Enzyme kinetics #2 Flashcards

1
Q

Lineweaver-Burk plot shows increasing inhibition by…

A

the lines getting flatter/lower

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2
Q

Michaelis-Menten graph shows increasing inhibition by…

A

the lines getting steeper

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3
Q

EI

A

reduces the effective free [E] available for S binding

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4
Q

Competitive inhibition

A

normal graph shows

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5
Q

alpha is

A

a function of [I] - modulations Km

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6
Q

no inhibitor, alpha =

A

1

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7
Q

Lineweaver-Burk plot shows uncompetitive inhibition by…

A

parallel lines

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8
Q

Lineweaver-Burk plot shows non-competitive inhibition by…

A

lines have the same Km so all cross the X axis at the same place

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9
Q

Uncompetitive inhibition

A

~ rare
~ inhibitor can only bind ES complex
~ both Km and Vmax change

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10
Q

Non-competitive inhibition

A

~ inhibitor binds enzyme irrespective of whether substrate is bound or not
~ V max changes
~ Km stays the same

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11
Q

Initial velocity

A

V0
~ function of increasing substrate concentration
~ measured for Michaelis-Menten kinetics

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12
Q

What is plotted in Lineweaver-Burk

A

plotting reciprocals of V0 against [S]

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13
Q

Catalytic efficiency is measured using

A

Vmax and Km

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14
Q

What are the three possible mechanisms for multiple substrates + products (bi-bi)

A

~ ordered
~ random
~ ping-pong

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15
Q

Ordered bi-bi

A

E + A –> EA + B –> EAB –> EPQ –> EQ + P –> E + Q

~ some NAD+/NADP+-requiring enzymes

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16
Q

Random bi-bi

A

~ similar to ordered but A or B can be added first and then P or Q can leave first (no order preference)
~ some dehydrogenases and kinases

17
Q

Ping-pong

A

E + A -> EA-FP –> F + P –> F + B –> FB-EQ –> E + Q

~ chymotrypsin, flavoproteins, transaminases

18
Q

How can bisubtrate mechanisms be differentiated? - PING-PONG

A

~ Lineweaver-Burk

~ double reciprocal plot = parallel lines when altering one substrate conc.

19
Q

How can bisubtrate mechanisms be differentiated? - SEQUENTIAL/ORDERED

A

~ Lineweaver-Burk
~ double reciprocal plot
~ multiple lines have the same Km value
~ random gives similar outcome

20
Q

How do increasing concentrations of substrates/constants in bisubstrtae mechanisms effect the graph?

A

the lines on Lineweaver-Burk become shallower, the more the constant (A or B) increases