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Slide 1
Slide 2
AP Biology 2007-2008 Enzymes
Slide 3
AP Biology Exothermic vs. endothermic reactions
exothermicendothermic - energy released - digestion - energy
invested - synthesis -G-G G = change in free energy = ability to do
work +G+G All chemical reactions require energy
Slide 4
AP Biology Activation energy Breaking down large molecules
requires an initial input of energy activation energy large
biomolecules are stable must absorb energy to break bonds energy
cellulose CO 2 + H 2 O + heat
Slide 5
AP Biology Too much activation energy for life Activation
energy moves the reaction over an energy hill Why is activation
energy important?? glucose
Slide 6
AP Biology Reducing Activation energy Catalysts reducing the
amount of energy to start a reaction Pheeew that takes a lot less
energy! reactant product uncatalyzed reaction catalyzed reaction
NEW activation energy
Slide 7
AP Biology Catalysts So whats a cell got to do to reduce
activation energy? get help! chemical help ENZYMES GG Call in the
ENZYMES! The ENZYMES are here
Slide 8
AP Biology Enzymes Biological catalysts Proteins facilitate
chemical reactions increase rate of reaction without being consumed
reduce activation energy dont change free energy ( G) released or
required required for most biological reactions highly specific
thousands of different enzymes in cells control reactions of
life
Slide 9
AP Biology Enzymes vocabulary substrate reactant which binds to
enzyme enzyme-substrate complex: temporary association product end
result of reaction active site enzymes catalytic site; substrate
fits into active site substrate enzyme products active site
Slide 10
AP Biology Lock and Key model Simplistic model of enzyme action
substrate fits into 3-D structure of enzyme active site H bonds
between substrate & enzyme like key fits into lock In biology
Size doesnt matter Shape matters!
Slide 11
AP Biology Induced fit model More accurate model of enzyme
action 3-D structure of enzyme fits substrate substrate binding
cause enzyme to change shape leading to a tighter fit
conformational change bring chemical groups in position to catalyze
reaction
Slide 12
AP Biology Properties of enzymes Reaction specific each enzyme
works with a specific substrate H bonds & ionic bonds between
active site and substrate Not consumed in reaction single enzyme
molecule can catalyze thousands or more reactions per second
Affected by cellular conditions any condition that affects protein
structure temperature, pH, salinity - Denaturation
Slide 13
AP Biology Naming conventions Enzymes named for reaction they
catalyze sucrase breaks down sucrose proteases break down proteins
lipases break down lipids DNA polymerase builds DNA adds
nucleotides to DNA strand pepsin breaks down proteins
(polypeptides)
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AP Biology 2007-2008 Got any Questions?!
Slide 15
AP Biology 2007-2008 Factors that Affect Enzymes
Slide 16
AP Biology Enzyme concentration enzyme concentration reaction
rate Whats happening here?! as enzyme = reaction rate
Slide 17
AP Biology Substrate concentration substrate concentration
reaction rate Whats happening here?! as substrate = reaction
rate
Slide 18
AP Biology 37 Temperature temperature reaction rate Whats
happening here?! Optimal T o Slow molecules Denaturation Optimum T
greatest number of molecular collisions
Slide 19
AP Biology Enzymes and temperature Different enzymes function
in different organisms in different environments 37C temperature
reaction rate 70C human enzyme hot spring bacteria enzyme
(158F)
AP Biology Salinity salt concentration reaction rate Whats
happening here?! Salinity is salt concentration
Slide 22
AP Biology Compounds which help enzymes cofactors non-protein
small inorganic compounds & ions bound within enzyme molecule
Examples: Mg, K, Ca, Zn, Fe, Cu IMPORTANT!!!!! So sit up! coenzymes
non-protein organic molecules bind temporarily or permanently to
enzyme near active site Examples: many vitamins NAD (niacin; B3)
FAD (riboflavin; B2) Coenzyme A
Slide 23
AP Biology Show me some coenzymes homeskillet! Mg in
chlorophyll Fe in hemoglobin
Slide 24
AP Biology Compounds which regulate enzymes Inhibitors
molecules that reduce enzyme activity competitive inhibition
noncompetitive inhibition feedback inhibition
Slide 25
AP Biology Competitive Inhibitor Inhibitor & substrate
compete for active site disulfiram (Antabuse) treats chronic
alcoholism blocks enzyme that breaks down alcohol severe hangover
& vomiting 5-10 minutes after drinking How can I beat a
competitive inhibitor?
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AP Biology Non-Competitive Inhibitor Inhibitor binds to site
other than active site allosteric inhibitor binds to allosteric
site causes enzyme to change shape conformational change active
site is no longer functional binding site keeps enzyme
inactive
Slide 27
AP Biology Metabolic pathways A B C D E F GA B C D E F G enzyme
1 enzyme 2 enzyme 3 enzyme 4 enzyme 5 enzyme 6 Many enzymes are
used in chemical reactions efficiency control = regulation A B C D
E F GA B C D E F G enzyme When might Inhibitors be helpful?
Slide 28
AP Biology allosteric inhibitor of enzyme 1 Feedback Inhibition
Regulation & coordination of production product is used by next
step in pathway final product is inhibitor of earlier step
allosteric inhibitor of earlier enzyme feedback inhibition no
unnecessary accumulation of product A B C D E F GA B C D E F G
enzyme 1 enzyme 2 enzyme 3 enzyme 4 enzyme 5 enzyme 6 X
Slide 29
AP Biology Feedback inhibition Example synthesis of amino acid,
isoleucine from amino acid, threonine isoleucine becomes the
allosteric inhibitor of the first step in the pathway as product
accumulates it collides with enzyme more often than substrate does
threonine isoleucin e
Slide 30
AP Biology 2007-2008 Dont be inhibited! Ask Questions!
Slide 31
AP Biology Extra Info
Slide 32
AP Biology Factors affecting enzyme function pH changes in pH
adds or remove H + disrupts bonds, disrupts 3D shape disrupts
attractions between charged amino acids affect 2 & 3 structure
denatures protein optimal pH? most human enzymes = pH 6-8 depends
on localized conditions pepsin (stomach) = pH 2-3 trypsin (small
intestines) = pH 8 72013456891011
Slide 33
AP Biology Factors affecting enzyme function Salt concentration
changes in salinity adds or removes cations (+) & anions ()
disrupts bonds, disrupts 3D shape disrupts attractions between
charged amino acids affect 2 & 3 structure denatures protein
enzymes intolerant of extreme salinity Dead Sea is called dead for
a reason!