Module 2.1.4 - Enzymes Flashcards

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1
Q

What are enzymes?

A

Proteins that speed up the rate of a chemical reaction by acting as a biological catalyst

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2
Q

What do enzymes do?

A
  • Catalyze metabolic reactions at a cellular level and for an organism as a whole
  • can affect structures in an organism (involved in production of collagen)
  • enzyme action can be intracellular or extracellular
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3
Q

What is an intracellular example?

A

Catalyze an enzyme that works inside cells to catalyze the breakdown of hydrogen peroxide to oxygen and water. Hydrogen peroxide is the toxic by-product of several cellular reactions (can kill cells)

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4
Q

What is the structure of enzymes?

A
  • globular protein
  • have an active site which the substrate binds to
  • active site has a specific shape which is determined by the enzymes tertiary structure
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5
Q

What is an extracellular example?

A
  • Amylase works outside cells in the human digestive system. Amylase is found in saliva and it catalyses the breakdown of starch into maltose in the mouth
  • Trypsin catalyses the hydrolysis of peptide bonds (turns big polypeptides into smaller ones). Trypsin is produced by cells in the pancreas and secreted in the small intestine
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6
Q

What is the activation energy?

A

A certain amount of energy needed before a reaction will start

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7
Q

What do enzymes reduce?

A

The amount of energy that is needed to make reactions happen at a lower temperature. This speeds up the rate of reaction

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8
Q

What is formed when a substrate binds to an enzymes active site?

A

An enzymes substrate complex is formed. This lowers the activation energy

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9
Q

What are the reasons for the activation energy lowering?

A
  1. If 2 substrate molecules need to be joined, attaching tot the enzyme holds them close together, reducing any repulsion between the molecules so they can bond more easily
  2. If enzyme is catalysing a breakdown reaction, fitting into the active site puts a strain on bonds in the substrate. The strain means the substrate molecules breaks up more easily
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10
Q

What is the lock and key model?

A

Enzymes only work with substrates that fit their active site with complementary shape. When the enzyme substrate complex is formed, it changes shape slightly, this locks the substrate in more tightly to the enzyme

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11
Q

What is the induced fit model?

A

The substrate doesn’t only have to be the right shape to fit the active site, it has to make the active site change shape in the right way as well

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12
Q

What happens to to the rate of reaction when temp increases?

A

Rate of reaction increases

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13
Q

What factors affect enzyme activity?

A
  • Temperature
  • pH
  • Enzyme concentration
  • Substrate concentration
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14
Q

How does the rate of reaction increase?

A

More heat = more kinetic energy = molecules move faster
This makes the substrate molecules more likely to collide with the active site of an enzyme

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15
Q

What does the energy of the collisions increasing do?

A

Each collision is more likely to result in a reaction

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16
Q

What is the optimum temperature for most reactions

A

37 degrees

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16
Q

What happens if the temperature gets too high?

A

Reaction will stop because the increase in temp causes the enzyme molecule to vibrate. If they vibrate too much it can cause the bonds to hold the enzyme in shape to break/denatured

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16
Q

When does the rate of reaction continue increase until?

A

The enzyme reaches optimum temperature

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17
Q

What does the Q10 value for a reaction show?

A

How much the rate of reaction changes when the temperature is raised by 10 degrees

18
Q

What is the Q10 equation?

A

Q10 = R2 (rate at high temp) / R1 (rate at lower temp)

19
Q

What does the pH of an enzyme do?

A

Is the pH that the enzyme controlled reaction works fastest

20
Q

What happens if the pH goes above or bellow the optimum?

A

The H+ and OH- ions can break the ionic bonds and hydrogen bonds that hold the enzymes tertiary structure in place. This would change the active site of the enzyme and would become denatured

21
Q

What do most human enzymes work best at?

A

pH 7

22
Q

The higher the substrate concentration…?

A

The faster the reaction

22
Q

What happens due to the more enzyme molecules there are in a solution?

A

The more likely a substrate molecule will collide into one of them to form an enzyme substrate complex. This will increase the rate of reaction

23
Q

What happens if the substrate is limited?

A

There is no point adding more enzymes as it will have no further affect

24
Q

What does more substrate molecules mean?

A

More collisions between enzymes and a substrate. This is only true up until saturation point (all the active sites of enzymes are full) and adding more substrate will make no difference

25
Q

What is the limiting factor?

A

Enzyme concentration

26
Q

What do inorganic cofactors do?

A
  • Work by helping the enzyme and substrate bind together
  • don’t directly participate in the reaction so aren’t used up or changed in any way
27
Q

What are the 2 types of cofactors and coenzymes?

A

organic and inorganic

28
Q

What do organic cofactors (coenzymes) do?

A
  • Participate in reactions and are changed by it
  • often act as carriers moving chemical groups between different enzymes
29
Q

What is a prosthetic group?

A

A cofactor is closely bound to the enzyme

30
Q

What are enzyme inhibitors/what do they do?

A

Enzymes can be prevented by enzyme inhibitors (molecules that bind to the enzyme that they inhibit). There are 2 types of inhibitors: competitive and non-competitive

31
Q

What are competitive inhibitors?

A
  • have similar shape to that of a substrate molecule
  • compete with the substrate molecule to bind to the active site but no reaction takes place
  • block the active site
  • if increase conc of inhibitors, will take up most of the active sites and hardly any substrate will get to the enzyme
  • increasing conc of substrate increases the ROR up to a point
32
Q

What are non-competitive inhibitors?

A
  • bind to the enzyme away from the active site called the enzymes allosteric site
  • causes enzyme to change shape so the substrate molecules can no longer bind to it
  • don’t compete with a substrate so increase in conc of substrate will not make any difference (enzyme activity will be inhibited0
33
Q

What are reversible and non-reversible inhibition?

A

Inhibitors can be reversible (not bind permanently to an enzyme) or non-reversible (bind permanently to an enzyme). Which one they are depends on the strength of the bonds between the enzymes and the inhibitors

34
Q

What bonds does non-reversible inhibition have?

A

Strong covalent bonds so inhibitor can’t be removed easily so its non-reversible

35
Q

What bonds does reversible inhibition have?

A

Weak hydrogen bonds/ weak ionic bonds so the inhibitor can be removed so its reversible

36
Q

What can some medical drugs be used as?

A

Inhibitors

37
Q

What do metabolic poisons do?

A

Interfere with metabolic reactions (reactions that occur in cells), causing damage, illness or death

38
Q

Give examples of medical drugs

A

Antiviral drugs
Antibiotics

38
Q

Give examples of metabolic poisons

A

Cyanide
Malonate
Arsenic

39
Q

What is product inhibition?

A
  • metabolic pathways are regulated by end-product inhibition
  • metabolic pathway is a series of connected metabolic reactions
  • product of the 1st reaction takes part in the 2nd and so on…
  • each reaction is catalyzed by a different enzyme
40
Q

What is a metabolic pathway?

A

A series of connected metabolic reactions

41
Q

What is end-product inhibition?

A
  • when final product in metabolic pathway inhibits an enzyme that acts earlier on in the pathway
  • regulated the pathway and controls amount of end-product made
42
Q

Are product and end-product inhibition reversible or non-reversible?

A

Both are reversible

43
Q

What happens when the level of product starts to drop?

A

The level of inhibition will start to fall and the enzyme can start to function again (more product can be made)