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Green > 2.1.4: Enzymes > Flashcards

2.1.4: Enzymes Flashcards

1
Q

Define what an enzyme is

A
  • Biological catalyst
  • A protein that speeds up the rate of reaction in a living organism without being used up
  • Lowers activation energy
  • Provides an alternative reaction pathway
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2
Q

What is the structure of an enzyme?

A

Globular protein

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3
Q

What can an enzyme effect in an organism ?

A

Structure ,function and metabolism of a whole organism

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4
Q

Why are enzymes (biological catalysts) better than chemical catalysts ?

A

No side reactions and high turnover rate

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5
Q

How far do enzymes increase the rate of reaction up to ?

A

Up to the Vmax

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6
Q

What type of enzyme is amylase ?

A

Extracellular

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7
Q

Where can amylase be found ?

A
  • Salivary glands
  • Small intestine
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8
Q

What are extracellular enzymes ?

A
  • Nutrients present in diet or environment of organism which are often large polymers e.g. large proteins
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9
Q

What are the function of extracellular enzymes ?

A

Enzymes released to break nutrients down

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10
Q

What is the function of amylase ?

A

Catalyses the digestion for the hydrolysis of starch so it is small enough to be absorbed by the digestive system lining in the bloodstream

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11
Q

What is the function of trypsin ?

A

Catalyses the breakdown of protein into smaller peptides and amino acids which are small enough to be absorbed by the digestive system lining in the bloodstream

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12
Q

What type of enzyme is trypsin ?

A

Extracellular

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13
Q

Where is the enzyme trypsin found ?

A

Produced in the pancreas then released into the small intestine via pancreatic juice

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14
Q

Give the 4 types of reactions that enzymes catalyse ?

A
  • Intracellular
  • Extracellular
  • Condensation
  • Hydrolysis
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15
Q

What type of enzyme is catalase ?

A

Intracellular

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16
Q

Give the reaction for the breakdown of hydrogen peroxide by catalase

A

H202 (l) –> 2H20 + O2

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17
Q

Whats the benefit of using an enzyme to catalyse the breakdown of hydrogen peroxide ?

A

Highest turnover rate as H202 is toxic so needs to be broken down in liver cells quickly so it doesn’t damage

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18
Q

Give the steps for the breakdown of starch

A

Starch broken down by amylase into maltose –> maltose broken down by maltase into glucose which is small enough to be absorbed into the bloodstream

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19
Q

What is special about an active site and why is it special ?

A

Specific shape due to specific folding and bonding in the tertiary structure of the protein

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20
Q

Explain the lock and key hypothesis

A
  • Due to enzymes specific tertiary structure it results in an active site which is complementary to the substrate
  • Active site is a fixed shape
  • Substrate binds to complementary active site forming an ESC
  • Substrate is broken down into products
  • Products are released and enzyme is unchanged
  • Charged groups within active site distort substrate to lower activation energy and energy to break substrate bonds
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21
Q

Explain the induced fit hypothesis

A
  • Enzyme active site is induced to change shape so it is complementary to substrate when it collides
  • When the ESC forms, strain is put on the bonds within the substrate as many weak enzyme and substrate interactions which lowers activation energy
  • Products are released from the enzyme
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22
Q

Why is the initial rate of reaction always the highest ?

A
  • Maximum concentrations of substrates
  • Maximum number of available active sites
  • More successful enzyme and substrate collisions
  • More ESCs form
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23
Q

Give 2 reasons why ESCs forming lowers activation energy

A
  • Special chemical conditions on active site
  • Reactants are held together in exposed conditions
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24
Q

How does a higher temperature effect enzyme activity ?

A
  • Molecules have more kinetic energy ( substrate and enzyme )
  • More successful collisions with more force
  • More ESCs form
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25
Q

What happens if the temperature is too high for an enzyme (above optimum) ?

A

Enzymes denature as bonds break in the tertiary structure ( ionic + hydrogen ) causing a change to the shape of the active site so it is no longer complementary to the substrate .ESCs can’t form and rate decreases

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26
Q

What specifically breaks the bonds within an enzyme when it denatures ?

A

Kinetic energy/ vibrations between R groups

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27
Q

What happens if pH is too low or high to an enzyme ?

A

pH interferes with charges in amino acid in active site which breaks ionic/hydrogen bonds .Enzyme denatures as tertiary structure is altered which changes the shape of the active site and makes it no longer complementary

28
Q

Give the Q10 equation

A 
rate at t degrees lower temp
29
Q

What does the Q10 equation measure ?

A

The rate of change of reaction by increasing the temperature by 10 degrees

30
Q

How does a high substrate concentration effect the rate of reaction ?

A

Rate plateaus as all the enzyme active sites are in use (are saturated)

31
Q

How does a low concentration of substrate effect the rate of reaction ?

A
  • Fewer collision
  • Fewer ESCs form
  • Lower rate
32
Q

How does a low concentration of enzyme effect the rate of reaction ?

A

Low rate of reaction as ESCs can’t form

33
Q

How does a high concentration of enzyme effect the rate of reaction ?

A

Rate eventually plateaus as enzymes become saturated if insufficient substrate

34
Q

What are cofactors and coenzymes ?

A

A non protein component of enzymes which allow them to carry out their function

35
Q

How do cofactors and coenzymes work ?

A

Either transfer atoms from one reaction to another or bind to their active site to make them complementary to the substrate

36
Q

Give a feature of a cofactor and how it is obtained

A
  • Inorganic ( doesn’t contain carbon)
  • Obtained via diet as minerals
37
Q

Give an example of a cofactor

A

Amylase which contains chloride ions necessary to form complementary active site

38
Q

Give a feature of a coenzyme and how it is obtained

A
  • Organic
  • Obtained via diet as vitamins
39
Q

Give an example of a coenzyme

A

Coenzyme A from vitamin B5 to break down carbohydrates and fatty acids during respiration

40
Q

What is an enzyme called before cofactor ?

A

Apoenzyme

41
Q

What is an enzyme called after a cofactor is added ?

A

Haloenzyme

42
Q

Give 2 things that can cause a shape change to the tertiary structure of an enzyme

A
  • Change in pH
  • Change in temperature
    ..by proenzmes
43
Q

What is a prosthetic group an example of ?

A

A type of cofactor but is permanently attached to enzyme

44
Q

Give an example of a prosthetic group

A

Haemoglobin with Fe3+ prosthetic group

45
Q

What is the prosthetic group for carbonic anhydrase ?

A

Zn2+

46
Q

Explain precursor activation

A

Enzyme is activated by the binding of a cofactor which causes a change within the tertiary structure so the active site is complementary to the substrate

47
Q

What is a benefit of precursor activation ?

A

Prevents enzymes causing damage within cells

48
Q

Explain non-competitive inhibition

A
  • Inhibitor binds to enzyme at allosteric site which causes a change in shape to the tertiary structure of the enzyme
  • Active site is changed so is no longer complementary to substrate so it can’t bind
  • ESCs can’t form which lowers rate of reaction
49
Q

Give a feature of non-competitive inhibitors

A

Irreversible - tertiary structure has changed so the reaction can’y reach Vmax even by increasing the concentration of enzyme or substrate

50
Q

Give an example of a reversible competitive inhibitor

A

Statins involved in lowering blood cholesterol levels to prevent heart disease

51
Q

Explain competitive inhibition

A
  • Inhibitor is the same shape as substrate so complementary to enzyme active site
    and binds forming an inhibitor-substrate-complex
  • ESCs can’t form which lowers the rate of reaction
51
Q

Give a feature of competitive inhibition

A

Mostly bind reversibly so Vmax can still be reached by increasing concentration of enzyme or substrate

51
Q

Give an example of non reversible competitive inhibitors

A

Aspirin

52
Q

Explain end product inhibition

A
  • Where products of some reactions are reversible inhibitors
  • If a lot of product is present it will inhibit enzymes and slow/stop reaction
53
Q

Give 2 advantages of end product inhibition

A
  • Save resources
  • Enables reaction to be controlled
54
Q

What does Zn 2+ do ?

A

Acts as a prosthetic group for carbonic anhydrase

55
Q

What statistical test should be used to determine the significant difference between two sets of times ?

A

Students t test

56
Q

Give a factor which doesn’t affect the shape of the active site of an enzyme

A

A drop in temperature

57
Q

Give a unit for rate

A

mm2 /s-1

58
Q

How is rate of reaction calculated ?

A

1/time

59
Q

How does a small increase in temperature affect enzyme activity ?

A

Affects bonds involved in the tertiary structure , changes shape of active site which prevents the substrate bonding

60
Q

What is a feature of the effect of a high temperature vs a low temperature

A
  • Effect of high temperature is irreversible
  • Effect of low temperature is reversible
61
Q

With reference to bonding, why is amylase activity low at pH 4 ?

A
  • Ionic bonds are disrupted by high concentration of H+ ions , tertiary structure is affected, shape of active site is altered, substrate can no longer bind to the active site
  • Enzyme is denatured
62
Q

Define biological catalyst

A

A protein that speeds up the rate of reaction in a living organisms without being used up

63
Q

Identify the issue and solution with using a sample of liquidised celery as a source of catalase enzyme

A

Varying catalase concentrations in different celeries so must have a standard volume taken from the same area of the same plant

64
Q

Give a similarity and a difference between the induced-fit enzyme model of enzyme action and lock and key model

A

Similarity: The enzyme remains unchanged after the reaction

Difference: In induced fit, the shape of the enzyme changes so its a better fit for the substrate

65
Q

State how enzymes allow reactions to proceed at a lower temperature

A

They lower the activation energy

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