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biology > 2.1.4: enzymes > Flashcards

2.1.4: enzymes Flashcards

1
Q

what is an active site?

A

indented are on the surface of an enzyme with a shape that is complementary to the shape of a substrate, meaning only that substrate will fit

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2
Q

what is a catalyst?

A

chemical that speeds up the rate of a reaction by lowering the activation energy by providing an alternative pathway without being used up and reusable

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3
Q

what is meant by extracellular?

A

outside the cell

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4
Q

what is mean by intracellular?

A

inside the cell

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5
Q

what does metabolic/metabolism mean?

A

the chemical reactions that take place inside living cells or organisms

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6
Q

what is a product?

A

a molecule produced from substrate molecule, by an enzyme catalysed reaction

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7
Q

what is a substrate?

A

molecule that is altered by and enzyme-catalysed reaction

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8
Q

why are enzymes called biological catalysts?

A

they speed up metabolic reactions in living organisms

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9
Q

what is meant by the term “turnover number”?

A

number of substrate molecules converted into products per second

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10
Q

what are the advantages of enzymes compared to chemical catalysts?

A

work at lower pressures and temperatures, they are more specific and function well in conditions that sustain life

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11
Q

what are enzymes made from?

A

proteins in the tertiary or quaternary structure

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12
Q

what is shape of the enzyme determined by?

A

the sequence of amino acids in the primary protein structure, which twists and folds in a specific way

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13
Q

how do enzymes and substrates collide?

A

randomly due to molecules having kinetic energy

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14
Q

how does an enzyme catalyse (equation)?

A

enzymes + substrate > enzyme-substrate complex > enzyme-product complex > enzyme + product

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15
Q

what are the steps that an enzyme takes (explain the equation)?

A

substrate enters the active site and the enzyme substrate complex forms. the substrate is the converted into products, which then leave the active site

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16
Q

what energy can be provided to activate a chemical reaction?

A

heat which would increase the kinetic energy, making the more likely to collide

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17
Q

why can’t increasing temperature be used in cells to provide activation energy?

A

will cause proteins to denature and lipid structure in membranes to fall apart

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18
Q

what type of reaction allows 2 substrates to bond?

A

anabolic reaction

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19
Q

what type of reaction occurs when a substrate needs to break down into 2 products?

A

catabolic reaction

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20
Q

what type of enzymes act inside cells?

A

intracellular enzymes

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21
Q

what type of enzymes are secreted out of cells and work elsewhere?

A

extracellular enzymes

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22
Q

what is an example of an intracellular enzyme?

A

catalase that breaks down hydrogen monoxide

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23
Q

what are the products when catalase breaks down hydrogen peroxide?

A

2 water molecules and an oxygen molecule

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24
Q

what is the turnover number for hydrogen peroxide?

A

6 million

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25
Q

what is an example of an extracellular enzyme?

A

digestive enzymes like amylase, pepsin, lipase, trypsin, lactase, maltose, sucrose and peptidases and decomposing enzymes like bacteria and fungi

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26
Q

what does amylase do?

A

starch into maltose

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27
Q

what does pepsin do?

A

proteins into shorter polypeptide chains

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28
Q

what does trypsin do?

A

polypeptides into fatty acids and glycerol

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29
Q

what does lactase do?

A

lactose into glucose and galactose

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30
Q

what does maltase do?

A

maltose into glucose and glucose

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31
Q

what does sucrase do?

A

sucrose into glucose and fructose

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32
Q

what does peptidases do?

A

polypeptides to amino acid

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33
Q

how does fungi work?

A

hyphae secretes enzymes to break down the cell walls/cytoplasm. the substrate breaks down simple soluble molecules. the products are then absorbed into the hyphae and used for growth

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34
Q

what are the 2 models for enzyme action?

A

the lock and key theory and the induced fit model

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35
Q

what is the lock and key theory?

A

the enzyme active site has a fixed rigid shape. a substrate with a complementary shape into the active site

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36
Q

what is the induced fit model?

A

the active site and the substrate shapes don’t fit together at the start but when the substrate comes near the active site triggers a slight change in shape, allowing the substrate to fit

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37
Q

why do cells only need a very small concentration of each different enzyme?

A

they are reused repeatedly

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38
Q

why are enzymes important?

A

important at a cellular level because they catalyse all reactions involved in building up cells, tissues, organs and systems

39
Q

what are 9 factors affecting the rate of enzyme activity?

A

temperature changes, water availability, ph changes, substrate concentration, enzyme concentration, inhibitors, end-products, activators and radiation

40
Q

how does temperature affect enzyme activity?

A

temperature increases = rate of enzyme reaction increases because there is more kinetic energy for successful collisions. at the optimum temperature the enzyme works the best. after the optimum, the rate decreases because the enzymes slowly begin to denature

41
Q

how does temperature denature enzymes?

A

it causes the bonds in the tertiary structure to break, changing the shape of the active site

42
Q

how does ph affect enzyme activity?

A

as ph increases, the rate increases until the optimum ph is reached (when the enzyme works best). when the ph increases further the enzymes will slowly denature and the rate will decrease

43
Q

how does ph denature enzymes?

A

the more hydrogen ions present (low ph), the less the r-groups in the enzyme are able to interact with each other and the bonds will break, causing the active site to change shape

44
Q

how does substrate concentration affect the rate of enzyme activity?

A

as you increase substrate concentration the rate will initially increase because there are more substrates to react but will slowly plateau because the enzyme concentration will become the limiting factor

45
Q

how does enzyme concentration affect the rate of enzyme activity?

A

as you increase the amount of enzymes, the rate will increase because there are more active sites for substrates to go into. the rate will then plateau because the substrate concentration will become the limiting factor

46
Q

what is it called when the rate of enzyme activity plateaus?

A

v max

47
Q

what is an inhibitor?

A

a factor that prevents or reduces the rate of of the enzyme- catalysed reaction

48
Q

what are the 4 types of enzyme inhibitors?

A

competitive or non-competitive and reversible or irreversible

49
Q

what is a competitive inhibitor?

A

have a similar shape to the substrate molecule and they compete with the substrate to join the onto the enzyme active site, blocking the active site

50
Q

what is how much the enzyme is inhibited by a competitive inhibitor depend on?

A

the relative concentrations of the substrate and the inhibitor

51
Q

what are 2 examples of competitive inhibitors?

A

statins and aspirin

52
Q

how do stains work as a competitive inhibitor?

A

bind to the enzyme to make cholesterol (linked to heart disease) meaning less cholesterol is produced

53
Q

how does aspirin work as a competitive inhibitor?

A

binds to the enzyme to make prostaglandins, which make our nervous system more sensitive to pain, meaning we are less sensitive to pain

54
Q

what is meant by a competitive inhibitor which is reversible?

A

they are only temporarily attached to the enzyme

55
Q

what is a non-competitive inhibitor?

A

don’t have a similar shape to the substrate and therefore attach to the to the enzyme but not the active site

56
Q

what is the site called where non-competitive inhibitor binds to?

A

allosteric site

57
Q

how do inhibitors affect the rate of reaction and why?

A

decrease it because they change the shape of the active site

58
Q

what is how much the enzyme is inhibited by a non-competitive inhibitor depend on?

A

nothing. increrasing the concentration of substrates will not make a difference to the rate of reaction

59
Q

are most competitive inhibitors reversible or irreversible?

A

reversible

60
Q

are most non-competitive inhibitors reversible or irreversible?

A

irreversible

61
Q

what are 2 examples non-competitive inhibitors?

A

organophosphates and proton pump inhibitors

62
Q

how does organophosphates work as a non-competitive inhibitor?

A

binds to the enzyme needed for nerve impulse transmission, preventing normal nerve impulses and, leading to paralysis (in insecticides)

63
Q

how do proton pump inhibitors work as non-competitive inhibitors?

A

binds to the enzyme needed to make stomach acid, so less acid is made, preventing stomach ulcers

64
Q

what are 2 other medications (not statins or aspirin) involving enzyme inhibitors?

A

antibiotics and antivirals

65
Q

what do antibiotics do?

A

kill bacteria inside our bodies

66
Q

how do antibiotics work as an inhibitor?

A

inhibit bacterial enzymes (the ones that make new cell walls when they replicate) so they will burst and die, via osmosis

67
Q

how do antiviral work as an inhibitor?

A

bind to viral enzymes to slow down the reproduction of viruses inside our bodies

68
Q

what are inhibitors that can sometimes be used a metabolic poisons?

A

cyanide and arsenic

69
Q

how does cyanide work as a non-competitive inhibitor?

A

binds to enzymes involved in cellular respiration in mammals (cytochrome-c oxidase), meaning respiration can’t occur and the organism dies

70
Q

how does arsenic work as a non-competitive inhibitor?

A

binds to enzymes involved in cellular respiration in mammals (pyruvate dehydrogenase) meaning respiration can’t occur and the organism dies

71
Q

what is the end-product inhibition?

A

when the product of a reaction can inhibit one of the enzymes involved in its own production

72
Q

true or false: end-product inhibitions are irreversible?

A

false. they are reversible

73
Q

why is end-product inhibitions useful?

A

it cuts down on the products that would be a waste

74
Q

what is an example of an end-product inhibition?

A

atp can inhibit the enzyme phosphofructokinase, so once enough atp is made, it inhibits its own production

75
Q

what is an inactive form of an enzyme?

A

pre-cursors

76
Q

what is the role of a pre-cursor?

A

prevent them from causing damage to our cells

77
Q

how can pre-cursors be activated?

A

need to undergo a change in shape of their active site by adding a co-factor

78
Q

what is it called when a pre-cursor is actiavted by a co-enzyme?

A

holoenzyme

79
Q

what other ways, then just adding a co-factor, can pre-cursors be activating?

A

temperature and ph

80
Q

many enzymes need an addition of a non-protein component for them to work. what are these called?

A

co-factors, co-enzymes and prosthetic groups

81
Q

are co-factors organic or inorganic?

A

inorganic molecules or ions

82
Q

how do co-factors work?

A

by helping the enzyme and substrate join

83
Q

do co-factors participate directly in the reaction?

A

no. they are not used up and they are not changed in any way

84
Q

are co-enzymes organic or inorganic?

A

organic molecules

85
Q

do co-enzymes participate in the reaction?

A

yes and they are altered by it

86
Q

how do co-enzymes work?

A

act as carriers, moving chemical groups between different enzymes in metabolic pathways

87
Q

what is an example of a co-factor?

A

chlorine ions needed to activate salivary amylase which digests starch

88
Q

what is an examples of a co-enzyme?

A

many vitamins, like vitamin b3 for respiratory enzymes

89
Q

what are prosthetic groups?

A

co-factors or co-enzymes that are very tightly attached to an enzyme and may even be permanently attached

90
Q

what is an example of a prosthetic group?

A

zinc ions are permanently attached to the enzyme carbonic anhydrase, which is involved in the carbon dioxide in the blood stream

91
Q

what is the method for investigating the effect of substrate concentration on enzyme activity?

A

grind a 2cm piece of potato and 5cm of distilled water to make a smooth paste. place 10cm of hydrogen peroxide in a test tube and use forceps to dip a filter paper disc into the enzyme suspension. drop the filter paper into the hydrogen peroxide and measure the time that is takes from striking to the surface to sink to float up again. then remove the disk and repeat with different concentrations of hydrogen peroxide

92
Q

what is the independent variable in the substrate concentration investigation?

A

concentration of the hydrogen peroxide

93
Q

what is the dependent variable in the substrate concentration investigation?

A

time taken for paper disks to float back up

94
Q

what are the control variables in the substrate concentration investigation?

A

same potato extract, total volume and same temperature

biology (10 decks)

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