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A-level Biology > 4 - Enzymes 🍽 > Flashcards

4 - Enzymes 🍽 Flashcards

1
Q

Enzymes are…

A

biological catalysts

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2
Q

What type of proteins are enzymes?

A

Globular

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3
Q

What causes enzymes to react at faster rates?

A

Interacting with substrate molecules

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4
Q

What is an anabolic reaction?

A

Building up thinhs

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5
Q

What is a catabolic reaction?

A

Breaking down reactions

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6
Q

What do enzymes catalyse in food?

A

Digestion

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7
Q

Define metabolism

A

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

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8
Q

What is the certain point called that enzymes can increase the rate of reactions up to?

A

Vmax (max initial velocity)

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9
Q

The specificity of an enzyme

A

Each enzyme catalyses one biochemical reaction

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10
Q

What is the activation energy?

A

The energy needed to be supplied for most reactions to start

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11
Q

How do enzymes help reduce the activation energy needed?

A

Enzymes help the molecules collide successfully

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12
Q

What is the active site?

A

An area within the 3Y of the enzyme with a shape complementary to the specific substrate

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13
Q

When the substrate is bound to the active site, what is formed?

A

Enzyme-substrate complex

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14
Q

When the substrates react, the products are formed in…

A

An enzyme-product complex

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15
Q

How is the substrate held?

A

In such a way that the right atom-groups are close enough to react

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16
Q

How are temporary bonds formed in an enzyme / substrate?

A

The R-groups within the active site of the enzyme will interact with the substrate

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17
Q

How do temporary bonds help a reaction along?

A

By putting strain on the bonds within the substrate

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18
Q

What is the induced-fit hypothesis?

A

The active site of the enzyme changed shape slightly as the substrate enters

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19
Q

What is the initial intereaction between enzyme/substrate in induced-fit?

A

Weak initial interaction

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20
Q

How do the weak interactions rapidly change in induced-fit?

A

Induces changes in the enzymes 3Y that strengthen the binding, putting strain on the substrate molecule

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21
Q

How does putting strain on the substrate effect the reaction in induced-fit?

A

This weakens a particular bond(s) in the substrate, therefore lowering the activation energy

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22
Q

What does catalase do?

A

Breaks down hydrogen peroxide into water and oxygen quickly, preventing its accumulation

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23
Q

Where is catalase found?

A

In both plant and animal tissues

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24
Q

What is the purpose of most
extracellular enzymes?

A

Released from cells to break down large nutrients into smaller molecules that can enter the cell-surface membrane

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25
Q

What type of organisms need extracellular enzymes?

A

Both single-celled and multi-cellular to make use of polymers for nutrition

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26
Q

Where do single felled organisms release their extracellular enzymes?

A

Directly into their surroundings

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27
Q

How are extracellular organisms used in multicellular organisms?

A

Nutrients are taken in by food, but need to be digested into smaller molecules to be absorbed into the bloodstream

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28
Q

Digestion of starch

What does amylase do?

A

Starch polymers are partially broken down into maltose (disaccharide)

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29
Q

Digestion of Starch

Where is amylase produced?

A

By the salivary glands and the pancreas

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30
Q

Digestion of Starch

Where is amylase released?

A

In saliva in the mouth or in pancreatic juice into the small intestine

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31
Q

Digestion of starch

How is maltose then broken down into glucose (monosaccharide)?

A

By maltase found in the small intestine

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32
Q

Digestion of starch

Why are amylase and maltase needed to turn starch into glucose?

A

It’s small enough to be absorbed by the cells lining the digestive system and then into bloodstream

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33
Q

Digestion of proteins

What is trypsin?

A

A protease

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34
Q

Digestion of proteins

What are proteases?

A

A type of enzymes that catalyses the digestion of proteins into smaller peptides, which can then be broken down further into amino acids

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35
Q

Digestion of proteins

Where is trypsin produced and found?

A

Produced in the pancreas and released with the pancreatic juice into the small intestine

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36
Q

Why is it important reactions don’t happen too fast?

A

Leads to a build up of excess products

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37
Q

What controls the different steps in reaction enzymes?

A

Different enzymes

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38
Q

What regulates the rate and quantity of product formation?

A

Controlling the activity of enzymes at crucial points

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39
Q

What activates enzymes?

A

Cofactors

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40
Q

What inactivates enzymes?

A

Inhibitors

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41
Q

What are inhibitors?

A

Molecules that prevent enzymes from carrying out their normal function of catalysis

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42
Q

What are the two types of inhibitors?

A

Competitive and non-competitive

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43
Q

Competitive inhibition

Step 1 = a molecule or part of a molecule that has a similar…

A

shape to the substrate of an enzyme can fit into that active sit of the enzyme

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44
Q

Competitive Inhibition

Step 2 = this blocks the substrate from entering…

A

the active site, preventing the enzyme from catalysing the reaction

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45
Q

Competitive Inhibition

Step 3 = the enzyme cannot carry out…

A

it’s function and is said to be inhibited

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46
Q

Competitive Inhibition

Step 4 = what is the non-substrate molecule that binds to the active site?

A

A type of inhibitor

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47
Q

Competitive Inhibition

Step 4 = substrate and inhibitor molecules present in a solution will compete…

A

to bind to the active sites of the enzymes catalysing the reaction

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48
Q

Competitive Inhibition

Step 5 = this will reduce the number of…

A

substrate molecules binding to the active sites in a given time and slows down the rate of reaction

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49
Q

Competitive Inhibition

How do most competitive inhibitors bind to the active site?

A

Temporarily so their effect is reversible

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50
Q

Competition Inhibition

What does the degree of inhibition depend on?

A

Relative concentrations of substrate, inhibitor and enzyme

51
Q

Competitive Inhibition

What is an exception to the temporary binding to the active site?

A

Aspirin

52
Q

Competitive Inhibition

What is their effect of rate of reaction?

A

Reduces

53
Q

Competitive Inhibition

What is their effect on the Vmax?

A

Doesn’t change it of the enzyme it inhibits

54
Q

Competitive Inhibition

What inhibitor of an enzyme is used in the synthesis of cholesterol?

A

Statins

55
Q

What can high blood cholesterol levels cause?

A

Heart disease

56
Q

Competitive Inhibition

What active site does aspirin irreversibly inhibit?

A

COX enzymes, preventing the synthesis of prostaglandins and thromboxane = the chemicals responsible for producing pain and fever

57
Q

Non-competitive Inhibition

Step 1 = the inhibitor binds to the enzyme at…

A

a location other than the active site - this location is called the allosteric site

58
Q

Non-competitive Inhibition

Step 2 = the binding of the inhibitor causes…

A

3Y of the enzyme to change, meaning the active site changes shape

59
Q

Non-competitive Inhibition

Step 3 = this results in the active site no longer having a…

A

complementary shape to the substrate so it is unable to bind to the enzyme

60
Q

Non-competitive Inhibition

Step 4 = the enzyme cannot carry out its…

A

function and is said to be inhibited

61
Q

Why is it called non-competitive inhibition?

A

The inhibitor doesn’t compete with the substrate for the active site

62
Q

Non-competitive Inhibition

What does increasing the concentration of inhibitor do to rate?

A

Decrease it as more active sites are unavailable

63
Q

Organophosphates are used as what?

A

Insecticide or herbicides

64
Q

What do organophosphates do?

A

Irreversibly inhibit the enzyme acetyl cholinesterase

65
Q

What does acetyl cholinesterase do?

A

Necessary for nerve impulse transmission

66
Q

What does the absence of acetyl cholinesterase do?

A

Leads to muscle cramps, paralysis and even death if accidentally inhested

67
Q

What is used to treat long term indigestion?

A

Proton pump inhibitors (PPIs)

68
Q

What do PPIs do?

A

Irreversibly block an enzyme system responsible for secreting hydrogen ions into the stomach

69
Q

What are PPIs effective at?

A

Reducing the production of excess acid, which can lead to stomach ulcers

70
Q

Define end-product inhibition

A

The term used for enzyme inhibition that occurs when the product of a reaction acts as an inhibitor to the enzyme that produces it

71
Q

What does end-product inhibition serve as?

A

A negative feedback control mechanism for reactions so excess products are not made and resources aren’t wasted

72
Q

What is end-product inhibition:

Competitive or non-competitive?

A

Non-competitive

73
Q

What is respiration?

A

A metabolic pathway resulting in the production of ATP

74
Q

How is glucose broken down in respiration?

A
  • addition of two phosphate groups to glucose
  • addition of second group results in intial breakdown
75
Q

What enzyme catalyses the addition of a phosphate group to break down glucose?

A

Phosphofructokinase (PFK)

This enzyme is inhibited by ATP

76
Q

What happens when ATP levels are high?

A

More ATP binds to PFK, preventing the addition of the second phosphate to glucose so it isn’t broken down and ATP isn’t produced at the same raye

77
Q

What happens as ATP is used up?

A

Less ATP binds to PFK and the enzyme catalyses the addition of the second phosphate to glucose, resuming respiration and the production of ATP

78
Q

Define a cofactor

A

A non-protein component or metallic ion that is required for an enzymes activity as a catalyst

79
Q

Cofactors can be considered what?

A

“Helper molecules” that assist in biochemical transformations

80
Q

Cofactor = Zn++

Enzyme/protein = ?

A
  • Carbonic anhydrase
  • alcohol dehydrogenase
81
Q

Cofactor = Fe++ or Fe+++

Enzyme/protein = ?

A
  • cytochromes
  • haemoglobin
  • ferredoxin
82
Q

Cofactor = Cu++ or Cu+

Enzyme/protein = ?

A

Cytochrome oxidase

83
Q

Cofactor = K+ or Mg++

Enzyme/protein = ?

A

Pyruvate phosphokinase

84
Q

What is vitamin B3 used to synthesise?

A

NAD and NADP

85
Q

What does NAD do?

A

A coenzyme responsible for transfer of hydrogen atoms between molecules involved in respiration

86
Q

What do NADP do?

A

Similar as NAD but in photosynthesis

87
Q

What does vitamin B5 synthesis?

A

Coenzyme A

88
Q

What does coenzyme A do?

A

Breakdown fatty acids and carbohydrates in respiration

89
Q

What are prosthetic groups?

A

Cofactors as they are required got certain enzymes to carry out their catalytic function

90
Q

How do prosthetic groups add to the structure of proteins?

A

Tightly bound and form a permanent feature

91
Q

What are inactive enzymes called?

A

Inactive precursor enzymes

92
Q

What do inactive precursor enzymes tend to do?

A

Cause damage within cell producing them or to tissues once released

93
Q

How are precursor enzymes activated?

A

Undergo a change in shape (3Y) particularly to the active site

94
Q

What must be added to activate a precursor enzyme?

A

A cofactor

95
Q

Define an apoenzyme

A

An inactive precursor enzyme without its non-protein part (cofactor)

96
Q

Define a holoenzyme

A

The active enzyme with its cofactor added

97
Q

Cofactor =

A

Non-protein part is a metal ion

98
Q

Coenzyme =

A

A small organic molecule

99
Q

What external influences can result in a change in 3Y and activate a precursor enzyme?

A

Changes in conditions such as pH or temperature

100
Q

What type of precursor enzymes are produced when they are activated by external conditions?

A

Zymogens or proenzymes

101
Q

What happens when inactive pepsinogen is released into the stomach to digest proteins?

A

The acid pH brings about the transformation into the active enzyme pepsin

This adaption protects the body tissues against the digestive action of pepsin

102
Q

Factors Affecting Enzyme Activity

Increase in temperature = increased frequency of…

A

…successful collisions between substrate and enzyme = increased rate of reaction

103
Q

Factors Affecting Enzyme Activity

Define the temperature coefficient

A

A measure of how much the rate of a reaction increases with a 10°C temperature increase

104
Q

Factors Affecting Enzyme Activity

What is the symbol for the temperature coefficient?

A

Q10

105
Q

Factors Affecting Enzyme Activity

What is the Q10 for enzyme-controlled reactions?

A

2 as the rate of reaction doubled with a 10°C temp increase

106
Q

Factors Affecting Enzyme Activity

What happens do the bonds holding proteins together at a higher temp?

A

They vibrate more = bonds break = change in precise 3Y = denature

107
Q

Factors Affecting Enzyme Activity

What happens when an enzyme denatures?

A

The enzyme is no longer complementary to the substrate

108
Q

Factors Affecting Enzyme Activity

Define the optimum temperature

A

The temp at which the enzyme has the highest rate of activity

109
Q

Factors Affecting Enzyme Activity

What is the optimum temp in humans?

A

40°C

110
Q

Factors Affecting Enzyme Activity

What is thermophilic enzymes optimum temp?

A

70°C

111
Q

Factors Affecting Enzyme Activity

What is psychrophillic enzymes optimum temp?

A

Below 5°C

112
Q

Factors Affecting Enzyme Activity

What happens to rate with enzymes that have denatured below optimum temp?

A

decrease is rate as they haven’t denatured but are just less active

113
Q

Factors Affecting Enzyme Activity

Enzymes adapted to cold will have what properties?

A
  • more flexible
  • less stable
  • smaller temp changes will denature then
114
Q

Factors Affecting Enzyme Activity

Define the optimum pH

A

The active site will only be at the right shape at a certain hydrogen ions concentration

115
Q

Factors Affecting Enzyme Activity

If the pH changed and denatured enzyme, but then changed back, what will happen?

A

The enzyme will go back to the correct shape = renaturation

116
Q

Factors Affecting Enzyme Activity

What happens if pH is changed significantly?

A

Structure of the enzyme will be irreversibly altered

117
Q

Factors Affecting Enzyme Activity

pH hydrogen ions interact with what, and what causes a change in this interaction?

A

Polar and charged R-groups

  • changing the conc of H+ ions will change the degree of the interactive
118
Q

Factors Affecting Enzyme Activity

A low pH means lots of H+ ions =

A

The less the R-groups are able to interact with each other = bonds break = enzyme changes shape

(Same with high pH)

119
Q

Factors Affecting Enzyme Activity

Which factor is rarely limiting?

A

Substrate and enzyme concentration

120
Q

Factors Affecting Enzyme Activity

What happens when there is an increased number of substrate particles?

A

Higher collision rates with the active site of enzymes = increasing rate

121
Q

Factors Affecting Enzyme Activity

How can you increase the available active sites?

A

Increase the enzyme concentration

122
Q

Factors Affecting Enzyme Activity

What is the Vmax?

A

The rate of reaction is at its maximun

123
Q

Factors Affecting Enzyme Activity

What causes a Vmax?

A

All active sites are occupied by substrate particles and no more enzyme-substrate complexes can be formed until products are released from the active sites

124
Q

Factors Affecting Enzyme Activity

Is the rate of reaction directly proportional to enzyme conc?

A

Yes

A-level Biology (23 decks)

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