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CHEM 472 Biochem > Exam 2: Chp 13 > Flashcards

Exam 2: Chp 13 Flashcards

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1
Q

What are enzymes?

A

Proteins specialized to catalyze metabolic reactions by changing kinetics

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2
Q

What is catalytic power?

A

The ratio of enzyme-catalyze rate to uncatalyzed rate

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3
Q

What is specificity of a molecule?

A

it is selective for substrate, product, or type of reaction

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4
Q

What is regulation of enzymes?

A

the rate controlled to meet cellular requirements

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5
Q

On what two levels is regulation performed?

A

production/genetic level and binding interaction by inhibitors or activators

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6
Q

What type of reactions do oxidoreductase enzymes catalyze?

A

redox reactions

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7
Q

What type of reactions do transferase enzymes catalyze?

A

transfer functional groups

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8
Q

What type of reactions do hydrolase enzymes catalyze?

A

hydrolysis

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9
Q

What type of reactions do lyase enzymes catalyze?

A

bond cleavage not via redox or hydrolysis

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10
Q

What type of reactions do isomerase enzymes catalyze?

A

isomerization

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11
Q

What type of reactions do ligase enzymes catalyze?

A

bond formation with the help of ATP

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12
Q

What type of reactions do translocate enzymes catalyze?

A

molecule or ion movement across a membrane

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13
Q

What is an enzyme cofactor? Examples?

A

An inorganic component that allows chemistry AAs cannot perform alone; metal ions, Na+, Ca+

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14
Q

What is a coenzyme/prosthetic group?

A

A small organic fragment covalently or non-covalently associated with an enzyme

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15
Q

What is an holoenzyme?

A

A complex of protein and cofactor or coenzyme

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16
Q

What is an apoenzyme?

A

A protein without its specific cofactor or coenzyme; typically inactice

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17
Q

How does temperature affect reaction rate?

A

Reaction rate increases as temperature does

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18
Q

How do catalysts affect reaction rate?

A

Stabilizes the transition state which lowers activation energy, speeding up the reaction

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19
Q

What is the lock and key model?

A

The substrate molecular structure is complementary to the enzyme structure which create specificity

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20
Q

What is the induced fit model?

A

As the substrate binds the active site and substrate change confirmation and become complimentary

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21
Q

Why is the induced fit model beneficial?

A

Explains catalytic activity and specificity

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22
Q

Where does the energy for confirmation changes during substrate and enzyme binding come from?

A

Formation of stabilizing non-covalent interactions between enzyme and substrate

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23
Q

What is Vmax?

A

The maximum reaction rate of an enzyme-substrate complex

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24
Q

When does Vmax occur?

A

when all enzyme is occupied by substrate

25
Q

What is steady state assumption kinetics?

A

Assume ES is constant in E+ S → ES → E + P is nonreversible

26
Q

What is Km and what does is measure?

A

It is 1/2 of Vmax and is a measure of binding affinity between substrate and enzyme

27
Q

What is Kcat?

A

A measure of catalytic efficiency

28
Q

What does a low Km mean?

A

Strong binding affinity

29
Q

What does a high Kcat mean?

A

High catalytic efficiency

30
Q

What is the x-intercept of a Lineweaver-Burke plot equal to?

A

-1/km

31
Q

What is the slope of a Lineweaver-Burke plot equal to?

A

Km/Vmax

32
Q

What is the y-intercept of Lineweaver Burke plot equal to?

A

1/Vmax

33
Q

What are two factors that influence enzyme kinematics?

A

pH and temperature

34
Q

How does pH influence enzyme kinetics?

A

Enzymes have a standard distribution surrounding their optimal pH because pH influences their protonation, thus overall structure

35
Q

How does temperature influence enzyme kinetics?

A

Most enzyme activity increases rate up to 50-60°C then denature

36
Q

What are enzyme inhibitors?

A

Small molecules that bind to the enzyme and either slow or completely inhibit the catalytic process

37
Q

What are the two general kinds of inhibitors?

A

Reversible and Irreversible

38
Q

Why are reversible inhibitors able to be removed?

A

They bind via non-covalent interactions

39
Q

What are the four kinds of reversible inhibitors?

A

Competitive, Noncompetitive uncompetitive, and mixed

40
Q

How does a competitive inhibitor interact with the enzyme and substrate?

A

Competes with substrate to bind to active site

41
Q

How does concentration affect competitve inhibition?

A

Binding favors that in higher concentration

42
Q

How does a competitive inhibitor affect the y-intercept of a Lineweaver-Burke plot of an enzyme?

A

Vmax stays the same because it assumes high substrate concentration → y-intercept does not change

43
Q

How does a competitive inhibitor affect the x-intercept of a Lineweaver-Burke plot of an enzyme?

A

Km increases because more substrate is needed to reach Vmax → x-intercept decrease

44
Q

How does a noncompetitive inhibitor interact with an enzyme and its substrate?

A

The inhibitor binds to a site distinct from the active site and does not affect substrate binding, but prevents catalytic activity

45
Q

How does a non-competitive inhibitor affect the y-intercept of a Lineweaver-Burke plot of an enzyme?

A

Vmax decreases because no turnover → y-intercept increases

46
Q

How does a non-competitive inhibitor affect the x-intercept of a Lineweaver-Burke plot of an enzyme?

A

Km stays the same because substrate binding is unaffected→ x-intercept remains unchanged

47
Q

How does a uncompetitive inhibitor interact with an enzyme and its substrate?

A

Inhibitor binds to the enzyme-substrate complex and inhibits catalytic activity

48
Q

How does a uncompetitive inhibitor affect the y-intercept of a Lineweaver-Burke plot of an enzyme?

A

Vmax decreases because substrate cannot compete with inhibitor → y-intercept increases

49
Q

How does a uncompetitive inhibitor affect the x-intercept of a Lineweaver-Burke plot of an enzyme?

A

Km decreases because more inhibitor complex shifts the equilibrium → x-intercept increases

50
Q

How does a mixed inhibitor interact with an enzyme and its substrate?

A

inhibitor binding to the enzyme makes it harder for substrate to bind

51
Q

What are two kinds of mixed inhibition?

A

1) inhibitor favors binding E on its own
2) inhibitor favors binding to enzyme substrate complex

52
Q

In mixed inhibition where lone enzyme is favored, how is the y-intercept of a Lineweaver-Burke plot of an enzyme affected?

A

Vmax stays the same → y-intercept stays the same

53
Q

In mixed inhibition where lone enzyme is favored, how is the x-intercept of a Lineweaver-Burke plot of an enzyme affected?

A

Km increases because more substrate is needed to reach Vmax → x-intercept decreased

54
Q

In mixed inhibition where enzyme-substrate complex is favored, how is the y-intercept of a Lineweaver-Burke plot of an enzyme affected?

A

Vmax is decreased → y-intercept increased

55
Q

In mixed inhibition where enzyme-substrate complex is favored, how is the x-intercept of a Lineweaver-Burke plot of an enzyme affected?

A

Km is decreased → x-intercept is increased

56
Q

How does an irreversible inhibitor affect Vmax and Km?

A

Km remains the same and Vmax is decreased

57
Q

Why can irreversible inhibitors not be removed?

A

They follow the enzyme catalytic process but form covalent intermediate

58
Q

What is the chemical function of penicillin?

A

prevents crosslinking of peptidoglycan in bacterial cell walls by inhibiting transpeptidase

59
Q

How and why does penicillin inhibit transpeptidase?

A

Mimics D-Ala-D-Ala pattern of normal substrate that irreversibly binds to serine

CHEM 472 Biochem (12 decks)

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