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Biochem > Enzymes > Flashcards

Enzymes Flashcards

1
Q

enzymes convert what to products while remaining unchanged themselves?

A

substrates

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2
Q

what are enzymes?

A

catalysts that convert substrates to product while remaining unchanged themselves

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3
Q

what are reacts in enzymes called

A

substrates

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4
Q

Name an enzyme that isnt a protein

A

RNA

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5
Q

What are the 4 main advantages of biocatalysis over inorganic catalysts?

A
  • Greater reaction specificity, so avoids side products
  • milder reaction conditions
  • higher reaction rates
  • capacity for regulation
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6
Q

how are enzymes classified?

A

on the types of reactions that they catalyse

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7
Q

what does lyases do

A

group elimination to form double bonds

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8
Q

what do ligases do

A

bond formation coupled with ATP hydrolysis

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9
Q

what does bromelain do

A

an enzyme that facilitates hydrolysis of proteins

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10
Q

Proteolytic enzymes do what

A

catalyse the hydrolysis of peptide bonds

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11
Q

what type of enzymes illustrate the range of enzyme specificity

A

proteolytic enzymes

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12
Q

enzymes do not alter what

A

The deltaG of a reaction

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13
Q

Free energy is what

A

measure of energy capable of doing work

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14
Q

Change in free energy when a reaction occurs is symbolised by what

A

DeltaG

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15
Q

The more exergonic a reaction, the larger or smaller the equilibrium constant will be?

A

Larger

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16
Q

The more endergonic a reaction, the larger or smaller the equilibrium constant will be?

A

Smaller

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17
Q

the equilibrium constant is directly proportional to what?

A

To DeltaG

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18
Q

Is deltaG positive or negative for an endergonic reaction?

A

Positive

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19
Q

association rate is what?

A

association rate constant x concA x ConcB

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20
Q

dissociation rate is what

A

dissociation rate constant x ConcAB

21
Q

At equilibrium, what is the relationship between association rate and dissociation rate?

A

Association rate = Dissociation rate

22
Q

enzymes increase reaction rates by decreasing what

A

Activation energy

23
Q

what is a transition state

A

A molecular form that is no longer substrate but not yet product

24
Q

What is the activation energy

A

the energy required to form the transition state from the substrate

25
Q

Where does catalysis take place on the enzyme

A

Active site

26
Q

How do enzymes catalyse reactions in terms of transition states

A

They stabilise transition states

27
Q

Enzymes bring substrates together to form what at the active site?

A

form an enzyme-substrate complex at the active site

28
Q

What promotes the formation of the transition state?

A

Interaction of the enzyme and substrates at the active site

29
Q

What is the specificity of the an enzyme due to

A

To the precise interaction of the substrate with the enzyme

30
Q

The active site is what and formed by what

A

is 3D cleft formed by groups that come from different parts of the amino acid sequence

31
Q

how are substrates bound to enzymes (what bonds)

A

multiple weak noncovalent interactions

32
Q

specificity of binding is defined by what

A

3D structures of the active sites and substrates

33
Q

what is excluded from the active site unless it is a reactant?

A

water

34
Q

What character enhances the binding of the substrate as well as catalysis?

A

Non polar character

35
Q

what are the 2 models for the interaction of enzymes with their substrates

A

Lock and Key

Induced Fit Model

36
Q

Hexokinase undergoes what on substrate binding

A

Induced fit

37
Q

What is the energy released upon interaction of the enzyme and substrate?

A

Binding energy is the free energy released

38
Q

When is binding energy the greatest?

A

When the enzyme interacts with the transition state, facilitating the formation of the transition state

39
Q

Binding energy is a major source of free energy used by enzymes to do what

A

lower activation energies of reaction

40
Q

Enzymes being binded to transition states best was proposed by who

A

Linus Pauling 1946

41
Q

Enzyme active sites are what to the transition state of the reaction?

A

complementary

42
Q

Enzymes bind what better than substrates

A

Transition state

43
Q

Describe the binding energy in terms of the stickase exampel

A

Free energy required to draw the stack into the bent shape is offset or paid for by interactions between E and S in the transition state

44
Q

What are inhibitors of enzymes

A

transition state analogs

45
Q

Racemization of proline goes through a transition state in which the alpha carbon is what

A

trigonal

46
Q

Pyrrole 2 carboxylic acid had what geometry

A

Trigonal

47
Q

The similarity between pyrrole 2 carboxylic acid and racemization of proline means that pyrrole 2 carboxylic acid is what

A

Transition state analog and a potent inhibitor of proline racemase

48
Q

Summary of enzymes

A
  • Reactions will proceed only if the free energy difference between reactant (substrate) and product is negative, however the rate may be very slow due to large activation energy required to reach the Transition state.
  • Enzymes lower the activation energy by providing an alternative pathway for the reaction to proceed.
  • Enzymes affect the rate of reaction but not the equilibrium position. They catalyse the forward as well as the reverse reaction
  • Enzymes are not altered in the reaction and can be re-used
  • Enzymes stabilise the transition state. Binding energy offsets the activation energy.
  • Enzymes differ from other catalysts in that they are specific for the substrate. They also work at much milder conditions (pH 7 and 370C)

Biochem (34 decks)

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