglobinhemoglobin
in order for it to pick up oxygen.pick up oxygen.
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InhibitorsInhibitors Competitive inhibitorsCompetitive inhibitors:: are
chemicals that resembleresemble an enzyme’s normal substrateenzyme’s normal substrate and competecompete with it for the active active sitesite.
EnzymeCompetitive inhibitor
Substrate
Meet the Enzyme: Catecholase
_________ juice and other acids are used to preserve color in fruit, particularly apples, by lowering the ____ and removing the copper (cofactor) necessary for the enzyme to function.
Reaction: catecholase
catechol + O2 ---------- polyphenol colorless substrate brown product
Images: Apples, T. Port; Lemons, André Karwath; Enzyme with Cofactor, Wiki; pH scale, Edward Stevens, Wiki
From the Virtual Cell Biology Classroom on ScienceProfOnline.com
Look at your apple slices• Observe and write down
any differences in slices.• Do you think the lemon
juice had an effect on apple?
• What do you think happened? Please explain.
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Confused? Here are some links to fun resources that
further explain enzymes:• Enzymes Main Page on the Virtual Cell Biology Classroom of
Science Prof Online.• “How Enzymes Work” an animation from McGraw-Hill.
• Interactive Enzyme Tutorial and quiz from Life: The Science of Biology.
• “The Role Enzymes Play in the Body” from Enzymedica. These guys are selling supplements. I don’t endorse the supplement, but their video is very instructive regarding enzymes and digestion.
• “Assignment Discovery: Enzyme Catalysts” from HowStuffWorks, a Discovery Company.
• “Enzymes and Digestion” from About.com.
• “Bio Rad GTCA Song” musical advertisement for SsoFast™.
• And why not sing “Goodtimes with Enzymes” to the Chic song “Goodtimes.” See next slide for lyrics.
(You must be in PPT slideshow view to click on links.)From the Virtual Cell Biology Classroom on ScienceProfOnline.com
