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Bio L6 (1) Biological Molecules > Enzymes > Flashcards

Enzymes Flashcards

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1
Q

What type of biological molecule are enzymes?

A

They are proteins.

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2
Q

What are enzymes?

A

Enzymes are biological catalysts.
They increase the rate of reactions.
Without being chemically used / changed.

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3
Q

Why are enzymes necessary in animals?

A

They catalyse thousands of biochemical reactions every second, (metabolic reactions) that control human processes.

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4
Q

What does the enzyme do to the activation energy required to trigger the reaction?

A

Enzymes lower the activation energy required for a reaction to take place.

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5
Q

Suggest the optimum temperature for enzyme-controlled reactions in humans:

A

37*C. (body temp.)

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6
Q

A significant increase in temp above the optimum temp has an effect on enzyme-controlled reactions.
Explain why this is so:

A
  • Increase causes denaturation due to broken bonds.
  • Changed structure due to loss of 3* structure.
  • Structural change causes functional change (3* = function).
  • No longer catalyse reaction and rate decreases.
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7
Q

State the word that best describes a region on the surface of an enzyme molecule where a substrate can bind.

A

Active site.

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8
Q

State the word that best describes the energy required for a chemical reaction to take place.

A

Activation energy.

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9
Q

What does an oxireductase do?

A

Catalyses redox reactions, through the transfer of hydrogen, oxygen or electrons.

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10
Q

What does a transferase do?

A

Catalyses the transfer of a group from one compound to another, the process of transamination.

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11
Q

What does a hydrolase do?

A

Catalyses hydrolysis and condensation reactions.

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12
Q

What does a lysase do?

A

Catalyses the addition of a group across a double bond.

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13
Q

What does a isomerase do?

A

Catalyses the rearrangements in a molecule to convert isomers.

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14
Q

What does a ligase do?

A

Catalyses bond formation between compounds, using energy from the hydrolysis of ATP.

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15
Q

What is produced when the enzyme lactase is added to milk?

A

Glucose and Galactose.

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16
Q

What contributes to the structure of an enzyme?

A

The sequence of amino acids linked by peptide bonds.

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17
Q

What does an increase in temp do to the movement of molecules?

A

Increases movement.

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18
Q

What does an increase in temp do to the chance of collision between enyzme and substrate?

A

Increases chance of collision.

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19
Q

What term is defined as:

A structural change of a protein that results in the loss of its biological properties.

A

Denaturation.

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20
Q

How does an enzyme speed up the rate of reaction?

A

Provides an alternative reaction pathway with lower activation energy.

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21
Q

When high temps denature a protein, what happens to its structure?

A

The hydrogen bonds and london forces between R groups have been broken leading to a change in the 3* structure.

22
Q

Casein can be used to test enzyme rates of hydrolysis, what feature allows this to be tested?

A

Casein changed colour when digested from an opaque white to clear.

23
Q

Are enzymes globular or fibrous?

A

Globular.

24
Q

What is the main role of enzymes?

A

Catalysing metabolic reactions, he making and breaking of bonds.

25
Q

What does a catalyst do to the ΔH (Enthalpy Change)?

A

Has no effect on ΔH

26
Q

What does a catalyst do the activation energy?

A

Lowers energy required.

27
Q

What are the two theories of enzyme action?

A
  • Lock and key mechanism.

- Induced fit hypothesis.

28
Q

What is the lock and key hypothesis?

A
  • The shape and charge of the substrate are complimentary to the active site.
  • They collide and bind to form an enzyme-substrate complex (e.s.c).
  • Products released, freeing the active site for the next reaction.
29
Q

What is the induced fit hypothesis?

A
  • The collision between substrate and active site changes the shape of the enzyme slightly.
  • This creates strain on enzyme structure creating stored energy.
  • The recoil of the enzyme puts strain on the substrate, forming/breaking bonds.
  • Products released no longer fit the A.S.
30
Q

Name some factors that affect enzyme activity:

A
  • Temperature;
  • pH;
  • Enzyme / Substrate concentration;
  • Inhibitors;
  • Co-factors or prosthetic groups.
31
Q

What is Q10?

A

The factor which rate of reaction increases for every 10*C rise in temp.

32
Q

What is the Q10 equation?

A

Rt x Q10 = Rt + 10

33
Q

Why does the stomach have a low pH?

A

To kill bacteria in food.

34
Q

Do all enzymes have the same optimum pH?

A

No they are all different.

35
Q

Explain the effects of increasing conc^ of substrate on frequency of collisions.

A
  • Increasing conc^ increases the frequency of collisions as there are more substrates per area.
  • Until all active sites are occupied.
  • Then further increases have no effect on the frequency of collisions as they are not thee limiting factor.
36
Q

What is Vmax?

A

The maximum rate of reaction.

37
Q

How is Km found?

A

Half Vmax.

38
Q

What is Km?

A

The conc^ of substrate required to achieve half of Vmax.

39
Q

Explain the effect of increasing enzyme conc^ on rate of reaction.

A

Increased enzyme conc^ means more A.S available, more A.S means more collisions, this leads to more ESC formed.

40
Q

What are the two types of inhibition?

A

Competitive and Non-competitive.

41
Q

How does non-competitive inhibition work?

A
  • The inhibitor does not bind to the active site, it binds to another part of the enzyme, the allosteric site.
  • This changes the tertiary structure as the shape of the A.S is altered.
  • Fewer ESC can be formed.
42
Q

What is the allosteric site?

A

Where non-competitive inhibitors bind.

43
Q

Explain competitive inhibition:

A
  • The inhibitor fits into the active site.
  • This forms an enzyme-inhibitor complex (EIC)
  • This means the active site is in use and therefore, no ESC’s can be formed.
44
Q

What is end product inhibition used for?

A

Controlling metabolic rates.

45
Q

When an inhibitor is bound to the allosteric site, what happens to the active site:

A

The shape is changed and therefore cannot form ESC’s.

46
Q

What is an EIC?

A

Enzyme-Inhibitor Complex

47
Q

What is an ESC?

A

Enzyme-Substrate Complex

48
Q

What is a prosthetic group an example of?

A

A coenzyme.

49
Q

In enzyme experiments, the rate of enzyme activity often gradually decreases. What is most likely to cause this decrease?

A

The substrate concentration decreases.

50
Q

What volume of solution is needed to make 15cm^3 of 0.3M lactose solution from a 1.5M stock solution?

A

3cm^3

51
Q

Why would we use an initial rate of reaction?

A

To show maximum rate with no limiting factors.

52
Q

Describe the induced-fit model of enzyme action.

A
  • Before the reaction, active site is not complimentary to substrate.
  • The shape of active site changes as substrate binds to the active site.
  • Enzyme-substrate complex forms.
  • Distortion of bonds in substrate leads to reaction.

Bio L6 (1) Biological Molecules (13 decks)

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