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Biology Module 2 Foundations In Biology > Chapter 4 Enzymes 2.0 > Flashcards

Chapter 4 Enzymes 2.0 Flashcards

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1
Q

What are enzymes?

A

Biological catalysts that interact with substrate molecules increasing the rate of metabolic reactions.

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2
Q

What are anabolic reactions?

A

Reactions that build smaller molecules into larger molecules- used for growth.

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3
Q

What are catabolic reactions?

A

Reactions that breaks down larger molecules into smaller molecules- used for digestion.

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4
Q

What is metabolism?

A

The sum of all the different reactions and reaction pathways happening in a cell or an organism.

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5
Q

At what point is an enzyme unable to catalyse a reaction?

A

Enzymes can only increase the rates of reaction to the point of V max.

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6
Q

What is V max?

A

Maximum initial velocity or rate of the enzyme-catalysed reaction.

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7
Q

How do enzymes help to catalyse biological reactions?

A

Enzymes reduce the activation energy required for the biological reaction therefore helping more molecules to collide more frequently and effectively.

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8
Q

What type of protein is an enzyme?

A

Globular

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9
Q

Describe the Lock and Key Hypothesis

A

The tertiary structure of the enzyme has a specific active site which is complementary to the shape of the substrate.
During a successful collision between the enzyme and substrate, the substrate will bind to the active site forming an enzyme-substrate complex.
R-groups within the active site of the enzyme will interact with the substrate forming temporary bonds.
The substrate will then react forming the enzyme -product complex. The products will then be released leaving the active site unchanged.

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10
Q

Describe the induced fit model

A

The complementary shape between the active site and the substrate allows them to bind during a successful collision.
The presence of the substrate induces a change to the enzymes tertiary structure, so the active site changes shape slightly to fit the substrate
A enzyme substrate complex is then formed which strengthens binding, putting strain on the substrate molecule lowering activation energy.
Once the products have been made, the enzyme- product complex is formed. The products will be different in shape compared to the substrate allowing the molecules to detach from the active site.

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11
Q

What are intracellular enzymes?

A

Enzymes that act within cells

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12
Q

What type of enzyme is catalase?

A

Intracellular

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13
Q

What is the function of catalase?

A

The enzyme prevents the accumulation of toxic hydrogen peroxide by breaking it down into oxygen and water

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14
Q

What are extracellular enzymes?

A

Enzymes that act outside the cell

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15
Q

What type of enzyme is amylase?

A

Extracellular

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16
Q

What is the function of amylase?

A

Catalyses the hydrolysis of 1-4 glycosidic bonds found in starch.

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17
Q

What type of enzyme is Trypsin?

A

Extracellular

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18
Q

What is the function of Trypsin?

A

Catalyses the break down of proteins into smaller peptide chains.

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19
Q

Why are different enzymes required for biological reactions?

A

Because each enzyme is specific to only one substrate molecule

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20
Q

How is starch digested?

A

Starch polymers are partially broken down into Maltose by the enzyme amylase which is produced by the salivary glands and the pancreas.

Maltose is then broken down into glucose by the enzyme maltase which is present in the small intestine.

Glucose is then small enough to be absorbed into bloodstream.

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21
Q

How are proteins digested?

A

Trypsin is a protease enzyme which breaks down proteins into smaller peptides. Trypsin is produced by the pancreas and released into the small intestine.

Pepsin is a protease enzyme which then catalyses the breakdown of proteins into amino acids. Pepsin is secreted into the stomach.

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22
Q

What factors can affect enzyme activity?

A

Temperature
pH
Substrate and enzyme concentration

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23
Q

How does temperature affect enzyme activity?

A

Increasing the temperature results in more frequent successful collisions between the enzyme and substrate, therefore increasing the rate of reaction.

However, enzyme activity stops once it has exceeded its optimum temperature, this is because the protein becomes denatured.

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24
Q

What is the temperature coefficient?

A

Measure of how the rate of reaction increases with a 10 degrees rise in temperature.

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25
Q

How do enzymes denature as a result of temperature?

A

Increasing temperature above the optimum causes the bonds holding the protein together to vibrate more and eventually break. This results in a change to the precise tertiary structure of the protein and therefore its active site.
This means that the enzyme is no longer complementary to its substrate- it has been denatured.

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26
Q

What is the equation for temperature coefficient (Q10) ?

A

Q10= R2 / R1

R1= represents the rate of reaction at x degrees
R2= represents the rate of reaction at
(x + 10 degrees)

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27
Q

What is optimum temperature?

A

The temperature at which the enzyme has the highest rate of activity.

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28
Q

How does the rate of an enzyme- controlled reaction change once optimum temperature has been exceeded?

A

The rate of reaction decreases rapidly as the active site has been irreversibly changed so the substrate molecules are no longer complementary. This means that biological processes are no longer being catalysed so loss of activity is abrupt.

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29
Q

How does the rate of an enzyme- controlled reaction change when the temperature is below optimum?

A

Below optimum, the decrease in rate of reaction is less rapid as the enzymes have not been denatured but rather are less active.

30
Q

How have enzymes adapted to function in extreme cold temperatures?

A

The enzymes have flexible structures, particularly at the active site. This means they are less stable and less resistant to smaller temperatures changes.

31
Q

How have enzymes adapted to function in extreme hot temperatures?

A

More stable, due to the increased number of hydrogen bonds and disulphide bridges in their tertiary structure.
This means the shape of the active site is more resistant to change as temperature rises.

32
Q

What is the optimum pH?

A

The optimum pH is where the rate of an enzyme- controlled reaction is quickest because the active site has a precise shape which is complementary to a specific substrate at a certain pH.

33
Q

What is the process of renaturation?

A

When the pH changes slightly, the tertiary structure of the enzyme is affected therefore affecting the shape of the active site. However, once the pH returns to its optimum then the enzyme can resume its original shape and catalyse the reaction again.

34
Q

How does pH cause the denaturation of an enzyme?

A

When pH changes significantly, the tertiary structure of the enzyme is irreversibly altered and the active site is no longer complementary to the substrate reducing the rate of reaction. This is because the hydrogen ions interact with the polar and charged R groups.

35
Q

What enzyme(s) act within the saliva and at what pH?

A

Amylase
pH 7-8

36
Q

What enzyme(s) act within the Gastric juice and at what pH?

A

Pepsin acts within the gastric juice of the stomach
pH 1-2

37
Q

What enzyme(s) act within the Pancreatic juice and at what pH?

A

Trypsin, lipase, amylase and maltase acts within the pancreatic juice of the small intestine.
pH 8

38
Q

What effect does changing substrate concentration have on the rate of an enzyme- controlled reaction?

A

Increasing the concentration of a substrate means there are more substrate molecules in a given volume.
This increase the rate of reaction as more frequent successful collisions can take place between the enzyme and substrate molecules.
Therefore, a higher number of enzyme-substrate complexes are formed, producing more products per second.

39
Q

What effect does changing enzyme concentration have on the rate of an enzyme- controlled reaction?

A

When enzyme concentration increases, this means there is a greater availability of active sites in a given volume. This means more enzyme- substrate complexes are formed and more products are produced per second, increasing the rate of reaction.

40
Q

What is a limiting factor?

A

A factor, when in short supply, will prevent the enzyme-controlled reaction from occuring at its maximum rate.

41
Q

What is the limiting factor when changing substrate concentration reaches its maximum rate?

A

The rate of reaction is at its maximum as all the active sites have become saturated, therefore the number of available active sites/ enzyme concentration has become the limiting factor.

No more enzyme- substrate complexes can form unless enzyme concentration is increased.

42
Q

What is the limiting factors when changing enzyme concentration reaches its maximum rate?

A

The rate of reaction is at its maximum, as the active sites of all the enzymes have been saturated by the substrate molecules. Therefore, the substrate concentration has become the limiting factor.

43
Q

What are inhibitors?

A

Molecules that prevent enzymes from catalysing certain reactions or slow them down.

44
Q

What are the two types of inhibitors?

A

Competitive
Non-competitive

45
Q

Describe the process of competitive inhibition

A

-A molecule which has a similar shape to the substrate of an enzyme can fit into the active site of the enzyme
-This then blocks the substrate from the active site, preventing the enzyme from catalysing the reaction
-Therefore, this reduces the number of substrate molecules binding to the active sites in a given time, slowing the rate of reaction.

46
Q

What is the effect of competitive inhibitors to the enzyme?

A

Most competitive inhibitors bind temporarily to the active site, so their effect is reversible.

47
Q

What is the effect of competitive inhibition on rate of reaction?

A

Competitive inhibitors reduce the rate of reaction for a given concentration of substrate, however it does not change the V max of the enzyme.

48
Q

How can the effect of competitive inhibition on the rate of reaction be reduced?

A

If substrate concentration is increased

49
Q

Give examples of competitive inhibitors

A

-Statins
-Aspirin

50
Q

How do Statins work as competitive inhibitors?

A

Statins are competitive inhibitors of an enzyme used in the synthesis of cholesterol.

51
Q

How does Aspirin work as a competitive inhibitor?

A

Aspirin irreversibly inhibits the active site of COX enzymes, preventing the synthesis of chemicals responsible for producing pain and fever.

52
Q

Describe the process of Non competitive inhibition

A

-The inhibitor binds to the enzyme at the allosteric site
-The binding causes the tertiary structure of the enzyme to change, meaning the active site changes shape
-Therefore, the active site is no longer complementary to the substrate molecule so the enzyme cannot catalyse the reaction

53
Q

What is the effect of Non competitive inhibition on the rate of reaction?

A

The V max is not reached, even when the concentration of enzyme or substrate molecules is increased as it will not overcome the effect of the non-competitive inhibitor.
However, by increasing the concentration of the inhibitor the rate decreases further as more active sites become unavailable.

54
Q

What are irreversible inhibitors?

A

Irreversible inhibitors form strong covalent bonds with their enzymes which cannot be easily overcome.

55
Q

What are reversible inhibitors?

A

Reversible inhibitors form weak hydrogen or ionic bonds with the enzymes which can easily be overcome.

56
Q

Give examples of non-competitive inhibitors

A

-Proton pump inhibitors
-Organophosphate

57
Q

How do Organophosphates work as non-competitive inhibitors?

A

Organophosphates are used in insecticides and herbicides which irreversibly inhibit the enzyme necessary for nerve impulse transmission.

58
Q

How do Proton pump inhibitors work as non-competitive inhibitors?

A

Proton pump inhibitors treat long term indigestion by irreversibly blocking the enzyme system responsible for secreting Hydrogen ions into the stomach.

59
Q

What is End product inhibition?

A

When the final product in a metabolic pathway inhibits an enzyme that acts earlier on in the pathway.
Therefore, this controls the amount of of product which is made, so resources are not wasted.

60
Q

What type of inhibition is end product inhibition?

A

Non-competitive reversible inhibition

61
Q

Give an example of end product inhibition

A

Phosphofructokinase is an enzyme involved in the metabolic pathway that breaks down glucose to make ATP.
ATP inhibits the action of the PFK enzyme, so a high level of ATP prevents more ATP from being made.

62
Q

What are cofactors?

A

Non- protein inorganic molecules that help the enzyme and substrate to bind together.
Cofactors don’t directly participate in the reaction so aren’t used up or changed in any way.

63
Q

What is the cofactors of amylase?

A

Cl^-

64
Q

What are Coenzymes?

A

A form of cofactor,non- protein organic molecules that participate in the reaction and are changed by it.
They often act as carriers, moving chemical groups between different enzymes, and are continually recycled during this process.

65
Q

What are sources of coenzymes?

A

Vitamins

66
Q

What are Prosthetic groups?

A

A form of cofactor that is tightly bound to the enzyme.

67
Q

What is the prosthetic group for carbonic anhydrase?

A

Zn^2+

68
Q

What are precursor enzymes?

A

Enzymes that are produced in an inactive form, particularly enzymes that can cause damage within the cells producing them, to tissues where they are released or enzymes that require activation under certain conditions.

69
Q

How do Precursor enzymes become activated?

A

The enzymes often need to undergo a change to their tertiary structure to become activated. This can be done through the addition of a cofactor, the action of another enzyme or a change in conditions.

70
Q

What is denaturation?

A

This is where external factors, such as an increase in temperature or change in pH, can disrupt the tertiary structure bond and irreversibly change the shape of the active site.

71
Q

Why are enzymes degraded?

A

Some enzymes may be abnormally shaped, this prevents them from accumulating and harming the cell.
Enzyme in excess or not essential are also degraded.

72
Q

Some enzymes work better in the presence of other molecules or ions.
Explain how these molecules or ions increase the activity of enzymes.

A

The attached prosthetic groups, co-enzymes, cofactors bind to the enzyme which induce the active site to change its shape as the tertiary structure has been altered.
This means there are more successful collisions and so more enzyme-substrate complexes are formed meaning the rate of reaction is greater.

Biology Module 2 Foundations In Biology (7 decks)

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