BIOCHEM Exam 2

Enzymes are _______, so they act on many/limited substrates

- specific

If Q = K then the reaction is:

- at equilibrium

Lineweaver-Burk Plot

inverse of Michaelis-Menten Equation

What is enthalpy?

the heat content of a system

Single Substrate Reactions

- A --> B + C - rate directly proportional to concentration of substrate

Which of the following statements about metabolism is correct? A. Anabolism breaks down complex molecules into simpler ones, which requires a net input of energy, while catabolism synthesizes complex molecules from simpler ones, which yields a net release of energy B. Catabolism breaks down complex molecules into simpler ones, which requires a net input of energy, while anabolism synthesizes complex molecules from simpler ones, which requires a net release of energy. C. Anabolism breaks down complex molecules into simpler ones, which yields a net release of energy, while catabolism synthesizes complex molecules from simpler ones, which requires a net input of energy. D. Catabolism breaks down complex molecules into simpler ones, which yields a net release of energy, while anabolism synthesizes complex molecules from simpler ones, which requires a net input of energy.

- Catabolism breaks down complex molecules into simpler ones, which yields a net release of energy, while anabolism synthesizes complex molecules from simpler ones, which requires a net input of energy.

Which of the following kinetic parameters is a measure of an enzyme's efficiency? A. Vmax B. kcat C. kcat/Km D. KM

- Kcat/Km

The Km of glucokinase for glucose is 20 mM, and the Km of hexokinase for glucose is 0.15 mM. However, hexokinase and glucokinase can also interact with fructose and catalyze the addition of a phosphate group. What, if anything, can you say about the relative affinities of the enzymes for fructose? Explain your answer.

- Km is substrate specific so exact value can't be known w/o measuring experimentally - abl eto predict hexokinase will have greater affinity b/c fructose is similar in structure to glucose & hexokinase has greater affinity for glucose

Which of the following kinetic parameters measure the rate of the reaction when the enzymes are saturated with substrate? A. kcat/KM B. kcat C. vmax D. KM

- Vmax

the location of the enzyme where the substrate(s) bind(s) is called the:

- active site

Indicate the true statements about thermodynamics: A. all chemical reactions are energy transfers B. in an endergonic reaction ΔG is negative C. exergonic reactions aren't spontaneous & capture energy D. a negative ΔG indicates that reactants have a higher free energy than products

- all chemical reactions are energy transfers - negative ΔG indicates that reactants have higher free energy than products

Enzymes can accelerate reactions by: A. correctly positioning a metal ion for catalysis B. causing strain on the bonds in a substrate C. binding a substrate or substrates in optimal orientations D. promoting the removal/addition of protons from R groups in the active site E. all of the above F. none of the above

- all of the above

The R group of an amino acid determines if it is: A. charged/uncharged B. polar/non-polar C. hydrophilic/hydrophobic D. all of the above

- all of the above

Which of the following statements, if any, about an enzyme-catalyzed reaction is/are correct? A. an enzyme speeds up the reaction rate by lowering the activation energy B. an enzyme allows more molecules to reach the transition state leading to an increase in the rate of product formation C. an enzyme doesn't change the free energy of the products/reactants D. all of the above statements are correct E. none of the above statements are correct

- all of the above statements are correct

Indicate the true statements: A. all reactions require activation energy B. activation energy is the difference in free energy between substrates and transition state C. reactions with higher activation energies have faster rates D. by lowering the activation energies via enzymes, fewer molecules have energy to reach the transition state

- all reactions require activation energy - activation energy is the difference in free energy between substrates & transition state

Reaction Kinetics

- all reactions require activation energy regardless of ΔG - reactions w/ smaller activation energies have faster rates than reactions w/ larger activation energies

Why do enzyme activity analyses most commonly measure initial velocities of reactions?

- assumes substrate concentration doesn't significantly change, amount of product is negligible & reverse reaction rate doesn't contribute - initial velocity depends on known enzyme & substrate concentrations & is beginning/linear region of curve where velocity doesn't change w/ time

Which of the following statements is FALSE? A. the free energy barrier in a chemical reaction must be overcome in order for products to form. B. at a given temperature & time all the molecules in a solution or a sample will have the same energy C. lowering the free energy of the transition state can increase a reaction rate D. an increase in temperature can result in an increased reaction rate

- at a given temperature & time all the molecules in a solution or a sample will have the same energy

Which of the following statements is TRUE: A. entropy is a measure of order B. biological systems expend energy to overcome entropy C. biological systems are highly ordered so entropy changes are not relevant D. entropy of an isolated system will tend to level to a minimum value

- biological systems expend energy to overcome entropy

For any chemical reaction, what will happen to the rates of the forward & reverse reactions when an enzyme is added? A. both the forward & reverse rates of a reaction decrease B. both the forward & reverse rates of a reaction increase C. the forward rate increases while the reverse rate decreases D. the forward rate decreases while the reverse rate increases

- both the forward & reverse rates of a reaction increase

The ΔG° of a reaction: A. can predict whether a reaction will be thermodynamically favorable under standard conditions B. is not related to the equilibrium constant C. will change if the concentration of reactants & products are changed D. indicates how quickly the reaction occurs

- can predict whether a reaction will be thermodynamically favorable under standard conditions

Enzymes are ______ which means that they are unchanged from start to end of the reaction

- catalysts

Reaction Rate

- change in product concentration/T

Select ALL TRUE statements about enzyme cofactors/coenzymes A. coenzymes or cofactors are irreversibly changed during catalysis B. the coenzyme NAD+ is derived from the vitamin niacin & is essential for cellular respiration C. cofactors are optimal, but optional. Organisms can function normally without cofactors D. Fe & Zn are metals that serve as enzymatic cofactors

- coenzyme NAD+ is derived from the vitamin niacin & is essential for cellular respiration - Fe & Zn are metals that serve as enzymatic cofactors

A reaction at equilibrium can be driven in one direction or the other by changing the _______ of reactants or products A. melting point B. temperature C. volume D. concentration

- concentration

Serine proteases make use of ______ catalysis as well as ______ stability of the transition state to achieve rate enhancement A. non-covalent, hydrogen-bonding B. covalent, electrostatic C. non-covalent, electrostatic D. covalent, hydrogen-bonding

- covalent, electrostatic

How do enzymes change reaction rates?

- decreases activation energy - with a lower ΔG, more molecules will have enough energy to reach transition state & form more products

General Acid Catalysis

- donates proton to an atom that develops negative charge in transition state

Many enzymes operate using an acid catalysis mechanism; during this reaction an amino acid R group functions as an acid by: A. donating a proton B. accepting a water molecule C. accepting a proton D. donating a water molecule

- donating a proton

A spontaneous reaction is defined as one where: A. the reaction happens quickly B. the energy change is zero C. energy is absorbed D. energy is released

- energy is released

What is activation energy?

- energy needed to reach transition state

Catalysts affect the ______ of a chemical reaction A. thermodynamics B. energy of product formation C. energy of activation to the transition state D. energy of substrate formation

- energy of activation to transition state

The change in ______ for the complete oxidation of a fatty acid is the same, whether it occurs via a biochemical pathway or combustion to CO2 & H2O A. entropy B. free energy C. heat capacity D. enthalpy

- enthalpy

When Leonor Michaelis and Maude Menten first derived the Michaelis-Menten equation they made some assumptions. Select EACH statement that describes an assumption of the Michaelis-Menten model. A. the enzyme can reach maximal velocity when saturated with substrate B. the Vmax can be calculated by multiplying the Km by 2 C. the formation of ES from E + P is so small that this rate can be ignored D. the rate of formation of ES is equal to the rate of loss of ES

- enzyme can reach maximal velocity when saturated with substrate - formation of ES from E + P is so small that this rate can be ignored - rate of formation of ES is equal to rate of loss of ES

Which is appropriate for initial rate method experiments to analyze an enzyme-catalyzed reaction? A. substrate concentration is constant & rate is measured at different concentrations of enzyme B. both enzyme & substrate concentrations are constant. The temperature is varied & the rate is measured C. enzyme concentration is constant & rate is measured at different substrate concentrations D. substrate & enzyme concentrations are varied inversely with respect to one another and the rate is measured

- enzyme concentration is constant & rate is measured at different substrate concentrations

Which is appropriate for initial rate method experiments to analyze an enzyme-catalyzed reaction? A. the substrate & enzyme concentrations are varied inversely with respect to one another & the rate is measured B. the enzyme concentration is constant and the rate is measured at different substrate concentrations C. both enzyme and substrate concentrations are constant. temperature is varied & rate is measured D. substrate concentration is constant & rate is measured at different concentrations of enzymes

- enzyme concentration is constant and the rate is measured at different substrate concentrations

Which of the following statements correctly describe enzymes? Select ALL that apply. A. enzymes are highly efficient, allowing a reaction to proceed in a biologically useful time frame B. all enzymes are proteins C. enzymes generally bind to one or a few substrates making them highly specific D. enzymes make the delta G of a reaction more negative & therefore, more favorable

- enzymes are highly efficient, allowing a reaction to proceed in a biologically useful time frame - enzymes generally bind to one or a few substrates making them highly specific

Why don't enzymes change the ΔG or Keq of a reaction? Can an enzyme make a non spontaneous reaction favorable? Why or why not?

- enzymes make reactions faster by lowering free energy of the transition state - don't change ΔG or Keq b/c they don't affect the beginning or end states; can't make a non spontaneous reaction favorable since overall free energy doesn't change

When Keq = 1 at equilibrium, then [products] _______ [reactants]

- equal

A reaction at its lowest energy state for the system & with equal rates in the forward & reverse directions is said to be under _______ A. equilibrium conditions B exergonic conditions C. endergonic conditions D. anaerobic conditions

- equilibrium conditions

Explain how the hydrophobic effect contributes to folding of a globular protein. Which amino acids do you predict to find on the inside? Outside? Active site?

- explains why they clump together in an aqueous environment in order to maximize entropy in water by minimizing number of ordered water molecules that surround hydrophobic molecules - causes hydrophobic R groups in polypeptide chain to clump together inside a folded 3-D protein & hydrophilic orient themselves outside

True or False: The equilibrium constant of a reaction is not related to the change in free energy of the reaction.

- false

True or False: the equilibrium constant of a reaction can change in the concentration of reactants & products are changed.

- false

Does the reaction rate increase/decrease in presence of an enzyme?

- fast at beginning and decreases over time as substrates is used

The flow of material through a metabolic pathway is called the ________ A. flux B. degree of amplification C. current D. cascade effect

- flux

Protein Folding

- fold spontaneously - covalent & non-covalent interactions contribute to protein folding - many fold so hydrophobic is inside & hydrophilic is outside(enzymes) - hydrophobic/hydrophilic amino acids don't cluster in primary sequence

Enzymes catalyze the _______ and ______ of a reaction. They are dictated by ______

- forward & reverse; ΔG

If Q < K then the reaction proceeds in the:

- forward direction

Which of the following describes an unfavorable reaction? A. reaction will be very slow without a catalyst B. the free energy change for the reaction is positive C. at equilibrium the reactants, not the products, are favored D. both B & C are correct E. A, B, C are correct

- free energy change for the reaction is positive - at equilibrium, the reactants not the products, are favored

Define free energy & describe the two components

- free energy is a quantitative measure of useful work - composed of enthalpy & entropy

Select all characteristics/parameters that will change when an enzyme catalyzes a chemical reaction. A. free energy of transition state B. rate of reaction C. standard free energy change D. free energy of reactants E. concentrations of reactants & products at equilibrium

- free energy of transition state - rate of reaction

ΔG of a Reaction

- free energy products - free energy reactants - zero at equilibrium; forward/reverse reactions still occur there just isn't an overall change - concentration of products & reactants aren't necessarily equal; depends on Keq

Michaelis-Menten

- graph is hyperbolic - have one active site or multiple independent active sites - Km is relevant

Allosteric

- graph is sigmoidal - must have multiple dependent active sites - exist in 2 forms w/ different substrate affinities

When Keq > 1 at equilibrium then [products] _______ [reactants]

- greater than

The T/R ratio for an allosteric enzyme is ______ when substrate concentrations are low & _________ at saturating substrate concentrations A. high; high B. low; high C. low;low D. high; low

- high; low

Alanine, valine, leucine & isoleucine are important in 3 dimensional structure because they: A. are branched B. attract water molecules C. are highly hydrophobic D. highly hydrophilic

- highly hydrophobic

What is the main driving force of protein folding?

- hydrophobic effect - water molecules form more favorable interactions w/ polar amino acids & water molecules - non-polar amino acids cluster in protein interior

Where in a globular protein is the amino acid tryptophan most likely to be located? A. hydrophilic interior B. hydrophobic interior C. hydrophilic exterior D. hydrophobic exterior

- hydrophobic interior

Which of the following is a FALSE statement about protein folding? A. intramolecular hydrogen bonds stabilize folding of a polypeptide chain B. Van der Waals interactions have a stabilizing, cumulative effect C. hydrophobic residues pack together because the side chains are attracted to each other through weak Van der Waals interactions D. Salt bridges(ionic bonds) stabilize folding of a polypeptide chain

- hydrophobic residues pack together because side chains are attracted to each other through weak Van der waals interactions

Water molecules that surround a less polar molecule in solution are: A. immobile & disordered B. mobile & ordered C. mobile & disordered D. immobile & ordered

- immobile & ordered

General Acid/Base catalysis

- important in reactions involving proton transfer

Select the TRUE statement(s) I. in a cell, a reaction is spontaneous if the ΔG° is negative II. in a cell, a reaction is spontaneous if the ΔG is negative III. in a cell, a reaction is spontaneous if an enzyme is present that can catalyze the reaction A. I only B. II only C. III only D. I & II only E. all of the above

- in a cell, a reaction is spontaneous if the ΔG is negative

Consider a situation in which the enzyme is operating at optimum temperature and pH, and has been saturated with substrate. What is your best option for increasing the rate of the reaction? A. increase pH B. increase temperature C. increase enzyme concentration D. increase substrate concentration

- increase enzyme concentration

At low substrate concentrations, addition of more substrate to a Michaelis-Menten enzyme will ________ the rate of the reaction. At saturating substrate concentrations more substrate will _______ the rate of reaction. A. increase; increase B. increase; not affect C. not affect; increase D. not affect; not affect

- increase; not affect

Does the reaction rate increase/decrease in absence of an enzyme?

- increases slowly in absence

You are assessing the activity of a recently discovered enzyme, called Loonyase,that binds to the substrate WOW. Loonyase has a single active site and a Vmax of 0.10 mM/sec. From this information, can you determine the Km of Loonyase for WOW? If so, what is the Km? If not, explain why not.

- information provided doesn't give relationship between substrate concentration & Vmax so there isn't enough information to know the value of Km

What do kinetic experiments assess?

- initial velocity

Which of the following statements BEST describes the Michaelis-Menton constant KM? (A "BEST" statement would be one that applies nearly all the time, not just part of the time.) A. it is numerically equal to the affinity between the enzyme and its substrate B. it is a measure of the maximal rate of a catalytic process C. it is numerically equal to the substrate concentration required to reach half maximal velocity for an enzyme-catalyzed reaction D. it is a measure of enzyme efficiency

- it is numerically equal to the substrate concentration required to reach half maximal velocity for an enzyme-catalyzed reaction

What does it mean if something has a high Km value?

- it will take a lot of substrate to reach 50% activity & eventually 100%

What does it mean if ΔG>0?

- it's an endergonic reaction & energy needs to be supplied

What does it mean if ΔG<0?

- it's an exergonic reaction & energy is released

When Keq < 1 at equilibrium then [products] ______ [reactants]

- less than

Explain how positive cooperativity leads to the sigmoidal shape of an allosteric enzyme activity graph. Be thorough and discuss what happens at the beginning, middle, and end of the graph. Also, include 'T form' and 'R form' in your answer.

- low [substrate] mean more subunits are in the T form & won't be bound to substrate so the activity is low - as [substrate] increases & nearly all enzymes have at least one subunit in R form & bound to substrate this results in rapid increase in activity b/c "cooperate" together - R form subunits cause neighboring subunits to shift into R form even if they aren't binding substrate

Gibbs Free Energy

- measure of "useful" energy in a transformation

The equilibrium state of a biochemical reaction is approached _______ in the presence of a catalyst A. at the same rate B. more rapidly C. not at all D. more slowly

- more rapidly

If ΔG is positive is it a spontaneous/non-spontaneous reaction?

- non spontaneous & not favorable

The formation of an enzyme-substrate complex tends to be thermodynamically favorable due to __________ interactions between the substrate & the enzyme A. non-covalent B. nominal C. carbon-based D. covalent

- non-covalent

Enzyme A and Enzyme B both catalyze the same reaction. If Enzyme A has a larger turnover number than Enzyme B, then which enzyme, if either, has a higher catalytic efficiency? A. enzyme B is more efficient because it's turnover number is smaller B. enzyme A is more efficient because it's turnover number is larger C. not enough information is provided to know for certain

- not enough information is provided to know for certain

Endergonic Reactions

- positive free energy - requires activation energy to occur - requires an enzyme

Are there any levels of protein structure that are NOT disrupted when a protein denatures? If so, which one(s)? What about when a protein is degraded?

- primary structure is left intact when a protein denatures, but degradation disrupts all levels of protein structure

What does it mean if a reaction is irreversible?

- proceeds only one direction because it is so far from equilibrium(ΔG is negative) - conditions can't be altered to make it go in the opposite direction

Which of the following describe(s) a difference between protein degradation and protein denaturation? A. protein degradation disrupts the peptide bonds, but protein denaturation doesn't B. protein degradation leads to loss of protein function, but protein denaturation doesn't C. protein degradation occurs because of the hydrophobic effect, but protein denaturation doesn't D. both A & B describe a difference E. both A & C describe a difference

- protein degradation disrupts the peptide bonds, but protein denaturation doesn't

What does it mean if a reaction is reversible?

- reactants transform into products & products can transform back into reactants - it is at equilibrium or close; can be exergonic/endergonic

What does it mean if a reaction is favorable?

- refers to spontaneity of reactants becoming products; depends on magnitude of ΔG

Exergonic Reactions

- releases energy - requires activation energy to occur - favorable(spontaneous) - free energy reactants greater than free energy products - requires enzyme

Steady State

- remains almost constant; persists until almost all of the substrate is consumed

General Base Catalysis

- removes proton from an atom that develops positive charge in transition state

If Q > K then the reaction proceeds in the:

- reverse direction

A ______ reaction or process is always near a state of equilibrium A. irreversible B. reversible C. synthesis D. degradation

- reversible

Metabolic Processes

- series of connected chemical reactions that are organized into pathways

What is the catalytic triad and why is it in different enzymes?

- set of coordinated amino acids that can be found in the active site of enzymes - especially proteases, catalytic triad breaks bonds, contains an acid, a base & nucleophile

Kcat/Km

- specificity constant(catalytic efficiency) - takes into substrate binding & speed of product formation - property of enzyme for specific substrate

If ΔG is negative is it a spontaneous/non-spontaneous reaction?

- spontaneous & favorable

ΔG°

- standard free energy change - constant for specific reactions under standard conditions

What is the difference between ΔG and the standard free energy change(ΔG°)? Which one is always the same for a specific reaction? Why?

- standard free energy change always the same when measured at standard conditions since it represents free energy change at equilibrium - ΔG distance from equilibrium state of a given reaction & varies depending on concentrations of reactants & products in a cell

Catalyst

- substance that increases rate of a chemical reaction w/o being changed in overall process - doesn't affect thermodynamic favorability of a reaction; just reaches equilibrium more quickly - most are proteins; some are RNA

Steady state conditions in an enzyme catalyzed reaction occur when: A. the substrate concentration is high & the reaction rate is not changing B. the substrate concentration is low & the reaction rate changes linearly C. the reaction rate is ~50% and each addition of substrate causes the rate to increase by the same amount each time

- substrate concentration is high & the reaction rate is not changing

What is Km?

- substrate concentration when rate is 1/2 Vmax - how quickly an enzyme reaches max activity - can be a measure of affinity - property of enzyme for specific substrate; not dependent on concentration of enzyme

What are rates of reaction determined by?

- the activation energy; not ΔG

When a reaction is at equilibrium, which of the following is/are TRUE? Select ALL that apply. A. the biochemical reaction is reversible B. the rates of the forward & reverse reactions are equal C. the K value is equal to 1 D. the concentrations of the products & reactants are equal

- the biochemical reaction is reversible - the rates of the forward & reverse reactions are equal

Which of the following characteristic, if any, is a unique property of a Michaelis-Menten enzyme as compared to an allosteric enzyme? A. the graph of V0 vs [S] for the enzyme is hyperbolic B. the enzyme can catalyze both the forward & reverse reaction C. there are 2 forms of the enzyme each with a different activity & a different substrate affinity D. none of the above is a unique property of a Micahelis-Menten enzyme

- the graph of V0 vs [s] for the enzyme is hyperbolic

Substrate

- the substance that is acted on by an enzyme

The terms Q and K refer to reaction components at non-equilibrium and equilibrium conditions, respectively. For a forward reaction to be favored in a living cell, which of the following statements describes the relationship between Q and K? A. the value of Q must be less than that of K B. the value of K must be less than that of Q C. no conclusion can be drawn about Q & K for a favorable process D. cells are at equilibrium so none of the above statements are true

- the value of Q must be less than that of K

Water molecules clustered around non polar molecules contribute to hydrophobic interactions because: A. non polar molecules are more highly organized than polar molecules B. their number is minimized to increase the total entropy of water C. water molecules in the cell are more organized in the regions away from the non polar molecule D. water molecules will aggregate around non polar molecules

- their number is minimized to increase the total entropy of water

Why does an enzyme interact most strongly with the transition state & not the reactants?

- transition state is physical state that a reactant must pass through to reach product - role of an enzyme is to lower free energy of the transition state so more reactant molecules can reach this transition state in a given period of time - maximizies number of interactions with a high energy conformation; stabilizing & reducing free energy of the transition state & allowing more molecules to adopt this shape

An enzyme changes the free energy of the _______ A. products and the transition state, but not the reactants B. reactants, transition state & the products C. transition state, but not the products or reactants D. reactants & transition state, but not the products

- transition state, but not the products or reactants

One mechanism enzymes use to achieve their rate enhancement of reactions is a preferential binding to the ________ through complementary non-covalent interactions that _________ the energy needed to reach the intermediate A. transition state; increase B. reactants; increase C. transition state; decrease D. reactants; decrease

- transition state; decrease

Enzymes form the most favorable interactions with the __________. What is this theory called?

- transition state; induced fit theory

What's the difference between turnover number and the specificity constant?

- turnover number measures number of substrate molecules turn over per enzyme molecule/unit time when enzyme is saturated w/ substrate - specificity constant is distinct since it also factors in affinity of enzyme for any given substrate(s)

What is Kcat?

- turnover number(how quickly an enzyme can catalyze a reaction after binding to substrate) - property of enzyme for specific enzyme - values are independent of how much enzyme you're using

Denaturation

- unraveling of protein shape - non-covalent interactions & disulfide bonds can be disrupted - doesn't break peptide bonds - refolding is possible in certain cases/conditions

You are given a biochemical reaction and a ΔG. When will the reaction proceed as written(from left to right)? A. when ΔG=0 B. when ΔG is much greater than 0 C. when ΔG is much less than 0 D. not enough information is provided to know for certain

- when ΔG is much less than 0

What does ΔG of a reaction indicate?

- whether a reaction releases/requires energy

You perform an enzyme activity assay using 1.0 mM of enzyme and determine that the Vmax is 0.5 mM/sec. If you repeated the assay using 2.0 mM of enzyme, would that affect Vmax? If so, how? Explain your answer.

- yes; Vmax would increase because there are more active sites available at every substrate concentration so the substrate can be used up more quickly leading to rate increase

What is the ΔG at equilibrium & what does it mean? Does the reaction stop?

- ΔG = 0 at equilibrium - reaction doesn't stop; the forward and reverse reactions are happening at the same time

Which of the following statements correctly compare(s) ΔG and ΔGº′? A. Both ΔG and ΔGº′ are equal to zero at equilibrium. B. Even if the concentrations of products and reactants in a chemical reaction change, both ΔG and ΔGº′ remain the same. C. ΔG is a measure of the actual free energy change of a reaction in a cell and ΔGº′ is a measure of the free energy change under biochemical standard conditions, which mimic physiological conditions. D. All of the above statements are correct.

- ΔG is a measure of the actual free energy change of a reaction in a cell and ΔGº′ is a measure of the free energy change under biochemical standard conditions, which mimic physiological conditions.

ΔG° equation

-RTln(Keq)

Under standard conditions, a given reaction is endergonic (i.e., ΔG° >0). Which of the following can make the ΔG for the reaction favorable? 1) using the product immediately in the next step 2) maintaining a high starting-material concentration 3) keeping a high product concentration A. 2 only B. 1 only C. 3 only D. 1 & 2

1 & 2

Which of the following statements about enzymes is/are TRUE? I. Enzymes that require cofactors cannot function without them. II. Enzymes speed up the rate of a reaction by decreasing the ΔG. III. Enzymes are able to catalyze both the forward and reverse reaction. A. 1 only B. 2 only C. 3 only D. 2 & 3 only E. 1 & 3 only F. 1, 2 & 3

1 & 3 only

What are 3 things enzymes do?

1. bind substrate(s) 2. lowers energy of transition state 3. directly promotes catalytic event

What are the 4 significant rate enhancements of enzymes?

1. electrostatic catalysis 2. induced fit 3. binding of substrates to optimize proximity & orientation 4. covalent catalysis

How could you conclusively determine whether a newly discovered enzyme should be classified as a Michaelis-Menten or allosteric enzyme?

1. if substrate(s) is/are known, an enzyme kinetic assay would reveal whether V0 as a function of increasing [S] is hyperbolic vs. sigmoidal 2. solving it's structure to determine whether it has multiple subunits/active sites

Similarities between Michaelis-Menten & Allosteric

1. increase rate of reaction; stabilize transition state 2. interact more favorably w/ transition state than substrates/products 3. can catalyze forwards & reverse reaction 4. specific for specific substrate(s) 5. substrate(s) interact in active site 6. don't alter ΔG or Keq 7. maximum activity at infinite [substrate]; enzyme is saturated

What are some enzyme rate enhancement mechanisms?

1. microenvironment 2. orientation & proximity 3. direct participation in reaction 4. strains reactant bonds(distortion) - enzymes often use more than one strategy to stabilize transition state of reaction

What does rate of a reaction depend on?

1. order of reaction 2. concentrations of reactions & products 3. temperature 4. value of rate constant for reaction

What processes does free energy drive?

1. protein synthesis 2. protein folding 3. transporting ions 4. making ATP(energy)

What are the 3 assumptions of Michaelis-Menten?

1. reverse reaction isn't happening; little to no product is being made 2. concentration of enzyme-substrate is constant 3. maximum rate at saturating concentration of substrate

You are given a biochemical reaction. When will the reaction proceed as written (from left to right)? A. When ΔG = zero. B. When ΔG > zero. C. When ΔG < zero.

When ΔG < zero.

Which of the following statements about metabolism are true? 1. Catabolism is the process in which complex substances are broken down, yielding a net output of energy. 2. Metabolism is an integrated system in which many of the same reactions participate in degradative (catabolic) and biosynthetic (anabolic) pathways. 3. The overall process of metabolism involves the breakdown of polymeric biomolecules and complex lipids to monomers and less complex fats, followed by further degradation to inorganic compounds. 4. All organisms derive raw materials and energy from organic molecules, such as glucose. A. only 1 & 2 are correct B. only 1 & 3 are correct C. only 1,2, 3 are correct D. all four statements are correct

only 1, 2, & 3 are correct

For an unfavorable reaction, the free energy change is _______ and the _______ are favored. A. positive; reactants B. positive; positive C. negative; products D. negative; reactants

positive; reactants

In general, enzymes are what kinds of molecules?

proteins

ΔG equation not in equilibrium

ΔG° + RTln(Q)

ΔG equation

ΔG° + RTln(products/reactants)