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A Level Biology > Chapter 4 - Enzymes > Flashcards

Chapter 4 - Enzymes Flashcards

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1
Q

metabolism definition?

A

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

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2
Q

in which 2 ways can reactions be sped up?

A

increasing temp - but can damage cells, denature proteins

2- catalyst

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3
Q

what is a catalyst?

A

a chemical that speeds up the rate of reaction and remains unchanged and reusable at the end of the reaction

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4
Q

what is a substrate?

A

any molecule that can have a reaction catalysed by an enzyme

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5
Q

what is an enzyme’s turnover rate?

A

the number of substrates an enzyme can catalyse in one minute

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6
Q

what is an active site?

A

the reactive part of an enzyme

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7
Q

what is complementary binding?

A

refers to when 2 molecules fit together to complete each other

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8
Q

what is activation energy?

A

the energy required to start a reaction

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9
Q

why will a reaction with a lower activation energy occur faster?

A

bc there will be more molecules with sufficient energy to react

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10
Q

enzymes catalyse reactions by lowering the ______ _____

A

activation energy required for the reaction to occur

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11
Q

how is the activation energy lowered?

A

when a substrate(s) binds to the active site, it is held in a specific orientation that facilitates its reaction
- bc it is held in such an efficient way that it makes all the chemical groups want to react

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12
Q

The active site can also ______ put pressure on the substrate, further lowering the ________ _____

A

physically, activation energy

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13
Q

enzyme mechanism- how do they work ?

A
  • biological reactions take part in solution where enzymes and substrates are free to move around (cytoplasm)
  • when a substrate collides with the correct enzyme, it binds with its active site forming an enzyme substrate complex
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14
Q

assumption of the lock and key model?

A

the enzymes active site is rigid and permanently complementary to the shape of its substrate, substrate fits perfectly into active site
- if substrate is wrong shape, no reaction will occur

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15
Q

what is the flaw of the lock and key hypothesis?

A

scientists discovered that the active sites are flexible in their shapes

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16
Q

induced fit model explanation?

A
  • the enzyme’s active site is usually relaxed and not exactly complementary to the shape of the substrate, so they do not fit exactly together
  • substrate INDUCES a conformational change in the shape of the enzyme
  • the enzyme twists the substrate, making the bonds easier to break or pushes substrates closer together encouraging a link to be formed, AE is lowered
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17
Q

INDUCEd fit

A

substrate binding INDUCES active site to change shape

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18
Q

2 types of metabolic reactions that occur in the body are ?

A

(enzymes catalyse both)

- anabolic, catabolic

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19
Q

anabolic reactions definition

A

metabolic reactions that build molecules

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20
Q

catabolic reactions definition?

A

metabolic reactions that break down molecules

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21
Q

enzymes often work together to form more complex products, by …

A

using the products of one reaction as the substrate for a second

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22
Q

a series of enzymes can work together to form a ….

A

metabolic pathways e.g. Calvin Cycle

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23
Q

intracellular enzymes?

A

enzymes that work within cells

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24
Q

intracellular enzymes work within 2 types of intracellular enzymes:

A
  • some are free moving within a cytoplasm

- some are fixed in place by binding with a membrane (mitochondria)

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25
Q

enzymes can affect both the _____ and ____ of bio moelcules

A

structure, function

e.g. can turn ADP -> ADP

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26
Q

Catalase?

A
  • breaks down poisonous hydrogen peroxide into harmless carbon dioxide and water
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27
Q

extracellular enzymes?

A

enzymes that work outside of cells

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28
Q

digestion definition?

A

the breakdown of large insoluble molecules into smaller soluble molecules

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29
Q

what does protease do

A

breaks down proteins -> amino acids

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30
Q

what does lipase do?

A

lipids -> fatty acids, glycerol

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31
Q

what does carbohydrase do?

A

carbohydrates -> individual sugars like glucose

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32
Q

some extracellular enzymes can be excreted outside of the body?

A

to the external envir

- e.g. tears contain enzymes, mushrooms

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33
Q

amylase ?

A
  • extra
  • digestive enzyme secreted from salivary gland & pancreas
  • breaks down starch -> maltose
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34
Q

Trypsin?

A

extra

  • a protease that acts in the lumen of the small intestine
  • HYDROLYSES PEPTIDE BONDS - breaks down proteins -> amino acids
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35
Q

what is the point of cofactors?

A

some enzymes can only work if they have a certain non-protein molecule attached to them

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36
Q

what is a cofactor?

A

substances that must be present to enable enzymes to catalyse reaction at the appropriate rate

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37
Q

cofactors work in 2 main ways:

A
  • cofactors can affect the charges on either the substrate or the enzyme’s active site
  • cofactors can pair with a substrate to form the correct shape to fit in an active site - these are called co- substrates
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38
Q

Contractors can bind to prosthetic groups permanently and are called ?

A

Prosthetic groups

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39
Q

Prosthetic groups definition?

A

Are inorganic cofactors that are permanently bound to an enzyme and form part of it’s structure

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40
Q

Organic non protein molecules are called?

A

Coenzymes

41
Q

Coenzymes definition?

A

Are organic molecules that temporarily bind to the active site of enzyme either right before or at the same time as the enzyme-substrate complex forms

42
Q

UNLIKE enzymes, coenzymes are

A

CHANGED by the reaction they help catalayse

43
Q

Energy profile diagram - between substrates and products is

A

TRANSITION STATE

44
Q

The rate of reaction is

A

The speed at which a reaction occurs

45
Q

What affects ROR?

A
  • Conc of enzymes and substrates

- temp, PH

46
Q

What are optimal conditions?

A

Conditions that maximise an enzymes ROR

47
Q

As substrates are used up, enzymes

A

Take LONGER TO COLLIDE with the next one

48
Q

The effect of temp on rate?

A

When temp ⬆️ of a solution, KE of enzyme & sub molecules increases, so chance of sucessful collisions increases, rate of ESC formation increases

  • optimum - IROR is highest as max KE, max chance of SC & enzyme hasn’t started to denatrue yet
  • denatured - more and more denature (NOT ALL AT ONCE OTHERWISE WOULD BE STRAIGHT LINE DOWN)
49
Q

What is the temperature coefficient?

A

The temp coefficient for a specific reaction is the effect of a 10°C rise in temp on the rate of reactiob

50
Q

The effect of PH on rate?

A
  • Acids and alkalis can affect the shape of proteins
  • the H plus and OH minus ions can change the way chemical groups react with each other so can affect shape of protein, denatures
51
Q

Enzymes can be activated by _____ and deactivated by ______

A

Cofactors - activation

Inhibitiors- deactivation

52
Q

Inhibitors definition?

A

molecules that prevent enzymes from carrying out their normal function of catalysis (or slow them down)

53
Q

Competitive inhibitors?

A
  • fits into the active site of an enzyme instead of a substrate- so it competes with the substrate
  • these inhibitors form a physical barrier that prevent the formation of an enzyme substrate complexes
54
Q

Non competitive inhibitors?

A
  • bind to a separate part of an enzyme called its allosteric site
  • binding to a non-competitive inhibitor causes a conformational change in the enzyme.
  • this alters the shape of the enzyme’s active site so that it is not complementary with its substrate, substrate cannot bind, ESCs can’t form
55
Q

End product inhibition?

A
  • enzymes can work together to complete metabollic processes
  • most of the time, a cell will only want a certain amount if a mol being produced.
  • in some cases, one of the products acts as an inhibitor to another enzyme in the pathway
56
Q

If the inhibitor is non competitive and the last product ij the pathway it is called?

A

End product inhibition

57
Q

How is end product inhibition an example of negative feedback loop?

A
  • If conc of final product is high the more inhibition can occur
  • greater inhibition will lead to a decrease in the amount of end product being produced
  • if conc of end product decreases, inhibition does too
58
Q

what type of protein are enzymes?

A

gloubular

59
Q

what is the V max ?

A

max IROR or rate of the enzyme catalysed reactions

60
Q

Enzymes lower the ?

A

activation energy

61
Q

when enzyme denatures?

A

the active site changes first and is no longer complementary to the substrate

62
Q

what is end product inhibition?

A

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

63
Q

the difference between cofactors and coenzymes?

A

if the cofactor is an organic molecule it is called a coenzyme

64
Q

prosthetic groups are a ______ feature of the protein

A

permenant

65
Q

precursor enzymes?

A
  • many enzymes are produces in an inactive form, known as inactive precursor enzymes, particularly damaging enzymes or enzymes whose action needs to be controlled
66
Q

what are enzymes ?

A
  • globular proteins that are biological catalysts
67
Q

ANABOLIC + CATABOLIC REACTIONS =

A

METABOLIC REACTIONS

68
Q

what can we measure to calc the enzyme’s ROR?

A
  • the build up of products
  • reduction of reactants
  • change in colour
  • change in PH
69
Q

the gradient at 0 sec gives IROR which is max ROR in these condition:

A
  • enzyme conc
  • sub conc
  • temp
  • PH
70
Q

factors affecting rate of enzyme catalysed reactions - enzyme conc?

A
  • as E conc increases, ROR increases

- when E conc is 2x, no.of active sites is 2x so chance of successful collisions is also 2x

71
Q

factors affecting rate of enzyme catalysed reactions - sub conc?

A

more subs, IROR increases = more subs that can bind to the active site of enzymes

  • (enzyme conc is fixed)
  • at point of velocity max, a plateau is reached as all of the active sites are being used up at once, so IROR can’t increase
72
Q

How does temp acc denature an enzyme?

A
  • shape of active site changes

- due to increased internal vibrations which cause hydrogen bonds within protein to break

73
Q

Q little 10 - the temp co-efficient

A

“for a 10 degrees C rise in temp, the ROR doubles”

74
Q

when Q little 10 does not equal 2:

A
  • q10 only works when molecules are free to move in solution
  • if mols rn’t free to move, Q10 doesn’t work & doesn’t =2
  • E.g. LDRs of photosynthesis
75
Q

what is PH?

A

a measure of hydrogen ion conc

76
Q

why do enzymes only have a narrow PH range?

A
  • active site will only be in right shape a certain H ion conc- this is optimum PH
  • when PH changes, excess or reduction in H ions disrupts 3D shape of the protein, denatured
77
Q

but what if PH changes back?

A
  • if returns to optimum, protein will resume its normal shape and catalyse reactions again - renaturation
  • when PH conc changes more sig, structure is irreversibly altered - no renaturation
78
Q

enzyme e.g. & their optimum PHs?

A
  • pepsin - a protease that works in stomach - PH2
  • salivary amylase - 7 - in mouth
  • arginase - enzyme that works in liver cells - 9.5
79
Q

what is the point of enzyme inhibition?

A

it’s important that the rate of an enzyme catalysed reaction in a cell is controlled/ doesn’t go too fast

80
Q

how does a competitive inhibitor work?

A
  • competitive inhibitor competes with the substrate for the enzyme’s active site
  • ESC can’t form if the enzyme is bound to inhibitor
  • slows ROR
81
Q

why is Vmax still achieved with competitive inhibitor:?:

A
  • eventually the substrate molecule ratio increases, the sub conc becomes so sig comp to competitive inhibitotr conc (fixed), that the comp inhibitor has very little/ no effect on the IROR
82
Q

examples of competitive inhibitiors - statins?

A

inhibit one of the enzymes responsible for production of cholesterol and therefore lowering cholesterol

83
Q

examples of competitive inhibitiors - aspirin?

A

inhibits the production of molecules that cause pain

84
Q

examples of competitive inhibitiors - ethylene glycol poisoning/ anti freeze?

A
  • ethanol is used as the inhibitor
  • ethylene glycol is broken down into oxalic acid by an enzyme in the liver (ethanol hydrogenase).
  • Oxalic acid causes blood acidosis, kidney damage… ethanol slows down reaction,
  • and so liver can detoxify the molecules
85
Q

examples of competitive inhibitiors - why can ethanol be used?

A
  • similar shape to ethylene glycol
  • some short term side effects
    (super vet, icicle)
86
Q

examples of competitive inhibitiors - peniclillin?

A

antibiotic that prevents the formation of bacterial cell walls

87
Q

irreversible inhibitors are often very?

A

toxic, as they can destroy the enzyme they bind to

88
Q

why can V max not be achieved with non comp inhibition?

A

as substarte conc increases, the ratio of inhibitor to enzyme molecules doesn’t change
- so there’s always the same no. of enzyme molecules being inhibited no matter the substrate conc

89
Q

examples of non competitive inhibitors - digoxin?

A

a drug that reduces heat rate and increases force of muscle contraction- extracted from foxgloves

90
Q

example of non competitive inhibitors (farming) ?

A

organophosphate pesticides

91
Q

examples of non competitive inhibitors

A

proton pump inhibitors - treat indigestion

92
Q

difference between serial dilutions and dilution series table?

A

serial dilution - don’t start from stock solution, instead start from previous solution (like compound interest), decrease in conc by a factor of 10 each time
dilution series - always starts from stock solution, a set volume is made up

93
Q

Bio: cofactors description?

A

Usually inorganic small often ions

- bind temporarily to enzyme

94
Q

Bio: cofactors EXAMPLE*

A

CHLORIDE IONS ACT AS COFACTORS FOR SALIVARY AMYLASE

95
Q

Bio: Coenzymes description ?

A

Organic, larger, more complex, often derived from vitamins

Bind temporarily to enzyme

96
Q

Bio: examples of coenzymes *

A

Vitamin B 3

- Vitamins act as coenzymes

97
Q

Bio: prosthetic groups description?

A

Form a permanent part of the enzymes structure

98
Q

Bio: prosthetic groups examples?

A
  • Haem group in Haemoglobin (Haemoglobin isn’t an enzyme tho)
    • Zn 2 plus allow carbonic anhydrase to form carbonic acid from H2O in erythocytes (RBCs)
99
Q

Bio: Inactive precursor molecules?

Pepsinogen

A
  • some enzymes secreted as INACTIVE precursor molecules, especially digestive enzymes that coild harm cells that secrete them
  • these enzymes are activated by other enzymes or a change in PH outside the cell
  • E.g. pepsinogen is an inactive protease released into the stomach. Low PH in stomach activates Pepsinogen turning it into Pepsin

A Level Biology (28 decks)

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