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AS BIOLOGY > 4 - Enzymes > Flashcards

4 - Enzymes Flashcards

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1
Q

What ions are added to the pH when it increases? (more alkaline)

A

OH- ions

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2
Q

What ions are added to the pH when it decreases? (more acidic)

A

H+ ions

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3
Q

What happens when enzymes are at their optimum pH?

A

~ The charges in the active site and on the substrate are complementary
~ Greatest number of enzyme substrate complexes form
~ Greatest number of products produced

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4
Q

How does the pH of enzymes affect the time taken for product to form and the volume of product formed?

A

The closer pH to the optimum:
~ The less time taken for product to form
~ The greater the volume of product formed

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5
Q

What is enzyme inactivation caused by?

A

H+ or OH- ions being added to the solution (pH solution becoming more acidic/alkaline)

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6
Q

What structure are enzymes in?

A

Tertiary

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7
Q

What type of proteins are enzymes?

A

Globular proteins

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8
Q

What is the reactive part of an enzyme called?

A

The active site

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9
Q

What are the 4 factors that enzymes are affected by?

A

~ Temperature
~ pH
~ Enzyme/substrate concentration
~ Inhibitors

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10
Q

What is the substrate?

A

The molecule that is changed into the product in the reaction

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11
Q

Why are enzymes specific?

A

Because they only catalyse one type of substrate

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12
Q

What bonds are enzymes held together by?

A

Hydrogen, ionic and disulphide bonds

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13
Q

Why are enzymes important in digestion?

A

Because they hydrolyse polymers into monomers

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14
Q

What are the 2 theories for how enzymes function in a reaction?

A

~ Lock and key theory

~ Induced fit theory

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15
Q

What enzyme was used to come up with the induced fit theory?

A

Lysozyme

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16
Q

Where is the enzyme lysosome found?

A

Tears and saliva

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17
Q

What process is an example of enzymes aiding in hydrolysis?

A

Digestion

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18
Q

What process is an example of enzymes aiding in condensation reactions?

A

DNA polymerase

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19
Q

Where are intercellular enzymes made?

A

Inside the cell

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20
Q

Where are extracellular enzymes made?

A

Outside the cell

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21
Q

How do you convert the time taken for product to form into rate of reaction?

A

1/time

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22
Q

How does low temperature affect enzyme reactions?

A

~ Molecules have lower kinetic energy
~ Fewer enzyme and substrate collisions
~ Fewer enzyme substrate complexes form
~ Fewer products will be produced

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23
Q

How does high temperature affect enzyme reactions?

A

~ Molecules have higher kinetic energy
~ More enzyme and substrate collisions
~ More enzyme substrate complexes form
~ More products will be produced

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24
Q

How does too great temperature affect enzyme reactions?

A

~ Enzymes are denatured as kinetic energy is too great
~ The bonds holding the enzyme in shape are broken so the enzyme and active site shape change
~ Substrate will no longer be complementary to active site
~ Therefore fewer enzyme and substrate collisions
~ Fewer enzyme substrate form
~ Fewer products will be produced

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25
Q

What does it mean in terms of bonds if an enzyme has a greater range of optimum temperature/pH?

A

~ It has more disulphide bonds

~ These bonds are the strongest of the tertiary structure bonds and are most able to withstand variations in temperature

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26
Q

What happens when enzymes are made inactive by a change in pH?

A

~ The charges in the active site and substrate are no longer complementary
~ Therefore it’s harder for enzyme substrates to form as the charges repel so fewer of them form
~ Fewer products are formed

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27
Q

Is enzyme inactivation reversible?

A

Yes - it is caused by only a small change in pH

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28
Q

What can be added to a solution to maintain the optimum pH?

A

A pH buffer

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29
Q

What happens when enzymes are denatured by a large change in pH?

A

~ The bonds holding the enzyme in its structure break
~ So the enzyme and active site shape change and the substrate won’t be complementary
~ Therefore no/less enzyme and substrate collisions
~ No/less enzyme substrate complexes form
~ No/less products will be produced

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30
Q

What is the induced fit theory?

A

~ Substrate collides with active site
~ Active site fits around substrate and is held together by oppositely charged groups
~ Enzyme-substrate complex is formed
~ The change in the enzyme shape puts a strain on the substrate which weakens the bonds so they break more easily - lowering the activation energy
~ The product no longer fits in the active site and is released

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31
Q

What does the final molecule that takes place in a series of reactions do?

A

Acts as a competitive/non-competitive inhibitor to enzyme 1

32
Q

What happens when enzymes are in low substrate concentrations? (1-3vol)

A
  • Fewer enzyme substrate molecules
  • Fewer successful collisions
  • Fewer enzyme-substrate complexes formed
  • Fewer products produced
  • Time taken for reaction to occur is greater
  • Substate conc is limiting factor
33
Q

What happens when enzymes are in high substrate concentrations? (3-9 vol)

A
  • More substrate molecules available to bind
  • More successful collisions
  • More enzyme-substrate complexes formed
  • More products produced
  • Time taken for reaction to occur is less
34
Q

What happens when enzymes are in very high substrate concentrations? (10-20 vol)

A
  • All active sites will be occupied at any one time, so increasing the substrate conc will no longer decrease the time taken for reaction to occur
  • Conc of enzymes is now the limiting factor
  • Most enzyme substrate complexes formed
  • Most products produced
35
Q

What happens when substrates are in low enzyme concentrations? (5-10% stock solution)

A
  • Fewer enzymes available to bind
  • Fewer successful collisions
  • Fewer enzyme-substrate complexes formed
  • Fewer products produced
  • Time taken for reaction to occur is greater
  • Enzyme conc is the limiting factor
36
Q

What happens when substrates are in high enzyme concentrations? (10-30% stock solution)

A
  • More enzymes so more available active sites
  • More successful collisions
  • More enzyme-substrate complexes formed
  • More products produced
  • Time taken for reaction to occur decreases
37
Q

What happens when substrates are in very high enzyme concentrations? (50-100% stock solution)

A
  • More available active sites than substrates so increasing the enzyme conc will no longer decrease the time taken for reaction to occur
  • Substrate conc is the limiting factor
  • Most enzyme-substrate complexes formed
  • Most products produced
  • To decrease the time further an increase in substrate conc is required
38
Q

How do enzyme inhibitors affect the rate of reaction?

A

They decrease the rate of reaction

39
Q

Competitive inhibitors have a ‘what’ shape to the substrate molecule?

A

Similar

40
Q

Competitive inhibitors are ‘what’ to the active site?

A

Complementary

41
Q

What do competitive inhibitors do?

A
  • Bind with an active site on an enzyme forming an enzyme-inhibitor complex
  • They prevent the normal substrate from binding by blocking the active site
  • Less enzyme substrate complexes can form
  • Rate of reaction decreases / time taken increases
42
Q

What do non-competitive inhibitors do?

A
  • Don’t compete with substrate molecules for the active site
  • Bind to the allosteric site and distort tertiary shape of enzyme by breaking bonds
  • Substrate is no longer complementary to active site
  • Enzyme-substrate complexes can’t form
  • Rate of reaction decreases
43
Q

What is an example of a non-competitive inhibitor and what does it do?

A
  • Potassium cyanide
  • Inhibits aerobic respiration
  • Classed as a ‘respiratory inhibitor’
44
Q

What happens if the substrate concentration increases when there are competitive inhibitors present?

A

The level of inhibition decreases as there are more normal substrates that can bind with the active site

45
Q

What happens if the substrate concentration increases when there are non-competitive inhibitors present?

A

It will not increase the rate of reaction because the substrates aren’t complementary to the active site

46
Q

Why do reversible enzymes have less of an affect on the rate of reaction?

A

Because they can come off of the active site so that active site can be used again for a normal substrate

47
Q

What do non-reversible enzyme inhibitors do?

A

Bind permanently to the active site or at the allosteric site

48
Q

What is an example of a competitive inhibitor?

A

Ethylene glycol

49
Q

What is an example of a non-competitive inhibitor?

A

Potassium cyanide

50
Q

Does increasing substrate concentration affect competitive inhibitor effects?

A

Yes because there will be more normal substrates available and the effects of the inhibitors will be decreased

51
Q

Does increasing substrate concentration affect non-competitive inhibitor effects?

A

No it will have no effect because the enzymes will be denatured so won’t be able to bind with the substrates, no matter how many there are

52
Q

How are enzymes produced?

A
  • By culturing microbes in fermentation
  • The microbes produce the enzymes as part of their normal metabolic activity
  • The microbes are then removed and the enzymes are extracted and purified
53
Q

What enzyme does bacillus bacteria produce?

A

Protease

54
Q

What enzyme does the fungus streptomycin produce?

A

Glucose, isomerase

55
Q

What enzyme does the fungus mucor produce?

A

Rennin

56
Q

What enzyme does the fungus aspergillus produce?

A

Pectinase

57
Q

What is the enzyme protease used for?

A
  • Biological washing powder
  • Making meat softer
  • Baby food
58
Q

What is the enzyme glucose/isomerase used for?

A

Fizzy drinks and all sugary food

59
Q

What is the enzyme rennin used for?

A

Vegetarian cheese

60
Q

What is the enzyme pectinase used for?

A

Makes drinks such as fruit drink and wine clear not cloudy

61
Q

Why are enzymes used in large scale industrial production?

A
  • They catalyse biological reactions
  • Speed up rate of reaction
  • Lower activation energies so reactions happen at lower temps and are cheaper
  • There are fewer side reactions so less waste products are formed
62
Q

What are advantages of immobilised enzymes over free enzymes?

A
  • Products aren’t contaminated with the enzyme
  • Enzymes can be reused
  • Enzyme is protected within a physical barrier so it’s more stable at extremes of pH and temperature
  • can be used in continuous processes (product of one reaction can be used as the substrate for another which is catalysed by a different enzyme)
63
Q

What are disadvantages of immobilisation?

A
  • In adsorption the enzyme may become detached and contaminate the product
  • Rate of reaction is slower than with free enzymes
  • The presence of the alginate gel alters the shape of the active site which reduces enzyme activity
  • Chemically bonding the enzyme is complex and expensive
  • Contamination means the whole system must be shut down and vessel re-sterilised
64
Q

What is enzyme immobilisation?

A

Attaching or trapping an enzyme onto/into an inert substance/matrix

65
Q

What is an inert

A

A non-reactive substance

66
Q

What are advantages of using a biosensor?

A
  • Accurate
  • Highly specific
  • Can detect very low concentrations of substrate
  • Quantitative result
67
Q

What is a biosensor used for?

A

In blood glucose testing and environmental analysis

68
Q

Why do enzymes only catalyse one type of substrate?

A

Because enzymes have active sites which are specific and will only be complementary to one type of substrate

69
Q

What is adsorption?

A

When enzymes are held by forces such as covalent/ionic bonds on an adsorbing agent (such as clay particles, glass beads or test strips)

70
Q

What is entrapment?

A
  • When enzymes are mixed with a substance which forms a gel capsule around them
  • The gel forms a matrix in which the enzymes become entrapped
71
Q

What does a transducer do?

A

Converts a chemical change to a small electrical current, which is then read by a meter

72
Q

What is alginate?

A
  • A gel matrix used for entrapment of immobilised enzymes

* Often used to make beads

73
Q

What is a gel membrane?

A

The membrane to which immobilised enzymes can be fixed

74
Q

What are anabolic reactions?

A

Reactions that build up molecules e.g. Protein synthesis

75
Q

What are catabolic reactions?

A

Reactions that break down molecules e.g. Digestion

76
Q

What term is used to refer to all the reactions of the body?

A

Metabolism

77
Q

What are reaction sequences called?

A

Metabolic pathways, which are controlled by enzymes

AS BIOLOGY (13 decks)

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