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67 Cards in this Set
- Front
- Back
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What is the "Vital force" theory?
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Inability to reproduce biochemical reactions in lab
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"Ferments" -
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Caused biological reactions
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What was term enzyme coined as in 1878?
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Something in yeast as opposed to yeast itself
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Who came up with cell-free extract alcoholic fermentation?
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Eduard Buchner
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What is chemical reaction for cell-free extract alcohol fermentation?
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C6H12O6 -> 2CH3CH20H + 2CO2
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In 1926, James Sumner crystallized _________________ and demonstrated it a protein.
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Jack bean urease
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How much faster are enzyme reactions than uncatalyzed reactions?
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10^6 - 10^12 higher
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What are the reaction conditions for enzyme?
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temp of less than 100 C, atm pressure and neutral pH - milder reaction conditions
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T/F Enzyme has greater reaction specificity and rarely has side products when compared to other catalysts.
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True
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How does allosteric control affect enzyme?
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It can affect T-> R configuration.
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What is confusing about enzyme nomenclature?
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"ase" is used to end substrate's name but it is also used at end of phrase describing action; there are multiple names for same enzyme or same name for different reactions; some names provide no clue to reaction
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What is name of standard naming system for Enzymes?
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International Union of Biochemistry and Molecular Biology (IUBMB)
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How does IUBMB classify enzymes?
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Enzymes are classified by nature of reaction; 6 major classes with subclasses; Systematic name and common name for most enzymes; IUBMB name followed by EC plus set of numbers
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What are 6 main groups of enzymes?
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Oxidoreductases, transferases, hydrolases,lyases, isomerases, ligases
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Describe the geometric complementarity between enzyme and substrate.
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Lock and Key formation
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What is induced fit substrate specificity?
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Enzyme undergoes conformational change with substrate binding
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What is stereospecificity of substrate necessary?
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Strict 3 D requirements due to chiral atoms and asymmetric binding sites
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What does geometric specificity of substrate range from?
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strict - only accept 1 substrate - preferences, accepts related substrates, to having preferences
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What is treatment for methanol poisoning?
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Ethanol doping to competitively inhibit ethanol enzyme - formaldehyde
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What enzyme turns citrate into isocitrate by adding an OH group?
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Aconitase
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What enzyme turns peptide and ester into ions?
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Chymotrypsin
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What are enzymes quite proficient at?
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Acid base reactions, transient covalent bonds, charge-charge interactions
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What are enzymes less proficient at?
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Oxidation reductions, group transfer reactions
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What is required for the reactions that enzymes are less proficient at ?
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Co factors
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What are three categories of cofactors?
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metal ions, organic molecules - conenzymes, and prosthetic groups
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Describe metal ions as cofactors.
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EX: Cu +2, Fe +3, Zn +2 - explains need for dietary elements, explains heavy metal toxicity - same group metal ion can replace normal ion and render enzyme inavtive
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Organic molecules, "coenzymes" almost function as ___________.
What are examples? |
Cosubstrates; NAD+, NADP+, FAD
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Describe prosthetic groups as cofactors.
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Prosthetic groups are permanently associated with enzyme often by covalent bond.
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What is an example of prosthetic group?
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Heme prosthetic group in cytochromes
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What is a catalytically active enzyme cofactor complex called?
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Holoenzyme
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What is an inactive enzyme called?
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apoenzyme
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What are transient coenzymes?
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They must be regenerated in another enzymatic reaction
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Apoenzyme + cofactor -> _________
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Holoenzyme
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Why must coenzymes be regenerated?
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They chemically change in catalytic reaction. They must be regenerated by different enzyme since they are transiently bound.
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How are prosthetic groups regenerated?
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They are regenerated as part of catalytic reaction
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Which vitamins are cofactors?
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Water soluble vitamins
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Which vitamins are not cofactors?
Why are they required? |
Fat soluble vitamins A and D, they are still diet required as precursor molecules
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What cofactor is used to make ethanol into acetaldehyde with enzyme ADH>
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NAD+
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T/F NAD and NADP are interchangeable.
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False
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NAD is involved in ? NADP is used for ?
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- redox breakdown, - synthesize biomolecules
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Understanding of enzyme catalysis comes from __________________ from 1930's.
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Transition State Theory
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What is the TS theory?
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When a reaction state occurs, transition period will be produced. There must be sufficiently high energy to form the TS bonds. Transition involves bond forming and bond breaking
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Reactions approach along path of minimum free energy also called __________.
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Reaction coordinate
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What is transition state diagram or reaction coordinate diagram?
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Plot of reaction coordinate vs free energy
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_________ and __________ are states of minimum free energy.
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Reactants and Products
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_______________ is highest point or greatest free energy.
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Transition state
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What is free energy of activation?
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Free energy transition state minus reactants
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Why wouldn't a transition state diagram not be symmetrical?
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Free energy difference between reactants and products
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What is time passage through transition state?
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10^-13 - 10^-14; very short half life since concentration is small
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What is rate limiting step of entire reaction?
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Decomposition of transition state to products or back to reactants
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What is reaction rate according to thermodynamics?
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e^(-GTS/RT); R is gas law constant and T is absolute temperature
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What happens to reaction rate with greater G (TS)?
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Slower reaction rate since requires greater energy and takes more time
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What happens to thermal energy of reactants if G(TS) increases?
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Thermal energy decreases
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What happens to reaction rate and thermal energy of reactants if G(TS) decreases?
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They both increase
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How many TS and Activation energy barriers are there for 2 step reaction?
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2 and 2
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What is the speed between the two if 1st step activation energy is greater than 2nd step activation energy?
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1st step is slower
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In multi step reactions which step is rate determining?
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Step with greatest TS Free energy is "bottleneck" or rate determining step
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Catalysts reduce ________.
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TS Free energy - G
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What type of reaction pathway do enzymes provide?
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TS free energy lower than uncatalyzed reaction
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What is rate enhancement ratio?
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Catalyzed/uncatalyzed reaction
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Catalysts work by lowering ____.
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Activation Energy
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A 10 fold increase rate enhancement is about what difference in TS energies? A million fold increase? at 25C
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5.71 kJ/mol and 34kJ/mol
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T/F Catalysts lower TS free energy barrier by same amount for both forward and reverse reactions.
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True
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What does likelihood of forward or reverse reaction depend on?
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Free energy difference between reactants and products
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When is forward reaction spontaneous?
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If Free energy of Reaction (G reaction) is less than 0
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When is reverse reaction spontaneous?
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G reaction greater than 0
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T/F Enzymes can alter total change in G reaction and G (TS).
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False. Enzymes can not alter total change in G reaction but only decrease G TS to alllow reaction to approach equilibrium faster than without catalyst
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