1.4 (biological molecules) Flashcards

enzymes

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1
Q

enzymes are biological

A

catalysts

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2
Q

enzymes are catalysts because they

A

speed up the rate of chemical reactions without being used up or changed

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3
Q

critical to the enzymes function is the active site where the what binds

A

substrate

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4
Q

metabolic pathways are controlled by

A

enzymes in a biochemical cascade of reactions

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5
Q

enzymes can be what referring to whether they are active inside or outside the cell

A
  • intracellular
  • extracellular
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6
Q

intracellular enzymes are

A
  • produced and function
  • inside the cell
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7
Q

extracellular enzymes are

A
  • secreted by cells
  • catalyse reactions outside cells (eg. digestive enzymes in the gut)
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8
Q

hydrogen peroxide is produced as a by- product of many metabolic reactions, it is harmful to cells, catalase does what

A
  • converts hydrogen peroxide into water and oxygen
  • preventing any damage to cells or tissues
  • intracellular
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9
Q

digestion is usually carried out by extracellular enzymes, this is because

A
  • macromolecules being digested
  • too large to enter the cell
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10
Q

amylase is involved in carbohydrate digestion it

A

hydrolyses starch into simple sugars

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11
Q

amylase is secreted by

A
  • the salivary glands and the pancreas
  • for digestion of starch in the mouth and small intestine
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12
Q

enzymes have an active site where specific substrates bind forming an

A

enzyme-substrate complex

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13
Q

the active site of an enzyme has a specific shape to fit a

A

specific substrate

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14
Q

extremes of heat or pH can change the shape of the

A
  • active site
  • preventing substrate binding
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15
Q

extremes of heat or pH can change the shape of the active site, preventing substrate binding, this is called

A

denaturation

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16
Q

the specificity of an enzyme is a result of the

A
  • complementary nature
  • between the shape of the active site on the enzyme and its substrates
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17
Q

the shape of the active site (and therefore the specificity of the enzyme) is determined by the complex what structure of the protein that makes up the enzyme

A

tertiary

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18
Q

proteins are formed from

A

chains of amino acids held together by peptide bonds

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19
Q

the order of amino acids determines the what of an enzyme

A

shape

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20
Q

the enzyme-substrate complex is only formed

A

temporarily

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21
Q

the enzyme-substrate complex is only formed temporarily, before the enzyme

A

catalyses the reaction and the product(s) are released

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22
Q

enzyme reactions can either be

A

catabolic or anabolic

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23
Q

catabolic reactions involve the

A

breakdown of complex molecules into simpler products

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24
Q

catabolic reactions involve the breakdown of complex molecules into simpler products, which happens when

A

a single substrate is drawn into the active site and broken apart into two or more distinct molecules

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25
Q

catabolic reaction diagram

A
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26
Q

examples of catabolic reactions include

A
  • cellular respiration
  • hydrolysis reactions
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27
Q

anabolic reactions involve the

A

building of more complex molecules from simpler ones

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28
Q

anabolic reactions involve the building of more complex molecules from simpler ones by

A
  • drawing two or more substrates into the active site
  • forming bonds between them
  • and releasing a single product
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29
Q

anabolic reaction diagram

A
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30
Q

examples of anabolic reactions include

A

protein synthesis and photosynthesis

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31
Q

enzymes work by lowering the

A

activation energy of a reaction

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32
Q

for a reaction to proceed there must be enough

A

activation energy

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33
Q

activation energy is the

A
  • amount of energy needed by the substrate to become just unstable enough for a reaction to occur - and for products to be formed
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34
Q

enzymes speed up chemical reactions because they influence

A

the stability of bonds in the reactants

35
Q

the destabilisation of bonds in the substrate makes it more

A

reactive

36
Q

enzymes work by lowering the activation energy of a reaction and in doing so they provide

A

an alternative energy pathway

37
Q

exothermic activation energy diagram

A
38
Q

enzymes are globular proteins, this means their shape (as well as the shape of the active site of an enzyme) is determined by the complex

A

tertiary structure of the protein that makes up the enzyme and is therefore highly specific

39
Q

in the induced fit hypothesis the enzyme and its active site (and sometimes the substrate) can

A

change shape slightly as the substrate molecule enters the enzyme

40
Q

the enzyme and its active site can change shape slightly as the substrate molecule enters the enzyme, these changes in shape are known as

A

conformational changes

41
Q

conformational changes ensures an

A

ideal binding arrangement between the enzyme and substrate is achieved

42
Q

conformational changes maximises

A

the ability of the enzyme to catalyse the reaction

43
Q

what are the four actors affecting enzymes

A
  • temperature
  • pH
  • enzyme concentration
  • substrate concentration
44
Q

enzymes have a specific optimum temperature, the temperature at which

A

they catalyse a reaction at the maximum rate

45
Q

lower temperatures either prevent reactions from proceeding or slow them down as molecules move

A

relatively slow

46
Q

molecules moving slow in a reaction means

A
  • lower frequency of successful collisions between substrate molecules and active site of enzyme
  • less frequent enzyme-substrate complex formation
47
Q

lower temperatures in reactions mean that substrate and enzyme collide with less

A
  • energy
  • making it less likely for bonds to be formed or broken (stopping the reaction from occurring)
48
Q

higher temperatures speed up reactions as molecules move

A

more quickly

49
Q

molecules moving fast in a reaction means

A
  • higher frequency successful collisions between substrate molecules and active site of enzyme
  • more frequent enzyme-substrate complex formation
50
Q

higher temperatures in reactions mean that substrate and enzyme collide with more

A
  • energy
  • making it more likely for bonds to be formed or broken (allowing the reaction to occur)
51
Q

however, as temperatures continue to increase, the rate at which an enzyme catalyses a reaction drops sharply, as the enzyme begins to

A

denature

52
Q

during denaturation the bonds

A

(eg. hydrogen bonds) holding the enzyme molecule in its precise shape start to break

53
Q

breaking of bonds during denaturation causes the

A

tertiary structure of the protein (ie. the enzyme) to change

54
Q

the tertiary structure of the protein changing permanently damages the

A
  • active site, preventing the substrate from binding
  • denaturation has occurred if the substrate can no longer bind
55
Q

high temperatures causes the hydrogen bonds between amino acids to break, changing the

A

conformation of the enzyme

56
Q

hydrogen and ionic bonds hold the

A

tertiary structure of the protein together

57
Q

below and above the optimum pH of an enzyme, solutions with an excess of H+ ions (acidic solutions) and OH- ions (alkaline solutions) can cause these bonds to

A

break

58
Q

pH can cause these bonds to break which alters the shape of the

A
  • active site
  • which means enzyme-substrate complexes form less easily
59
Q

when investigating the effect of pH on the rate of an enzyme-catalysed reaction, you can use buffer solutions to measure the rate of reaction at different pH values

A
  • buffer solutions each have a specific pH
  • buffer solutions maintain this specific pH, even if the reaction taking place would otherwise cause the pH of the reaction mixture to change
  • a measured volume of the buffer solution is added to the reaction mixture
  • this same volume (of each buffer solution being used) should be added for each pH value that is being investigated
60
Q

the higher the enzyme concentration in a reaction mixture, the greater the number of

A
  • active sites available - and the greater the likelihood of enzyme-substrate complex formation
61
Q

if the amount of substrate is limited, at a certain point any further increase in enzyme concentration will not increase the reaction rate as the amount of substrate becomes a

A

limiting factor

62
Q

the effect of enzyme concentration on the rate of an enzyme-catalysed reaction graph

A
63
Q

the greater the substrate concentration, the higher the

A

rate of reaction

64
Q

as the number of substrate molecules increases, the likelihood of

A

enzyme-substrate complex formation increases

65
Q

if the enzyme concentration remains fixed but the amount of substrate is increased past a certain point, however, all available active sites eventually become

A
  • saturated
  • any further increase in substrate concentration will not increase the reaction rate
66
Q

when the active sites of the enzymes are all full, any substrate molecules that are added have nowhere to

A

bind in order to form an enzyme-substrate complex

67
Q

the effect of substrate concentration on the rate of an enzyme-catalysed reaction graph

A
68
Q

an enzymes activity can be reduced or stopped temporarily by a

A

reversible inhibitor

69
Q

two types of reversible inhibitors are

A
  • competitive
  • non competitive
70
Q

competitive inhibitors have a similar shape to that of the

A
  • substrate molecules
  • therefore compete with the substrate for the active site
71
Q

non-competitive inhibitors bind to the enzyme at an

A
  • alternative site
  • which alters the shape of the active site
  • therefore prevents the substrate from binding to it
72
Q

competitve inhibition diagram

A
73
Q

non competitve inhibition diagram

A
74
Q

reversible inhibitors can act as regulators in

A

metabolic pathways

75
Q

metabolic reactions must be very

A
  • tightly controlled
  • and balanced
  • so that no single enzyme can ‘run wild’ and continuously and uncontrollably generate more and more of a particular product
76
Q

metabolic reactions can be controlled by using the

A

the end-product of a particular sequence of metabolic reactions as a non-competitive, reversible inhibitor

77
Q

as the enzyme converts substrate to product, the process is itself slowed down as the

A
  • end-product of the reaction chain binds to an alternative site on the original enzyme
  • changing the shape of the active site
  • and preventing the formation of further enzyme-substrate complexes
78
Q

the end-product can then detach from the enzyme and be used elsewhere, allowing

A

the active site to reform and the enzyme to return to an active state

79
Q

this means that as product levels fall, the enzyme begins

A

catalysing the reaction once again, in a continuous feedback loop

80
Q

end product inhibition diagram

A
81
Q

for competitive inhibitors, countering the increase in inhibitor concentration by increasing the substrate concentration can

A

increase the rate of reaction once more (more substrate molecules mean they are more likely to collide with enzymes and form enzyme-substrate complexes

82
Q

for non-competitive inhibitors, increasing the substrate concentration cannot

A

increase the rate of reaction once more, as the shape of the active site of the enzyme remains changed and enzyme-substrate complexes are still unable to form

83
Q

the effect of inhibitor concentration on the rate of an enzyme-catalysed reaction graph

A