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Biology IB HL > 8.1 Metabolism > Flashcards

8.1 Metabolism Flashcards

1
Q

What is metabolism?

A

Metabolism describes the sum total of all reactions that occur within an organism in order to maintain life

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2
Q

What do most chemical reactions result in?

A

Most chemical changes in a cell result from a series of reactions (pathways), with each step controlled by a specific enzyme

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3
Q

What is the general role of metabolic pathways?

A

Metabolic pathways allow for a greater level of regulation, as the chemical change is controlled by numerous intermediates

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4
Q

How are metabolic pathways usually organised?

A

metabolic pathways are typically organised into chains or cycles of enzyme-catalysed reactions

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5
Q

What are examples of metabolic pathways in the form of chains?

A

Examples of chains: Glycolysis (in cell respiration), coagulation cascade (in blood clotting)

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6
Q

What are examples of metabolic pathways in the form of cycles?

A

Examples of cycles: Krebs cycle (in cell respiration), Calvin cycle (in photosynthesis)

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7
Q

What is the activation energy?

A

Every chemical reaction requires a certain amount of energy in order to proceed – this is the activation energy (EA)

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8
Q

How do enzymes speed up the rate of reaction?

A

Enzymes speed up the rate of a biochemical reaction by lowering the activation energy

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9
Q

What happens to the substrate when an enzyme binds to it?

A

When an enzyme binds to a substrate it stresses and destabilises the bonds in the substrate

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10
Q

In specific terms, how is the activation energy of an enzyme-substrate reaction lowered?

A

This reduces the overall energy level of the substrate’s transitionary state, meaning less energy is needed to convert it into a product and the reaction proceeds at a faster rate

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11
Q

What does it mean if an enzymatic reaction is exergonic?

A

If the reactants contain more energy than the products, the free energy is released into the system (exergonic)

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12
Q

What are examples of exergonic reactions?

A

These reactions are usually catabolic (breaking down), as energy is released from broken bonds within a molecule

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13
Q

What does it mean if a reaction is endergonic?

A

If the reactants contain less energy than the products, free energy is lost to the system (endergonic)

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14
Q

What are examples of endergonic reactions?

A

These reactions are usually anabolic (building up), as energy is required to synthesise bonds between molecules

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15
Q

What is an enzyme inhibitor? (general definition)

A

An enzyme inhibitor is a molecule that disrupts the normal reaction pathway between an enzyme and a substrate

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16
Q

What types of enzyme inhibitors can there be?

A

Enzyme inhibitors can be either competitive or non-competitive depending on their mechanism of action

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17
Q

What do enzyme inhibitors prevent?

A

Enzyme inhibitors prevent the formation of an enzyme-substrate complex and hence prevent the formation of product

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18
Q

Is enzyme inhibition temporary/permenant?

A

BOTH
Inhibition of enzymes may be either reversible or irreversible depending on the specific effect of the inhibitor being used

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19
Q
  1. What is the first step of a normal enzyme reaction?
A

In a normal reaction, a substrate binds to an enzyme (via the active site) to form an enzyme-substrate complex

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20
Q
  1. What causes an enzyme to bind to a particular substrate?
A

The shape and properties of the substrate and active site are complementary, resulting in enzyme-substrate specificity

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21
Q
  1. How does the active site bind with the substrate? Do any changes need to occur?
A

When binding occurs, the active site undergoes a conformational change to optimally interact with the substrate (induced fit)

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22
Q
  1. What is the role of the conformational change of the active site?
A

This conformational change destabilises chemical bonds within the substrate, lowering the activation energy

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23
Q
  1. What is the result of enzyme-substrate interaction?
A

As a consequence of enzyme interaction, the substrate is converted into product at an accelerated rate

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24
Q

What does competitive inhibition involve?

A

Competitive inhibition involves a molecule, other than the substrate, binding to the enzyme’s active site

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25
Q

What is the competitive inhibitor’s relation to the active site?

A

The molecule (inhibitor) is structurally and chemically similar to the substrate (hence able to bind to the active site)

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26
Q

How does the competitive inhibitor inhibit enzyme activity?

A

The competitive inhibitor blocks the active site and thus prevents substrate binding

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27
Q

How can the effects of a competitive inhibitor be reduced?

A

As the inhibitor is in competition with the substrate, its effects can be reduced by increasing substrate concentration

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28
Q

What does non-competitive inhibition involve?

A

Non-competitive inhibition involves a molecule binding to a site other than the active site (an allosteric site)

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29
Q

What does the binding of a non-competitive inhibitor cause? Where does it bind?

A

The binding of the inhibitor to the allosteric site causes a conformational change to the enzyme’s active site

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30
Q

How does a non-competitive inhibitor inhibit enzymatic activity?

A

As a result of this change, the active site and substrate no longer share specificity, meaning the substrate cannot bind

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31
Q

What can mitigate the effects of a non-competitve inhibitor?

A

NOTHING
As the inhibitor is not in direct competition with the substrate, increasing substrate levels cannot mitigate the inhibitor’s effect

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32
Q

What are the (general) purposes of enzyme inhibition?

A

Enzyme inhibitors can serve a variety of purposes, including in medicine (to treat disease) and agriculture (as pesticides)

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33
Q

What is an example of a use of a competitive inhibitor?

A

An example of a use for a competitive inhibitor is in the treatment of influenza via the neuraminidase inhibitor, RelenzaTM

34
Q

What is an example of a use of a non-competitive inhibitor?

A

An example of a use for a non-competitive inhibitor is in the use of cyanide as a poison (prevents aerobic respiration)

35
Q

What is relenza?

A

Relenza is a synthetic drug designed by Australian scientists to treat individuals infected with the influenza virus

36
Q
  1. What is released from infected cells which is harmful?

relenza

A

Virions are released from infected cells when the viral enzyme neuraminidase cleaves a docking protein (haemagglutinin)

37
Q
  1. How does Relenza prevent infected cells from releasing virions?
A

Relenza competitively binds to the neuraminidase active site and prevents the cleavage of the docking protein

38
Q
  1. What is the final result of reflenza treatment?
A

Consequently, virions are not released from infected cells, preventing the spread of the influenza virus

39
Q

What is cyanide? What does it do?

  1. cyanide
A

Cyanide is a poison which prevents ATP production via aerobic respiration, leading to eventual death

40
Q
  1. What does cyanide bind to?

cyanide

A

It binds to an allosteric site on cytochrome oxidase – a carrier molecule that forms part of the electron transport chain

41
Q
  1. Why is cyanide binding to cytochrome oxidase harmful?
A

By changing the shape of the active site, cytochrome oxidase can no longer pass electrons to the final acceptor (oxygen)

42
Q
  1. What is the final result of cyanide binding?
A

Consequently, the electron transport chain cannot continue to function and ATP is not produced via aerobic respiration

43
Q

What is end-product inhibition?

A

End-product inhibition (or feedback inhibition) is a form of negative feedback by which metabolic pathways can be controlled

44
Q

What is the inhibitor in end-product inhibition?

A

In end-product inhibition, the final product in a series of reactions inhibits an enzyme from an earlier step in the sequence

45
Q

Where the end-product bind to in end-product inhibition?

A

The product binds to an allosteric site and temporarily inactivates the enzyme (via non-competitive inhibition)

46
Q

What is the end result of end-product inhibition?

A

As the enzyme can no longer function, the reaction sequence is halted and the rate of product formation is decreased

47
Q

What is the purpose of end-product inhibition?

A

End-product inhibition functions to ensure levels of an essential product are always tightly regulated

48
Q

What happens if product levels build up?

end-product inhibition

A

If product levels build up, the product inhibits the reaction pathway and hence decreases the rate of further product formation

49
Q

What happens if product levels drop?

end-product inhibition

A

If product levels drop, the reaction pathway will proceed unhindered and the rate of product formation will increase

50
Q

What is isoleucine?

A

Isoleucine is an essential amino acid, meaning it is not synthesised by the body in humans (and hence must be ingested)

51
Q

What are food sources rich in isoleucine?

A

Food sources rich in isoleucine include eggs, seaweed, fish, cheese, chicken and lamb

52
Q

How may isoleucine be synthesised in plants and bacteria?

A

In plants and bacteria, isoleucine may be synthesised from threonine in a five-step reaction pathway

53
Q

What is the first step in isoleucine synthesis?

A

In the first step of this process, threonine is converted into an intermediate compound by an enzyme (threonine deaminase)

54
Q

What can isoleucine bind to?

A

Isoleucine can bind to an allosteric site on this enzyme and function as a non-competitive inhibitor

55
Q

What is isoleucine synthesis an example of?

A

As excess production of isoleucine inhibits further synthesis, it functions as an example of end-product inhibition

56
Q

What is the purpose of end-product inhibition for isoleucine?

A

This feedback inhibition ensures that isoleucine production does not cannibalise available stocks of threonine

57
Q

How can enzyme-catalysed reactions be calculated?

A

The rate of an enzyme-catalysed reaction can be calculated and plotted according to the time taken for the reaction to proceed

58
Q

How can the time taken for an enzyme to catalyse a reaction be measured?

A

The time taken can be measured according to either the amount of product formed or the amount of substrate consumed

59
Q

What is reaction rate the inverse of?

A

reaction rate is the inverse of time taken, meaning that the reaction rate is higher when less time is taken (and vice versa)

60
Q

What formula can be used to calculate the rate of reaction?

A

The rate of reaction can be calculated according to the following formula:

Rate of reaction (s–1) = 1 / time taken (s)

61
Q

What are factors that can influence enzyme reactions/

A

Factors which can influence the rate of an enzyme-catalysed reaction include temperature, pH and substrate concentration

62
Q

What type of substance can be used to affect the kinetics of an enzyme reaction?

A

Competitive and non-competitive inhibitors effect the kinetics of an enzyme-catalysed reaction in different ways:

63
Q

What do competitive and non-competitive inhibitors have in common?

A

Both reduce the rate of reaction by limiting the amount of uninhibited enzyme available for reaction

64
Q

Where do competitive inhibitors bind?

A

Bind directly to the active site and hence exist in direct competition with the substrate

65
Q

How do increased substrate levels affect enzyme activity with competitive inhibitors?

A

Increasing substrate levels will increase the likelihood of the enzyme colliding with the substrate instead of the inhibitor

66
Q

Can the max rate of enzymatic activity be reached with competitive inhibitors?

A

The maximum rate of enzyme activity (Vmax) can still be achieved, although it requires a higher substrate concentration

67
Q

Where do non-competitive inhibitors bind?

A

Bind to an allosteric site and hence do not exist in direct competition with the substrate

68
Q

How do increased substrate levels affect enzyme activity with non-competitive inhibitors?

A

Increasing substrate concentrations will not effect the level of inhibition caused by the non-competitive inhibitor

69
Q

How is the maximum rate of enzymatic activity affected?

A

The maximum rate of enzyme activity (Vmax) is therefore reduced

70
Q

What is malaria?

A

Malaria is a disease caused by parasitic protozoans of the genus Plasmodium

71
Q

What does a life cycle of a parasite involve?

A

The life cycle of the parasite requires both a human and mosquito host – hence the disease is transmitted via mosquito bites

72
Q

What coordinates the growth and maturation of parasites?

A

The maturation and development of the parasite in both human and mosquito host is coordinated by specific enzymes

73
Q

How can anti-malarial drugs be developed?

A

By targeting these enzymes for inhibition, new anti-malarial drugs and medications can be produced

74
Q

What have scientists done to the plasmodium?

A

Scientists have sequenced the genome of infectious species of Plasmodium and used it to determine the parasite’s proteome

75
Q

What can be done with the proteome of plasmodium?

A

From the proteome, enzymes involved in parasitic metabolism have been identified as potential targets for inhibition

76
Q

How can inhibitors be found for the enzymes in plasmodium

A

These enzymes may be screened against a bioinformatic database of chemicals to identify potential enzyme inhibitors

77
Q

What is done to a compound that looks promising as an inhibitor for malaria?

A

Once a promising compound is identified, it may be chemically modified to improve its binding affinity and lower its toxicity

78
Q

What is a way that malaria drugs can be created?

A

An alternative method by which potential new anti-malarial medications can be synthesised is via rational drug design

79
Q

What does rational drug design involve?

A

Rational drug design involves using computer modelling techniques to invent a compound that will function as an inhibitor

80
Q

What does rational drug design produce?

A

Using combinatorial chemistry, a compound is synthesised that is complementary to the active site of the target enzyme

Biology IB HL (56 decks)

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