2.4 enzyme inhibition Flashcards

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1
Q

How does a competitive inhibitor stop enzyme substrate complexes forming?

A

Blocking the active site so substrate molecules can not bind

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2
Q

How is a competitive inhibitor able to block the active site?

A

It has a similar shape to the substrate molecules

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3
Q

What do the competitive inhibitor and substrate molecules have to do?

A

Compete for the active site

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4
Q

What does a competitive inhibitor do?

A

Prevents enzyme substrate complexes forming

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5
Q

What is the degree of inhibition dependant on?

A

The the relative concentrations of substrate and inhibitors

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6
Q

What will happen if there is a high concentration of competitive inhibitors?

A
  • More of the active sites will be taken up (blocked)
  • hardly any substrate will get to the enzyme
  • lower rate of reaction
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7
Q

What will happen if there is a higher concentration of substrate than competitive inhibitor?

A

• increased chance of substrate getting to the active site

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8
Q

Are competitive inhibitors usually reversible or non reversible?

A

Reversible

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9
Q

What does a inhibitor being reversible or irreversible depend on?

A

The strength of the bonds between enzyme and inhibitor

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10
Q

If the inhibition is irreversible what are the bonds like?

A
  • strong covalent bonds

* hard to remove inhibitor

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11
Q

If the inhibition is reversible what are the bonds like?

A
  • weak hydrogen or weak ionic bonds

* weakness means inhibitor can be removed

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12
Q

Where to non competitive inhibitors bind to?

A

The enzymes allosteric site

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13
Q

What do non competitive inhibitors binding to the allosteric site cause?

A

Change in the enzymes tertiary structure

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14
Q

What effect does a change in the enzymes tertiary structure have?

A

Active sites shape is altered

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15
Q

If the active site of an enzyme changes shape what can no longer happen?

A
  • The enzyme and substrate no longer bind

* enzyme can no longer catalase reactions

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16
Q

State what a Non competitive inhibitor does and the effect it has:

A
  • binds to allosteric site
  • changes tertiary structure
  • alters shape of active site
  • substrate can’t bind
  • reactions can’t be catalysed
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17
Q

Do non competitive inhibitors change the active site permanently or temporarily?

A

Permanently

18
Q

What effect does increasing substrate concentration have with a non competitive inhibitor?

A

No effect

19
Q

Are non competitive inhibitors reversible or non reversible?

A

Both

20
Q

Give examples of competitive inhibitors?

A

Stains

Aspirin

21
Q

Are stains reversible or irreversible?

A

Reversible

22
Q

What do stains do?

A

Inhibit the enzyme

23
Q

Give an example of where stains are used:

A

In cholesterol synthesis to reduce blood cholesterol concentration, lowering the risk of heart disease

24
Q

Is aspirin reversible or irreversible?

A

Irreversible

25
Q

What does aspirin do?

A
  • Inhibits the active site of cox enzymes

* prevents the synthesis of chemicals responsible for producing pain and fever

26
Q

Give examples of non competitive inhibitors:

A
  • organophosphates

* proton pump inhibitors

27
Q

What are organophosphates?

A

A spray used as insecticide herbicides

28
Q

What do organophosphates do?

A

Inhibit the enzyme acetyl cholinesterose which is used for nerve impulse transmissions

29
Q

What do proton pump inhibitors do?

A

Block the enzyme responsible for secreting H+ ions into the stomach

30
Q

What are proton pump inhibitors used for?

A

The treatment of long term indigestion

31
Q

What medicinal drugs are enzyme inhibitors?

A
  • some antiviral drugs e.g reverse transcriptase inhibitors

* some antibiotics e.g penicillin

32
Q

What do reverse transcriptase inhibitors do?

A

Inhibit the enzyme reverse transcriptase which catalysed the replication of DNA, this prevents the virus from replicating

33
Q

What does penicillin do?

A
  • Inhibits the enzyme transpeptidase which catalysed the formation of proteins in bacteria cell walls
  • this weakens the cell wall
  • cell bursts bacteria dies
34
Q

The metabolic poison cyanide is a inhibitor how does it work?

A

Inhibits enter cytochrome c oxidase an enzyme catalysing respiration reactions, cells that can’t respire die

35
Q

What does the metabolic poison arsenic do?

A

Inhibits pyruvate dehydrogenase an enzyme catalysing respiration reactions

36
Q

What is a metabolic pathway?

A

Product of 1st reaction involved in second reaction

37
Q

What is product inhibition?

A

When product of one reaction inhibits enzyme of another

38
Q

What is end product inhibition?

A

Where the last product of metabolic pathway inhibits the enzyme in first reaction

39
Q

End product inhibition decreases rate of reaction and therefore product production so what happens?

A

Less inhibition
Causing activated enzymes
More reactions
More products

40
Q

Why is end product inhibition useful?

A

Way of controlling the amount of end product made and controlling metabolic reactions

41
Q

Give an example of end product inhibition

A

Phosphofructokinaise enzyme involved in glucose breakdown to make ATP
ATP inhibits the enzyme limiting ATP production