Biochemistry- Enzyme Regulation and Inhibition Flashcards

1
Q

What happens to the Km and Vmax Values with competitive inhibition? Where does the inhibitor bind?

A

Raise Km, Vmax= unchanged

binds to free enzyme (E)

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2
Q

Km and Vmax changes upon uncompetitive inhibitor binding. Where does is bind?

A

Decreases Km and Vmax. Binds to the ES complex

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3
Q

Km and Vmax changes after noncompetitive binding. Where does it bind?

A

Decreases Vmax, Km= Unchanged.

Binds to the free enzyme (E) or ES complex

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4
Q

Km and Vmax changes after mixed inhibitor binds. Where does it bind?

A

Increases or decreases Km, decreases Vmax. Binds to either E or ES complex, have a greater affinity for one vs the other, produce conformational changes in enzymes

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5
Q

Michaelis -Menten Equation

A

V0= Vmax [S]/ (Km + [S])

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6
Q

What does Km represent ?

A

michaelis constant, the concentration of the substrate when V0= Vmax/2: substrate concentration at which enzyme-catalyzed reaactions occur at 1/2 their mac velocity

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7
Q

What is the shape of a michaelis-menten kinetics plot?

A

hyperbolic

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8
Q

what does a low Km suggest?

A

the lower the Km, the higher the binding affinity of the enzyme to the substrate.

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9
Q

what is Kcat and how do you determine it?

A

Kcat= turnover number, represents # of substrate molecules converted to product by the enzyme.
formula : Kcat= Vmax/[E]total

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10
Q

what does a large Kcat signify?

A

larger the kcat, the more quickly the enzyme can catalyze the reaction= higher efficiency

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11
Q

kcat/ km ratio

A

the higher the ratio, the higher the efficiency

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12
Q

what is Ic50 and how do you determine it?

A
IC50= half maximal inhibitory concentration
Ki = IC50 / (1 + ([S]/Km))
Ki= substrate concentration
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13
Q

what do points on the lineweaver burke plot represent?

A
  • 1/ Km= x-intercept

1/ Vmax= Y- intercept

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14
Q

Lineweaver burke plot shape for competitive inhibitor

A

3 lines intercept at x intercept and -y intercept ( 1/ Vmax and -1/Km)

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15
Q

Lineweaver burke plot shape for uncompetitive inhibitor

A

All 3 lines are in parallel, do not touch

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16
Q

Lineweaver Burke plot shape for non-competitive inhibitors

A

3 lines intercept 1 x at - y intercept, run parallel through x -axis

17
Q

what is positive cooperativity? Which type of curve does its plot have?

A

binding of one substrate shifts the enzyme from less active form to more active form , making it easier for second substrate to bind. Plot = sigmoidal curve

18
Q

what is an enzyme cofactor?

A

covalently linked to the enzyme, are also called prosthetic groups or ligands

19
Q

What does an oxidoreductase do?

A

catalyzes redox reactions

20
Q

what does a transferase do?

A

transfers groups of atoms

21
Q

what does a hydrolase do?

A

hydrolysis

22
Q

what does a lyase do?

A

bond cleavage by means other than hydrolysis or oxidation to form a new double bond or ring structure

23
Q

isomerase function

A

isomerization of molecules, converts between 2 isomers of a molecule

24
Q

ligases or synthetases function

A

join 2 molecules

25
what are saturation kinetics?
when concentration of substrate is large enough for the substrate to occupy all the available active sites on the enzyme, plot plataeus
26
equilibrium constant formula for calculation
K= [C]^c* [D]^d / [A]^a*[B]^b
27
Equilibrium constant , K, meaning for reaction formation
K>1 , forward reaction favored , products K<1 , reverse reaction favored, reactants K=1, neither forward nor reverse are favored
28
what is catabolism? is it oxidation or reduction?
breakdown of molecules into smaller ones= oxidation
29
what does a lowering of a reaction's Tm ( melting temperature), after adding an enzyme, suggest about the enzyme's affect on molecular stability?
provides conformaitonal stability
30
what conditions are necessary to find the Kcat of a reaction? ( the substrate concentration should be....)
Saturating, Kcat is used to describe the rate-limiting step of catalysis under saturating conditions of substrate
31
phosphatase function
removes phosphate group
32
kinase function, also phosphorylase
attaches phosphate groups