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82 Cards in this Set
- Front
- Back
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Are most enzymes proteins, and small exception
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YES, exception is catalytic RNA
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What does enzyme activity depends on
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native protein conformation
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What other other compenents some enzymes require for activity
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cofactors and coenzymes
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What are cofactors are they used up in a reaction
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are non-protein groups that bind to the enzyme--NOT USED UP IN A REACTION
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What are coenzymes, and are they used up
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subtrate for an enxymes, acts as transient carreries of a chemical (USED UP)
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Although coenzymes are USED UP, what at they kept at in cell
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CONSTANT, steady state
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What is an example of a coenzyme
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Tetrahydrofolate, coenzyme for Thymidylate Synthase
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What is Thymidylate Synthase considered
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as a target for cancer theryapy since cancer cell replicate rapidly
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What is an example of a cofactor
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MG+2--require for ATPase's
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What is a prosteic group
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non-proteib that is tightly bond to enzyme
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Most chemical reations are very slow, so what are benifits of enzymes
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speed up chemical reaction so they occur at useful rate
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Where do enzyme-catylzed reaction take placew
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within the pocket of enzyme called active site
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What is the molecule call that binds to the active site
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substrate
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2 points What is surface of active site lined with
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aa's, which SPECIALLY recognized substrate, and accelerate the chemical reaction
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Does specificity guarantee rate acceleration
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NO
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Is equilibrium affected by a catlyst
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NO
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Does Keq remain constant, what happens if you add P
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so P would convert back to S
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NEgative G determines that reaction will occur spontaneously, but it says nothing about
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RATE
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Is it true that once a TS is formed a single bond vibration is suffient to push the reaction to either S or P
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YES
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What does the rate of reaction depend on and related to G
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rate at which ground strutres can form TS--Larger G, slowers the reaction, samller G inrease reaction
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Is TS a reaction intermideate
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NO, IT DOES NOT EXISTS
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What is ground state
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starting point of reaction
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IF bond formation is favorable H is, and was is H if unfavorable
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H is NEGATIVE is favorable
H + is UNFAVORABLE |
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Is Positve S favorble and mean--
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YES, ENTROPY (disorder always increases), number of configuations available to sysmtem
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What is the reaction RATE or velocity determined by
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k (rate constant) and teh concetnration of reactants
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Is rate constant the reaction rate
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NO--reaction rate depends on both constant, and concentration of reactants
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What happens to rate constant with a high G, and larger activation barrier
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smaller rate CONSTANT, and SLOWER VELOCITY
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What does RATE constant really mean for 2-1s
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PERCENTAGE or probability that S will react to form P in one sec
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How do catalyst speed up chemical reactions
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by stabilizing the TS so G of transition state is lowered
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What kind of interactions does substrate form with active site of enzyems
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H-bonding, salt bridges, adn hydrophobics
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Must the shape of the active site accomdate the substrate
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YES
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Must the H bonding donors and acceptors adn charged groups be precisley POSITION in active site
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YES
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Since teh TS corresponds to a single structure, are bond rotations available
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NO
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What is H, and S in TS
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H is positive (unfavorble
-S (unfavorable |
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How do enzymes stablize teh TS
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enzymes active site poisition has specific aa side chain to interact with TS, such forming noncovalant bonds
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What is realtion ship bettwen G S, and H
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G=$H-$T$S
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Where is formation of TS more favorable in the bulk solution, or within the active site
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TS in active (catlyzed) reaction is less unfavorable (still unfavorable)--activation barrier is lowered
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How can active site greatly increase reaction probability in terms of proimity
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the active site can posiition the molecules precisely, so that functional groups A+B face each other, and can react
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Does reaction rate icnrease due to active site proximity effect
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YES
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Is the enzyme completmentary to substrate
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NO, this would stablize the substrate this is LOCK and KEY bad
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What is the enzyme completmentary to
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TRANSITION STATE, only a few aa code for binding of substrate, then rest are complementary to transition state--THIS IS INDUCED FIT
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3 Types of Chemistry enzymes use
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general acid/base catalysis
metal ion catalysis covalent catalysis |
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What is used for specific base catalysis, adn specific acid catalysis
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WATER base -OH
acid H30+ |
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What is used for gernal base catalysis
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COO-, NH2, S-, O-,
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What is used for gernal acid catalyst
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COOH, NH3+,
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What amino acid perform acid/base catalysis
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HAL, AG, Serine, Cysteine, Tyrosine
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What is metal ion catalysis
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metal ions can be poisitioned to stablize charged TS
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Requirements for covalent catalysis
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catalyst must be a better nucleophile than water, adn covalent imtermediate must be removed by water (hydrolysis)
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What G is affected in enzyme catalysis
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NOT stand G0---ONLY G in the transistion state
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What is pre-steady kinetics
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when the enzyme is first mixed with a large excess of substrate ES concentrations increase-
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What is kinetics is mointor approach of catalyzed reaction
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pre-steady state
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What kinetcs the the reaction velocity measured
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ONLY steady STATE
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In what state is ES constant
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steady state
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What is steady state
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EQUILIBRIUM that the rate of formation of ES is equal to rate of breakdown
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What must be in great concentration for a SS to occur
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substrate
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When is Km equal to the substrate concentration
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Vo=0.5 Vmax
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What determines Velocity max
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when enzyme is saturated, kcatX E0
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What is KCat
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how much substrate is being converted to product, equal to rate and K2
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What is Km
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AMOUNT substrate concentration wehre V0=.5 Vmax
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What is catalytic perfection
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enzymes that turnover substrate as fast as the enzyme and substrate diffuse together
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For any schemes werhe the enzyme has a single active site, the SS kinetic will be what type of curve
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hyperbolic curve
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When is Km=KD
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K-1> K2 and ES>EP
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When is Kcat equal to K1
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when Substrate concentration is less then So<Km
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What are 3 types of inhibition
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competivie, uncompetitive and mixed
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What is competive inhibition
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the inhibitor competes with the substrate for the binding site of the enzyme
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What values are affected by competive inhibition
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km is increased, b/c inhibitor is binding to enzymes Kcat not affected, b/c it is RATE as which ES becomes product
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How can competeive inhibition be overcome
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add more substrate
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What is uncompetive inhbitior
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the inhibitior binds at a site distinct from activfe site
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What inhibitor only binds to ES complex
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uncompetive inhibitor
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What values effect uncompetivie inhibitor
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kcat Decreased, adn KM decreased
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What is mixed inhibitor
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combination of both
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When does Y intercept change
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when K cat affected (uncompetive and mixed)
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What type of inhibitor is methotrexate
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competive inhibitor
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What are examples of irreverible inhibitors
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Penicllin, adn ASA
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What are suicide inactivators
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irreversible inhibitors, unreactive until bind to acitve site then combine irresibly with enzymes
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What is drug benefit of suicidie inactivators
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unreactive until reaches enzymes active site, so few side effects
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What type of inhibition is Vmax the same
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competive
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What are allosteric enzymes function
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change shape when molecules binds, servee as regulatory checkpoints along various pathways
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What are regions of allosteric enzymes
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have both catlytic domains, adn regulatory domains
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Where does positive effector molecules bind to activate cataylsis
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to regulatory--WHICH ACTIVES catalytic domain
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What is homotropic coopertativity
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wehere an allosteric enzymes may be activated by its own substrate
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Why is allosteric modulation so important
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small changes in effector or substrate concentration, can result in large changes in enzyme activity--turn on or OFF
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