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A Level Biology > Enzymes > Flashcards

Enzymes Flashcards

1
Q

what type of protein are enzymes

A

globular

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2
Q

how do enzymes increase the rate of a reaction?

A

lowers the activation energy, by e.g bringing reactants together to react

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3
Q

True or False unwanted products are produced by enzymes

A

false

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4
Q

How can cells regulate how quickly enzymes catalyze a reaction

A

increase/decrease the number of enzymes catalyzing the reaction = faster/slower reaction

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5
Q

define an enzyme

A

biological catalysts (1) that speed up the rate of reaction (2)in living organisms (3)

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6
Q

turnover number meaning

A

no. of reactions an enzyme can catalyse per second

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7
Q

The greater the activation energy needed the …. rate of of reaction. FIll in the blank

A

slower

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8
Q

What 2 things are needed for a reaction with an enzyme to occur

A
  • collision of substrate & enzyme

- activation energy

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9
Q

how do enzymes reduce the activation energy

A

By straining the bonds in the susbtrate

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10
Q

intracellular enzymes

A

enzymes that work on the inside of a cell

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11
Q

extracellular enzyme

A

enzymes are released from the cell, to work outside the cell

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12
Q

extracellular enzymes example & use (1)

A

amylase digests starch into maltose

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13
Q

eexample of an extracellular enzyme & it’s use

A

trypsin breaks down protein s into smaller peptides

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14
Q

name 2 extracellular enzymes

A

amylase, tripase

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15
Q

name a intracellular enzyme

A

catalase

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16
Q

what is a intermediate molecule

A

formed from 2 or more substrates after being catalysed, then react further to give products

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17
Q

what is an enzyme substrate complex

A

enzyme molecule with substrate molecule in it’s actiev site, temporarily joined by non-covalent attraction. BEFORE reaction

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18
Q

what is an enzyme product complex

A

enzyme molecule with product molecule in it’s active site, temporarily joined by non-covalent attraction. AFTER reaction

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19
Q

what is the main suggestion that induced model makes that’s different from lock and key model

A

suggests active site isn’t a rigid structure

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20
Q

what bonds are present in the enzyme-substrate complex (in induced fit model)

A

hydrogen bonds, hydrophobic interactions ionic interactions, Van der Waals forces

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21
Q

what is different in the induced model to lock and key in terms of substrate bonding?

A
  • subtle changes on amino acid’s R-Groups allows substrate to bond more effectively
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22
Q

what is different in the induced model after reaction?

A
  • after reaction, products shape is slightly different to active site & can detach
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23
Q

what happens when pH changes & what effect does it have on the rate of enzyme activity

A

increase/ decrease in H+ ions from the optimum decreases the rate of reaction

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24
Q

how does H+ ions impact protein? (2)

A
  • interferes with hydrogen and ionic bonding (due to charges) = disrupts the tertiary structure
  • alters active site charges = substrate can’t bind
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25
Q

true or false not all enzymes have the same optimum pH?

A

true

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26
Q

true or false not all enzymes have the same optimum temperature?

A

false within THE SAME organism (37C body temperature)

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27
Q

optimum temperature defintiion

A

the temp at which the enzymes have the maximum rate of enzyme acticity

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28
Q

what are buffer solutions

A

solution that resist changes in pH by donating and accepting H+ ions e.g haemoglobin

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29
Q

what is the excess effect of temperature on enzymes

A

breaks hydrogen bonding holding tertiary structure.

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30
Q

does priomary structure of enzyme change by increase/decrease in tmeperature

A

no, peptide binds aren’t affected

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31
Q

what is the effect of temperature on enzymes

A

causes molecules to move faster; increases rate of collision & force with which they collide

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32
Q

what is the temperature coefficient

A

the temperature coefficient of a reaction measure of how much the rate of reactions increases with a 10C rise in temperature.

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33
Q

what is the effect of increasing substrate concentration BEFORE MAXIMUM RATE

A

increase in frequency of collusuons = more ES complexes are made = more product formed

34
Q

what is the effect of increasing substrate concentration AFTER MAXIMUM RATE

A

when all active sites are occupied & ES complexes are made as fast as possible. At this point ENZYME concentration is limiting factor

35
Q

what is the effect of increasing enzyme concentration BEFORE MAXIMUM RATE

A

increase in frequency of collusuons = more ES complexes are made = more product formed

36
Q

what is the effect of increasing enzyme concentration AFTER MAXIMUM RATE

A

all subrate molecules will be occupying an active site & extra enzymes will have empty active sites. At this point SUBSTARTE conrecnteation is limiting factor

37
Q

what does enzyme concentration in a cell depend on of a specicif enzyme(2)

A

rate of synthesis (1) and rate of enzyme degradation (2). (Controlled by coding genes & whether they are on or off.)

38
Q

thw inital reaction rate is the ___ reaction rate for an enzyme

A

thw inital reaction rate is the MAXIMUM reaction rate for an enzyme

39
Q

what are prosthetic groups

A

non-protein component (1) that forms a permanent part (2)of a functioning protein molecule (3)

40
Q

are prosthetic groups tempeoraily bound, or permanelty bond to enzyme or can ethy be either?

A

permanelty bound to enzyme

41
Q

give an example of a prosethic group & for the enzyme it’s binded to

A

Zn2+ ion bound to carbonic anhydrase found in red blood cells.

42
Q

What is carbonic anhydrase

A

a protein with a prosthetic group (1) found in red blood cells (2) catalyses CO2 + H2O reaction into carbonic acid

43
Q

what is a cofactor

A

a substance that has to be present in an enzyme-catalysed reaction for it to take place at an appropriate rate.

44
Q

How does a cofactor ease enzyme-substrate complex formation(2)

A

joins with the substrate to form the correct shape for the active site (1)
change charge distributions on enzyme/substrate surface = easier for enzyme & substate to form temporary bonds

45
Q

what is a coenzyme?

A

small organic (1) non-protein molecule (2) that binds temporarily to active site of enzymes (3)

46
Q

True or False coenzymes are used up in reactions with enzymes? if not what happens instead?

A

false; coenzymes are chemically changed during reaction and need to be recycled to orginal state by another enzyme

47
Q

which of these are derived from water-solublevitamins: prosthetic group, coenzyme, cofactor?

A

coenzyme

48
Q

give an example of coenzyme and where it is derived from? if there’s a deficiency of this vitamin what happens

A

NAD and NADP come from water-soluble vitamin Nicotinamide B3; deficieny causes pellagra

49
Q

what is a competitve inhibitor

A

has a similar shape to substrate (1) and competes for COMPLEMENTARY enzymes active site

50
Q

what impact does a competitive inhibitor have on the rate of reaction and why?

A

decreases activity of enzyme; by blocking the active site (1) preventing ES complexes from forming (2)

51
Q

for which of these does an increase in substrate concentration NOT cause ‘inhibitor rate’ to increase: competitive inhibitors or non-competitive inhibitors

A

non-competitive inhibitors (see graph)

52
Q

what is the competitive inhibitor called if it binds irreversibly to enzyme?

A

inactivator - only happens with few inhibitors

53
Q

how soes a comeptitve inhibitor work?

A

reduces rate of ES compelxes formation (1) forms an ENZYME-INHIBITOR complex that s CATALYCTICALLY INACTIVE

54
Q

true or false most competitve inhibitors reactions with enzymes are reversuble

A

true

55
Q

example of comepeitve inhibitor & for what?

A

statins are competitive inhibitors for cholesterol synthesis

56
Q

defintiton of non-competitive inhibition (4)

A

attaches to the ALLOSTERIC site of an enzyme (1)which causes the shape of its actiev site to change (2) by disrputing its tertiary structure (3) hence ES complex can no longer form (4)

57
Q

true or false non compeittive inhibitors all bind reversibly to enzyme

A

false some bind reversibly some bind irreversily

58
Q

give 2 example of a non-competitive inhibition

A

organophosphates in insecticides and herbicides irreversibly inhibit enzyme acetyl cholinesterase; used in nerve impulse transmission
ATP production in respiration

59
Q

precursor definition

A

enzymes which must be activated to catalyze reactions.(1) Another enzyme removes part of the molecule allowing the active site to assume the correct shape

60
Q

what is the point of precursor enzymes

A

they are mainly digestive enzymes so they don’t digest any of the cells molecules; must be activated first

61
Q

give an 2 examples of precursoes and what they are ‘activated’ to become

A

trypsinogen —> trypsin

pepsinogen —>pepsin

62
Q

end-product inhibition

A

the product of a reaction inhibits the enzyme recquires for the reaction (1) by negative feedback loop (2) to control metabolic pathways (3)

63
Q

what are the advantages of having an end product inhibition system?

A

multi-enzyme complexes increases efficiency, without increasing substrate concentration

64
Q

how does end product inhibition sytem improve efficiency

A

keeps enzyme & substrate in the same area = reduces diffusion time

65
Q

name an example of an enzyme inhibitor poison

A

cyanide

66
Q

how is cyanide poisonous?

A

when hydrolysed, dissociates into CN- and H+ ions, (1) CN-binds irreversibly to an enzyme in mitochondria to inhibit aerobic respiration (2)

67
Q

name an example of a medical drug enzyme inhibitor

A

aspirin

68
Q

what does aspirin do?

A

aspirin reduces inflammation, blood clots in b.vesssels & strokes, by preventing hyper cell signalling from damages/infected tissue cells.

69
Q

how does aspirin work?

A

aspirin hydrolyses into salicyclic acid, which binds to PROSTAGLANDINS enzyme & changes its shape; PROSTAGLANDINS are cell signalling molecules produced when by damaged/infected tissue cells

70
Q

what is the difference ebtween venom and poisons

A

venom - injected into victim (e.g snake bite)

posions - injested toxins

71
Q

what is anabolism

A

anabolism is building of molecules

72
Q

catabolism definition

A

breaking down of molecuels

73
Q

how does anabolism and catabolism relate to metabolism

A

metabolism is the sum of all reactions; including anabolism and catabolism

74
Q

definition of a model e.g induced fit model

A

simple / easy to understand (1); representation (1)

75
Q

Is the Induced fit active site complementary to substrate

A

NO, it is flexible, changes shape as substrate binds for a closer fit

76
Q

why do models change over time (4)

A 
Idea of improved technology (1); idea of continually investigated (1); more evidence (1); more
accurate representation (1)
77
Q

explain denatured (4)

A

R-GROUP INTERACTIONS are disrupted (1); change in tertiary structure (1); change in 3D shape of active
site preventing binding with substrate (1).

78
Q

True or false enzymes denature at extreme low temperatures to their optimum

A

false; low temperatures causes slower rate of enzyme activity

79
Q

why will increasing substrate concentration not affect Vmax when non-competitive inhibitor is present

A

Inhibitor will always be present (1); some enzymes always inhibited (1).

80
Q

what is Vmax

A

the fastest rate of reaction for an enzyme

81
Q

difference between coenzyme and prosthetic group

A

coenzyme binds temporarily, prosthetic is a permanent part of the enzyme

A Level Biology (12 decks)

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