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AS Biology > Enzymes > Flashcards

Enzymes Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What are enzymes?

A

Biological catalysts that increase the rate of reactions in living organisms

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2
Q

What reaction does catalase catalyse?

A

The breakdown of hydrogen peroxide into water and oxygen

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3
Q

What reaction does amylase catalyse?

A

The breakdown of starch into maltose

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4
Q

What reaction does trypsin catalyse?

A

The breakdown of proteins into peptides and amino acids

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5
Q

Is hydrogen peroxide a substrate, an enzyme or a product?

A

A substrate

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6
Q

Are enzymes globular or fibrous proteins?

A

Globular proteins that have hydrophilic amini acids on their surface and hydrophobic amino acids within their centre

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7
Q

Why are enzymes soluble in water?

A

Because they are globular proteins that have hydrophilic amino acids on their surface

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8
Q

What is the enzyme substrate complex?

A

The binding of a substrate to an active site

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9
Q

The tertiary structure of the active site is c……….. to the structure of the substrate

A

Complementary

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10
Q

Each enzyme is s………… for the substrate it binds to

A

Specific

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11
Q

Why do enzymes increase the rate of reaction?

A

Because they provide an alternate reaction pathway with a lower activation energy.

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12
Q

What is the lock and key theory?

A

The idea that the tertiary structure of the active site is fixed and doesn’t change shape. The substrate molecule therefore slots perfectly into the active site, just like how a key slots into a lock.

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13
Q

What is the induced fit model?

A

The idea that the tertiary structure of the active site actually changes as the substrate molecule binds with the enzyme. As the substrate starts to form bonds with the amino acids in the active site, the tertiary structure of the enzyme adjusts so that the active site moulds itself tightly around the substrate. This change in the tertiary structure of the enzyme ensures that the active site fits perfectly into the substrate.

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14
Q

How can you measure the rate of reaction from a graph?

A

By drawing a tangent

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15
Q

What does the rate of an enzyme controlled reaction depend on?

A

The frequency of successful collisions between the substance and the active site of the enzyme.

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16
Q

How does the temperature affect the rate of enzyme-controled reactions?

A

-Initially, the rate increases because you’re increasing the kinetic energy of both the enzyme and the substrate. Because they’re both moving more rapidly, the chance that the substrate will collide with the active site increases. As a result, more enzyme substrate complexes will be made and so the rate of reaction will increase.

  • At a certain temperature, the optimum temperature has been reached and the reaction is at its optimum. At this point, there’s the maximum frequency of successful collisions between the substrate and the active site.

-As the temperature increases past the optimum temperature, the rate of reaction decreases. The enzymes vibrate more rapidly and these vibrations cause the hydrogen and ionic bonds within the enzyme to break. This causes the tertiary structure of of the enzyme molecules to change . As a consequence, the shape of the active site changes and there comes to a point where it’s no longer complementary to the substrate. Now the substrate can no longer fit into the active site and at this point the enzyme has denatured and can no longer function.

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17
Q

What is Q10?

A

The temperature coefficient

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18
Q

What is the equation for the temperature coefficient?

A

Temperature coefficient= rate of reaction at temperature X at 10 degrees / rate of reaction at temperature X

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19
Q

Why does Q10 usually have a value of around 2?

A

Because generally if the temperature is increased by 10 degrees Celsius, the rate of an enzyme controlled reaction doubles.

(This doesn’t apply above the optimum temperature)

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20
Q

What does the pH of a solution depend on?

A

The concentration of hydrogen ions (H+)

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21
Q

At a low pH is there a low or high concentration of hydrogen ions?

A

There’s a high concentration of hydrogen ions

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22
Q

At a high pH is there a low or high concentration of hydrogen ions?

A

There’s a low concentration of hydrogen ions

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23
Q

How do you workout the pH on a calculator?

A

pH = - log[H+]

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24
Q

What do competitive inhibitors have a similar structure to?

A

The substrate

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25
Q

What happens when a competitive inhibitors binds to the active site?

A

Because it’s not the substrate, no reaction occurs. So after a short time, the competitive inhibitor will leave the active site.

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26
Q

How does a competitive inhibitor reduce the rate of reaction?

A

The competitive inhibitor prevents the actual substrate from colliding with the active site. This reduces the frequency of successful collisions between the substrate and the active site. So less ESC’s are made and the reaction rate is lower.

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27
Q

What is succinate the substrate for?

A

An enzyme involved in respiration

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28
Q

What competitive inhibitor has a similar structure to succinate?

A

Malonate

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29
Q

What does malonate slow down the rate of?

A

Respiration

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30
Q

What is the name of a molecule that competes with substrate molecules for the active site?

A

A competitive inhibitor

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31
Q

How can the effect of a reversible competitive inhibitor on the rate of reaction be reduced?

A

The concentration of the substrate can be increased, whilst the concentration of the competitive inhibitor will be kept the same. Now there’ll be a greater chance of the substrate binding to the active site

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32
Q

Give 2 examples of competitive inhibitors

A

Methotrexate, which is a reversible competitive inhibitor used to treat certain cancers

Penicillin, which is an irreversible competitive inhibitor used to treat bacterial infections

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33
Q

Why can’t the effect of irreversible competitive inhibitors be reversed by increasing the substrate concentration?

A

Because irreversible competitive inhibitors bind permanently to the active site and never leave the active site, no matter the substrate concentration

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34
Q

Do non competitive inhibitors bind to the active site?

A

No

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35
Q

Where do non competitive inhibitors bind?

A

To the allosteric site

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36
Q

What happens to the enzyme when the non competitive inhibitor bonds to the allosteric site?

A

The tertiary structure of the enzyme changes. This results in the shape of the active site changing and so the active site is no longer complementary to the substrate

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37
Q

Why do non competitive inhibitors reduce the rate of reaction?

A

Because they change the shape of the active site and so the substrate can no longer bond to the active site and form an ESC.

38
Q

Why can’t the effect of a non competitive inhibitor be overcome by increasing the substrate concentration?

A

Because the non competitive inhibitor causes the shape of the active site to change and so even with more substrates, none of them will be able to bind successfully to the active site

39
Q

what is important in regulating metabolic pathways in cells?

A

End product inhibition

40
Q

What is a metabolic pathway?

A

A series of reactions, all catalysed by enzymes

41
Q

What 2 things can metabolic pathways do?

A

Break down a molecule e.g. when glucose is broken down to release energy in respiration. To build up larger molecules from smaller ones e.g in the production of certain amino acids

42
Q

What does the final product in the pathway of end product inhibition do?

A

The final product in the pathway inhibits an early-stage enzyme, which reduces the rate of the metabolic pathway

43
Q

What is the end product of respiration?

A

ATP

44
Q

What is end product inhibition an example of?

A

Negative feedback

45
Q

Why is end product inhibition an example of negative feedback?

A

Because it’s used to keep the levels of certain molecules within a set range. If the levels vary, then end product inhibition brings the level back into range.

46
Q

Why is end product inhibition an example of non competitive inhibition?

A

Because end product inhibition takes place through the allosteric site of the enzyme

47
Q

What are the substrates for the amylase enzyme?

A

Starch and water

48
Q

What reaction does amylase catalyse?

A

The hydrolysis of starch to the dissacharide maltose.

49
Q

What needs to happen for the hydrolysis of starch to occur?

A

A chloride ion has to attach to the amylase enzyme. This chloride ion is a cofactor.

50
Q

What is chloride?

A

A mineral ion we get from our diet

51
Q

What are cofactors?

A

Large organic molecules, such as NAD

52
Q

What is a prosthetic group?

A

A permanent part of the enzymes structure , e.g Zn2+

53
Q

What is NAD?

A

A coenzyme, which temporarily binds to many of the enzymes involved in respiration. NAD transfers hydrogen atoms from one molecule to another

54
Q

What are many coenzymes?

A

Vitamins/ mineral ions which are found in our diet

55
Q

What reaction does carbonic anhydrase catalyse?

A

The formation of carbonic acid from carbon dioxide and water. Carbonic anhydrase contains a zinc ion which is permanently bound to the enzyme. This zinc ion is a prosthetic group.

56
Q

What are intracellular enzymes?

A

Enzymes which are produced and functioned inside the cell

57
Q

What are extracellular enzymes?

A

Enzymes which are secreted by cells and so catalyse reactions outside of the cell

58
Q

What are some examples of intracellular enzymes?

A

Catalase, mutase, glycogen synthase, arginase

59
Q

What are some examples of extracellular enzymes?

A

Amylase, trypsin, esterase, sucrase

60
Q

Describe the role of the intracellular enzyme catalase

A

Hydrogen peroxide is produced as a by product of many metabolic reactions and is harmful to cells. Catalase converts hydrogen peroxide into water and oxygen, hence preventing any damage to cells or tissues

61
Q

Describe the role of the extracellular enzyme amylase

A

The hydrolysis of starch (a carbohydrate) into simple sugars

62
Q

Why is digestion usually carried out by extracellular enzymes?

A

Because the macromolecules being digested are too large to enter the cell

63
Q

Describe the role of the extracellular enzyme trypsin

A

Trypsin is secreted by the pancreas and enters the small intestine. It breaks down proteins into peptides and amino acids

64
Q

What is homeostasis?

A

The maintaining of internal body conditions

65
Q

Why do enzymes depend on homeostasis?

A

Because it ensures the perfect conditions for enzymes in the body to function properly

66
Q

Without enzymes….

A

Extremely high temperatures or pressures would be needed to reach the activation energy for many biological reactions

67
Q

What bonds hold the tertiary structure of an enzyme together?

A

Hydrogen and ionic bonds

68
Q

What do changes in pH do to an enzyme?

A

They cause the hydrogen bonds and the ionic bonds in the tertiary structure to break. This alters the shape of the active site and the active site is no longer complementary to the substrate. ESC’s can therefore form less easily or not at all. Hence, the enzyme may become denatured

69
Q

What ph does pepsin work best at?

A

ph 2

70
Q

What pH does urease work best at?

A

ph7

71
Q

What pH does trypsin work best at?

A

pH 8

72
Q

Why should buffer solutions be used when measuring theeffect of pH on the rate of enzyme catalysed reactions?

A

Because buffer solutions help to maintain specific ph’s

73
Q

What happens when starch is in the presence of iodine?

A

There’s a colour change from orange to blue black

74
Q

what happens when maltose in the presence of iodine?

A

There’s no colour change, remains orange

75
Q

What happens to the rate of an enzyme catalysed reaction at low temperatures?

A

The rate decreases. This is because the substrate and the active site have less kinetic energy and so there’s less frequent successful collisions between them. This allows for ESC’s to less likely be formed

76
Q

What happens to the rate of an enzyme catalysed reaction at high temperatures?

A

The enzyme will eventually denature. This is because the enzyme has more kinetic energy and this increased vibration of the enzyme molecules puts a strain on them. This causes the weak hydrogen bonds and ionic bonds that hold the enzyme molecule in its precise shape to start to break. The breaking of these bonds causes the tertiary structure of the enzyme to change. The shape of the active site changes and is no longer complementary to the substrate. ESC’S are less likely to form an the rate of reaction will decrease.

77
Q

What is body temperature?

A

37 degrees Celsius

78
Q

Give an example of thermostable enzymes

A

Some bacteria that live in thermal springs have enzymes that can withstand temperatures above 80 degrees Celsius and so are thermostable

79
Q

What is the definition of the temperature coefficient?

A

The rates of reaction between the rates of that reaction at 2 different temperatures. The rate mostly doubles for every 10 degrees Celsius increase in temperature

80
Q

What bonds do non reversible inhibitors form with enzymes?

A

Covalent bonds

81
Q

What are cofactors?

A

Molecules that help enzymes function properly

82
Q

What are the inorganic ions that enzymes require in order to function properly known as?

A

Inorganic cofactors

83
Q

P…. groups help to form the finl 3D shape of the enzyme

A

Prosthetic

84
Q

During many respiration reactions, which coenzy!es are alternately reduced and oxidised, transferring energy in the form of hydrogen ions?

A

NAD and FAD

85
Q

What does NADP do?

A

the same role as NAD and FAD , but I’m photosynthesis

86
Q

Is ATP a coenzyme?

A

Yes

87
Q

What happens to the rate of reaction when the substrate concentration is low?

A

When the substrate concentration is low, there’s a low frequency of collisions between the substrate and the active site. A lower amount of ESC’s are made and therefore the rate of reaction will be slow.

88
Q

What happens to the rate of reaction when the substrate concentration is high?

A

When the substrate concentration is high, there’s a high frequency of collisions between the substrate and the active site. More ESC’S will be formed and therefore there’ll be a higher rate of reaction

89
Q

Is the rate of an enzyme catalysed reaction directly proportional to the substrate concentration?

A

Yes, so if you double the substrate concentration, the rate of reaction doubles too

90
Q

Is it true that if you keep increasimg the substrate concentration, there comes to a point where the rate stops increasing any further?

A

Yes, and at this point, the enzyme is working at its fastest rate. Scientists call this vmax

91
Q

When is an enzyme said to be saturated?

A

When there’s more substrates than active sites and so there’s no more free active sites for the extra substrate molecules to collide with

92
Q

The rate of enzyme reaction is directly proportional to the enzyme concentration, provided that there’s more substrates than enzyme molecules. However, if the amount of substrate becomes limited, then increasing the enzyme concentration will no longer increase the rate of reaction because there won’t be enough substrate molecules to collide with all of the available active sites. Is this true or false?

A

True

AS Biology (15 decks)

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