behaviour of proteins Flashcards

1
Q

biological catalyst, usually globular proteins

A

enzymes

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2
Q

what is the factor that increase the rate of the enzyme reaction

A

10^20 over an uncatalyzed reaction

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3
Q

it is the difference between energies of reactants and products under standard condition

A

standard free energy, ΔG°

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4
Q

true or false:
enzymes can speed up reactions and can alter the equilibrium constant or the free energy change

A

false - cannot alter

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5
Q

it is the energy input required to initiate a reaction

A

activation energy, ΔG°‡
- reaction rate depends on it

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6
Q

what is the relationship between the temperature of a mixture and the energy available to the reactants to reach the transition state

A

as the temp increase, the energy increase

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7
Q

Description of a reaction whose rate depends on the first power of the concentration of a single reactant

A

first order

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8
Q

Description of a reaction whose rate depends on the product of the concentrations of two reactants

A

second order

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9
Q

Portion of the enzyme surface to which the substrate binds via noncovalent forces (examples) and at which the reaction takes place

A

active site

(hydrogen bonding
electrostatic attractions - glutamic acid and aspartic acid
van der Waals attractions - if non polar)

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10
Q

it is a reactant

A

substrate

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11
Q

substrate binds to that portion of the enzyme with a complementary shape

A

lock and key model

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12
Q

Binding of the substrate induces a change in the conformation of the enzyme that results in a complementary fit

A

induce fit model

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13
Q

what is the difference between lock-and-key model and induce fit model

A

lock-and-key model: no room for flexibility
induce fit model: have room for flexibility

similarities: both gives off product

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14
Q

it has a different three-dimensional shape before the substrate is bound

A

binding site

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15
Q

energy when ES complex bound together

A

lower on energy than at the start

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16
Q

inverse measure of the affinity of the enzyme for the substrate

A

Km, Michaelis constant

17
Q

Substrate binds to the enzyme and releases a product before the second substrate binds to the enzyme

A

Ping-pong mechanism

18
Q

Substrates can bind to the enzyme in any order

A

Random mechanism

19
Q

mM

A

millimoles per liter
1 mM = 1×10–3 mol L–1

20
Q

Substrates have to bind to the enzyme in a specific order

A

Ordered mechanism

21
Q

Number of moles of substrate that react to form product per mole of enzyme per second

A

turnover number
kcat or kp

22
Q

true or false:
increase turnover no, increase enzyme activity

A

True
as turnover no. is the rate on how fast are the changes from the enzyme> substrate > product

23
Q

examples of enzyme-catalyzed reactions and its curve

A

Chymotrypsin - hyperbolic, negative cooperativity
Aspartate -transcarbamoylase (ATCase) - sigmoidal, positive cooperativity

24
Q

Substances that decrease the rate of an enzymecatalyzed reaction

A

inhibitors

25
Q

Reversible inhibitors vs Irreversible inhibitors

A

Reversible inhibitors:
substances that bind to an enzyme and subsequently released

  1. competitive:
    compete the AS
    Vmax: unchanged
    Km: increased
    * it can overcome by high substrate concentration
  2. noncompetitive:
    bind to enzyme other than AS
    Vmax:
    pure - decreased
    mixed - decreased
    Km:
    pure - unchanged
    mixed - decreased
    * lineweaver-burk plot contains parallel lines - Vmax and Km decreases
  3. uncompetitive inhibitors:
    not to the actual enzyme
    Vmax and Km decreases

Irreversible inhibitors:
forms covalent bond to part of AS
permanently preventing substrates from occupying it

26
Q

common table sugar

A

Sucrose - made of glucose and fructose

27
Q

Similar to noncompetitive inhibition but the binding of I does affect the binding of S and vice versa

A

Mixed Noncompetitive Inhibition
*means everything changes, ur Vmax and Km

28
Q

Molecules used to bind to an enzyme irreversibly and inactivate it

A

suicide substrate