Enzyme and Kinetics Flashcards by Cathrina Chavez

What is a competitive inhibitor of an enzyme usually?
a. a highly reactive compound
b. a metal ion such as Hg2+ or Pb2+
c. structurally similar to the substrate.
d. water insoluble

structurally similar to the substrate

Competitive inhibitors often resemble the substrate and compete for binding at the active site.

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Linear inhibition is sometimes called as?
a. complete inhibition
b. incomplete inhibition
c. partial inhibition
d. mixed inhibition

complete inhibition

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What are the types of inhibition pattern based on the Michaelis Menten equation?

a. competitive
b. non-competitive
c. uncompetitive
d. all of the above

all of the above

These types of inhibition describe how different inhibitors affect enzyme kinetics.

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The effect of non-competitive inhibition on a Lineweaver-Burk Plot is that?
a. it can move the entire curve to the right
b. it can change the y-intercept
c. it can change the x-intercept
d. all of these

it can change the y-intercept

Non-competitive inhibition affects the maximum reaction rate without altering the binding affinity.

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The rate-determining step of Michaelis Menten kinetics is?
a. the complex formation step
b. the complex dissociation step to produce
product
c. the product formation step
d. Both (a)and(c)

the complex dissociation step to produce product

This step is critical in determining the overall rate of the enzymatic reaction.

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In competitive inhibition, a factor is obtained from the measurement of?
a. Vmax
b. KM
c. Y-intercept in Lineweaver-Burk Plot
d. None of these

KM reflects the substrate concentration at which the reaction velocity is half of Vmax.

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Which of these proteases is not a cysteine active site protease?
a. Calpain
b. Cathepsin D
c. Papain
d. None of the above

Cathepsin D

Cathepsin D is classified differently and does not have a cysteine active site.

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Given an enzyme with a Km = 10mM and Vmax = 100 m mol/min, if [S] = 100 mM, which of the following will be true?

a. A 10-fold increase in Vmax would increase
velocity 10-fold y
b. A 10-fold decrease in Km would increase
velocity
c. Both (a) and (b)
d. A 10-fold increase in Vmax would decrease
velocity 20-fold

A 10-fold increase in Vmax would increase
velocity 10-fold y

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The conformational change in an enzyme after the substrate is bound can be explained by?

a. induced fit
b. transition
c. fit and fine
d. Pasteur

induced fit

Induced fit describes how enzymes adjust their shape to better accommodate the substrate.

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The active site of an enzyme remains?
a. at the center of globular proteins
b. rigid and does not change shape
c. complementary to the rest of the molecule
d. none of the above

none of the above

The active site can be flexible and is not always rigid.

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Which category of enzymes belongs to class two in the international classification?
a. Hydrolases
b. Ligases
c. Transferases
d. Isomerase

Transferases

Transferases are enzymes that catalyze the transfer of functional groups.

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The Woolf-Augusteinsson-Hofstee plot is considered more reliable when the error in v is?
a. non-significant
b. significant
c. nothing to do with the reliability
d. non-significant in selected cases

significant

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The relationship between Keq, Km and Vmax is known as?
a. Haldane equation
b. Michaelis Menten equation
c. Numerical solution approach
d. Gibbs-Helmholtz equation

Haldane equation

The Haldane equation relates equilibrium constants to enzyme kinetics.

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The reciprocal equation for non-competitive inhibition can be arranged to the equation for the?
a. Dixon plot
b. Woolf-Augusteinsson-Hofstee plot
c. Eadie-Scatchard plot
d. Hanes-Woolf plot

Dixon plot

This plot format helps visualize the effects of non-competitive inhibitors.

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Which of the following statements is true for enzymatically catalyzed reactions?

a. The activation energy of the reaction is
lowered so that a larger proportion of the
substrate qualifies to overcome it

b. Additional substrate molecules are
energized to overcome the activation
energy of the reaction

c. The activation energy of the reaction is
increased, thus decreasing the likelihood
that any substrate molecules will overcome
it

d. The activation energy of the reaction is
lowered so that fewer substrate molecules
can overcome it

The activation energy of the reaction is lowered so that a larger proportion of the substrate qualifies to overcome it

Enzymes facilitate reactions by lowering the activation energy barrier.

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Which of the following common drugs is not a specific enzyme inhibitor?
a. Iodine
b. Methotrexate
c. Sulfanilamide
d. Penicillin

Iodine

Iodine does not specifically inhibit enzyme activity like the other options listed.

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In a Lineweaver-Burk Plot, a competitive inhibitor shows which of the following effect?

a. It moves the entire curve to right
b. It moves the entire curve to left
c. It changes the x-intercept
d. It has no effect on the slope

It changes the x-intercept

Competitive inhibitors affect how the substrate interacts with the enzyme, altering the x-intercept.

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Which of the following statements is not true?

a. Enzymes are proteins that bind to specific
substrates and increase the velocity of
reactions involving those substrates

b. Enzymes function by overcoming the
activation energy barrier of a reaction

c. Enzymes make thermodynamically
favorable reactions to proceed; they cannot
make unfavorable reactions to occur

d. Enzymes only function when they are in
intact cells

Enzymes only function when they are in intact cells

Enzymes can function outside of cells in vitro as well.

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An enzyme and a reactant molecule maintain a relationship as?

a. a temporary association
b. an association stabilized by a covalent bond
c. one in which the enzyme is changed
permanently
d. non complementary binding

a temporary association

The binding between an enzyme and substrate is typically transient.

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An enzyme is assayed at an initial substrate concentration of 2 x 10^-5M. In 6 minutes, half of the substrate is used. The Km for the substrate is 2 x 10^-3M. The value of k in minute is?

a. 0.115
b. 0.42
c. 0.093
d. 6.693

0.115

This reflects the rate constant derived from the substrate usage over time.

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The plot commonly used for determining the value of Vmax is?

a. Lineweaver Burk plot
b. Langmuir plot
c. Eadie Hofstee plot
d. all of these

all of these

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Quasi steady state is also known as?

a. Michaelis Menten approach
b. Briggs-Haldane approach
c. Pseudo steady state
d. all of the above

Pseudo steady state

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A noncompetitive inhibitor of an enzyme-catalyzed reaction?

a. increases KM and increases Vmax
b. increases KM and reduces Vmax
c. reduces KM and increases Vmax
d. reduces KM and reduces Vmax

increases KM and reduces Vmax

Noncompetitive inhibitors affect the rate but not the affinity of the enzyme for the substrate.

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An allosteric inhibitor of an enzyme usually?
a. participates in feedback regulation
b. denatures the enzyme
c. is a hydrophobic compound
d. causes the enzyme to work faster

participates in feedback regulation

Allosteric inhibitors can regulate enzyme activity through conformational changes.

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A classical uncompetitive inhibitor is a compound that binds? a. reversibly to the enzyme substrate complex yielding an inactive ESI complex b. irreversibly to the enzyme substrate complex yielding an inactive ESI complex c. reversibly to the enzyme substrate complex yielding an active ESI complex d. irreversibly to the enzyme substrate complex yielding an active ESI complex

reversibly to the enzyme substrate complex yielding an inactive ESI complex ## Footnote Uncompetitive inhibitors bind only to the enzyme-substrate complex, not the free enzyme.

Which graphical method is used to determine an enzyme degree of **cooperativity**? a. Hill plot b. Koshland curve c. Michaelis-Menten hyperbola d. Can not be determined

Hill plot ## Footnote The Hill plot is used to assess the cooperative binding of substrates to enzymes.

The ratio of the amount of a protein present in a sample, which is used as a measure of purification, is known as? a. specific activity b. relative activity c. purity ratio d. all of these

specific activity ## Footnote Specific activity quantifies enzyme activity relative to the amount of protein present.

If a reaction occurs in the absence of inhibitor with rate ν0 and in the presence of inhibitor with rate νi, the degree of inhibition is defined as? a. (ν0 - νi)/ν0 b. (ν0 + νi)/ν0 c. (ν0νi)/ν0 d. (ν0-νi)/νi

(ν0 - νi)/ν0 ## Footnote This formula quantifies the effectiveness of the inhibitor on the enzymatic reaction.

The rate equation in competitive inhibition based on Michaelis Menten equation is given by? a. rmaxS/(Km(1+I/Ki) +S)) b. rmaxE/(Km(1+I/Ki) +S)) c. rmaxI/(Km(1+I/Ki) +S)) d. rmaxS/(Km(1+I/Ki))

rmaxS/(Km(1+I/Ki) +S) ## Footnote This equation illustrates how competitive inhibition alters the rate of reaction.

**Classical noncompetitive inhibition** is obtained only under? a. slow equilibrium conditions b. moderate equilibrium conditions c. rapid equilibrium conditions d. non-equilibrium conditions

rapid equilibrium conditions ## Footnote Noncompetitive inhibition assumes a rapid equilibrium between enzyme and inhibitor.

In the steady state, the material balance equation for any component of a system is? a. rate of addition + rate of removal - rate of formation = 0 b. rate of addition - rate of removal + rate of formation = 0 c. rate of addition + rate of removal + rate of formation = 0 d. none of the above

rate of addition - rate of removal + rate of formation = 0 ## Footnote This equation describes the conservation of mass in a dynamic system.

For an enzyme that displays Michaelis-Menten kinetics, the reaction velocity (as a fraction of Vmax) observed at [S] = 2 KM will be?

0.66 ## Footnote At this substrate concentration, the reaction velocity approaches Vmax.

Predominantly uncompetitive inhibition may be called when? a. competitive inhibition is greater than uncompetitive inhibition b. competitive inhibition is smaller than uncompetitive inhibition c. competitive inhibition is equal to uncompetitive inhibition d. none of the above

competitive inhibition is smaller than uncompetitive inhibition ## Footnote This describes a scenario where uncompetitive inhibition is the dominant form of inhibition.

An enzyme has a Km of 4.7 x 10^-5M. If the Vmax of the preparation is 22m moles liter-1 min-1, what velocity would be observed in the presence of 2.0 x 10^-4M substrate and 5.0 x 10^-5M of a competitive inhibitor? a. 13.54μ moles liter-1min-1 b. 6.68μ moles liter-1min-1 c. 7.57μ moles liter-1min-1 d. 17.8μ moles liter-1min-1

13.54μ moles liter-1min-1 ## Footnote This calculation reflects the influence of substrate and inhibitor concentrations on enzyme activity.

The rate equation in non-competitive inhibition based on Michaelis Menten equation is given by? a. rmaxS/ (Km + S) (1+I/Ki) b. rmaxE/ (Km (1+I/Ki) +S)) c. VmaxS/ (Km + S) (1+I/Ki) d. rmaxS/Km

rmaxS/ (Km + S) (1+I/Ki) ## Footnote This reflects how non-competitive inhibitors affect reaction rates.

Which of the following statement(s) regarding enzymes is/are false? a. Enzymes are always proteins that function as catalysts b. Enzymes provide activation energy for reactions c. Enzyme activity can be regulated d. Enzymes may be used many times for a specific reaction

Enzymes provide activation energy for reactions ## Footnote Enzymes do not provide energy; they lower the activation energy barrier.

The slope of Lineweaver Burk plot for Michaelis Menten equation is? a. Vmax/Km b. Km/Vmax c. 1/Km d. Km*Vmax

Km/Vmax ## Footnote The slope of this plot provides insight into enzyme kinetics.

The initial velocity, V0, of an enzyme-catalyzed reaction **reaches** Vmax as? a. [S] = KM b. [S] = 10 * KM c. 1/[S] = 1/KM d. 1/[S] → 0

1/[S] → 0 ## Footnote This condition indicates that all enzyme active sites are occupied.

The usual method(s) to solve rate equation of simple enzyme kinetics is/are? a. Michaelis Menten approach b. Briggs-Haldane approach c. Numerical solution approach d. all of these

all of these ## Footnote Various approaches can be employed to analyze enzyme kinetics.

Michaelis Menten equation can also be written as? a. (-Cs)/r = (Cs/rmax)+(Km/rmax) b. 1/r = (1/rmax)+(Km/(rmax.Cs)) c. r = rmax-(Km.r/Cs) d. All of these

All of these ## Footnote The equation can be expressed in different forms depending on the context of the analysis.

Which of the following step is assumed to be the **slowest step** in the Michaelis Menten equation? a. The substrate consuming step b. The product releasing step c. Formation of enzyme substrate complex d. None of these

The product releasing step ## Footnote This step often determines the overall reaction rate.

When **substrate [S] = KM**, the velocity of an enzyme-catalyzed reaction is about? a. 0.1 * Vmax b. 0.2 * Vmax c. 0.5 * Vmax d. 0.9 * Vmax

0.5 * Vmax ## Footnote This indicates that at KM, the reaction is at half its maximum velocity.

A classical **noncompetitive** inhibitor has? a. no **effect** on substrate binding b. no **effect** on substrate binding and vice versa c. significant **effect** on substrate binding d. significant **effect** on substrate binding and vice versa

no effect on substrate binding ## Footnote Noncompetitive inhibitors do not affect how the substrate binds to the enzyme.

The active site of an enzyme differs from an antibody-antigen binding site in that the enzyme active site? a. contains modified amino acids b. catalyzes a chemical reaction c. is complementary to a specific ligand d. contains amino acids without side chains

catalyzes a chemical reaction ## Footnote Enzyme active sites are specifically designed to facilitate chemical transformations.

Enzymes are basically? a. Proteins b. Vitamins c. Fat d. Carbohydrates

Proteins ## Footnote Enzymes are predominantly proteins that function as biological catalysts.

Which of the following refers to pseudo steady state? a. d(CE)/dt = 0 b. d(Cp)/dt = 0 c. d(CES)/dt = 0 d. d(Cs)/dt = d(CES)/dt

d(CES)/dt = 0 ## Footnote Pseudo steady state indicates that the concentration of the enzyme-substrate complex remains constant over time.

Most enzymes work by? a. increasing energy of activation b. decreasing energy of activation c. not affecting energy of activation d. none of the above

decreasing energy of activation ## Footnote Enzymes facilitate reactions by reducing the energy required for the reaction to occur.

Which category of enzymes belongs to **class 5** in the **international** classification? a. Hydrolases b. Isomerases c. Oxido-reductases d. Cyclase

Isomerases ## Footnote Isomerases catalyze the rearrangement of molecular structures.

Lock and key theory is based on the compatibility of? a. enzyme and substrate b. enzyme and product c. enzyme and enzyme substrate complex d. enzyme substrate complex and product

enzyme and substrate ## Footnote This theory suggests that the enzyme's active site is complementary to the substrate.

When an enzyme is functioning at Vmax, the rate of the reaction is limited by? a. the number of collisions between enzyme and substrate b. the number of substrate molecules in the reaction c. the concentration of the substrate d. the rate at which the enzyme can convert substrate to product

the rate at which the enzyme can convert substrate to product ## Footnote At Vmax, all active sites are occupied, and the reaction rate is at its maximum.

The equation for the rate of product formation for simple enzyme reaction is given by? a. rp = rmax Cs/(Km+Cs) b. rp= rmax CES/ (Km+ CES) c. rp = rmax Cs/(Km+CES) d. rp = rmax Cs/(Km+Cp)

rp = rmax Cs/(Km+Cs) ## Footnote This equation describes how product formation depends on substrate concentration.

When **[S] = 0.1 KM**, the velocity of an enzyme-catalyzed reaction is about? a. 0.1 * Vmax b. 0.3 * Vmax c. 0.5 * Vmax d. 0.7 * Vmax

0.1 * Vmax ## Footnote This reflects the reaction velocity at a low substrate concentration.

Juice clarification extraction is facilitated by using? a. Cellulases b. Amylase c. Inulinase d. Lactase

Cellulases ## Footnote Amylase helps to break down starches and clarify juice.

Lysozyme is naturally present in? a. egg white b. bacteria c. tears & milk d. all of these

all of these ## Footnote Lysozyme can be found in various biological fluids and tissues.

Enzymes act as antimicrobials? a. by depriving an organism of a necessary metabolite b. by generating a substances toxic to the organism c. by attracting a cell wall component d. all of the above

all of the above ## Footnote Enzymes can inhibit microbial growth through various mechanisms.

Trichoderma β-glucanase is reported? a. to stabilize mashing b. to convert taste fractions of dextrins to fermentable sugars in beer c. to convert starch to dextrin d. all of the above

to stabilize mashing ## Footnote This enzyme has multiple applications in brewing and food processing.

The bitter taste of the high **protein** materials is reduced by using? a. Invertase b. Dectinase c. Protease d. none of these

Protease ## Footnote Proteases can break down proteins that contribute to bitterness.

Sulphydryl oxidase is used for? a. Discoloration b. clarification of images c. UHT milk off flavor removal d. all of these

UHT milk off flavor removal ## Footnote This enzyme has various applications in food processing and preservation.

α-amylase is an endo enzyme which requires? a. Ca b. Cu c. Mn d. None of these

Ca ## Footnote Calcium is a cofactor necessary for the activity of α-amylase.

Liquefaction of starch to dextrin is carried out by? a. α-amylase b. cellulase c. pectinase d. all of these

α-amylase ## Footnote α-amylase catalyzes the breakdown of starch into shorter sugar chains.

**Milk digestibility** is improved by using? a. RNase b. Lactase c. β-amylase d. none of these

Lactase ## Footnote Lactase helps in the digestion of lactose, improving digestibility for lactose-intolerant individuals.

Which of the following mainly serve to convert starch into high fructose corn syrup (HFCS)? a. α-amylase b. Gluco-isomerase c. Gluco-amylase d. all of these

all of these ## Footnote All listed enzymes play a role in the conversion process.

Lysozyme a. catalyses hydrolysis of β-1-4 linkages between N-acetyl muranic acid and N acetyl glucosamine in peptideoglycan b. catalyses hydrolysis of α-1-4 linkages between N-acetyl muranic acid and N acetyl glucosamine in peptideoglycan c. catalyses hydrolysis of α-1-4 linkages between N-diacetyl muranic acid and N diacetyl glucosamine in peptideoglycan d. all of the above

β-1-4 linkages between N-acetyl muranic acid and N-acetyl glucosamine in peptideoglycan ## Footnote This reaction is crucial for breaking down bacterial cell walls.

Hersperidinase is used for? a. juice clarification b. juice debittering c. off flavour reduction d. RNA reduction in fish

juice clarification ## Footnote Hersperidinase helps to reduce bitterness in juice products.

Which of the following metallic ion is there in ascorbic acid oxidase? a. Mg b. Fe c. Cu d. Mn

Cu ## Footnote Copper is a cofactor for ascorbic acid oxidase, aiding its enzymatic function.

Which of the enzyme combination is commercially used for the removal of oxygen? a. Glucose oxidase-cellulase b. Glucose oxidase-catalase c. Glucose oxidase-lactase d. All of these

Glucose oxidase-catalase ## Footnote This combination is effective for oxygen removal in various applications.

**Citrus juice bittering** can be carried out using which enzyme? a. Limoninase b. Inulinase c. Anthocyanase d. None of these

Limoninase ## Footnote Limoninase specifically targets compounds that cause bitterness in citrus fruits.

Which enzyme is responsible for causing **vitamin B** deficiency disease beriberi? a. Ascorbic acid oxidase b. Thiaminase c. Lipoxygenase d. None of these

Thiaminase ## Footnote Thiaminase breaks down thiamine, leading to deficiency.

Soya off flavour removal may be achieved using a. di acetyl reductase b. β- amylase c. aldehyde oxidase d. protease

aldehyde oxidase ## Footnote This enzyme helps in reducing off-flavors in soy products.

The **reduction in off flavour of beer** is practiced through which enzyme? a. Hersperidinase b. Rnase c. Invertase d. diacetyl reductase

diacetyl reductase ## Footnote This enzyme is important for improving the flavor profile of beer.

Discoloration can be achieved by using a. sulphloydryl oxidase b. proteases c. anthocyanase d. all of these

anthocyanase

The prosthetic group present in phenolase enzyme is a. Mg b. Cu c. Ca

Cu ## Footnote Copper acts as a cofactor essential for phenolase activity.

Enzymes degrade, alter or synthesize a food component through a. oxidation/reduction/isomerization b. hydrolysis/synthesis c. group transfer d. all of the above

all of the above ## Footnote This includes various biochemical processes like oxidation, hydrolysis, and group transfer.

The enzyme β-**galactos**idase is also known as a. Lactase b. EC3.2.1.23 c. both (a) and (b) d. isomerase

isomerase

Chymosin hydrolyses the bond between a. Alanine and glycine b. Phenyl alanine and methionine c. Glutamic acid and alanine d. Alanine and phenyl alanine

Phenyl alanine and methionine