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enzymes and chromatography Flashcards

1
Q

mn what makes up an organisms metabolism?

A

all biochemical reactions in the body

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2
Q

what two types of reaction does metabolism include?

A

anabolic and catabolic

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3
Q

what is an anabolic reaction with examples

A

building up/synthesis
A+B->C
e.g. protein synthesis and photosynthesis

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4
Q

what is a catabolic reaction with examples

A

breaking down/ degradative
C->A+B
e.g. respiration and digestion

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5
Q

how many enzymes may an individual cell contain?
when are they made?

A

1000s
when required

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6
Q

general enzyme equation

A

enzyme+substrate <–> enzyme-substrate complex <–> enzyme-product complex <–>enzyme+product

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7
Q

example of how enzymes affect structure of organisms

A

polymers require enzymes for speedy formation e.g. starch, cellulose, DNA, collagen, muscle fibres

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8
Q

why are enzymes used in organisms rather than chemical catalysts

A

bio reactions wouldn’t occur quickly enough w/o enzymes
chem catalysts require specific conditions of high temps and/or pressure
bio enzymes work under less extreme conditions, so do not affect vital processes

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9
Q

features of enzymes

A

act as biological catalysts
are globular proteins
many end in -ase
possess an active site and can form ESCs
can catalyse forwards/backwards reactions
remain unchanged by reaction they catalyse
v small no. of enzyme molecules are needed
can be inhibited
may be denatured
some require presence of cofactors to function

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10
Q

how do enzymes act as biological catalysts?

A

proteins used in metabolism which speed up the rate of reaction by lowering the activation energy

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11
Q

how are enzymes globular proteins?

A

have precise/specific 3D shape, with polar/hydrophilic R groups pointing outwards and hydrophobic R groups pointing inwards
therefore they are soluble tertiary/quaternary proteins

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12
Q

examples of enzymes that end in -ase

A

lipase
amylase
protease
maltase
catalase
ATPase

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13
Q

what is an enzyme’s active site?

A

a cleft/depression in an enzyme

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14
Q

how does an ESC form

A

temporary bonds form between a substrate and an enzyme’s active site

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15
Q

what is the direction of reaction that an enzyme catalyses determined by?

A

substrate availability and other factors

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16
Q

explain why enzymes remain unchanged by the reaction they catalyse?

A

can be reused
constantly broken down and reformed only when needed

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17
Q

why are there only a very small number of enzyme molecules needed?

A

they can be reused
the rate at which substrate binds and is converted to products is very rapid

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18
Q

types of inhibitors

A

competitive inhibitors
non-competitive inhibitors

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19
Q

what is denaturing?

A

a permanent change in the tertiary and secondary structure of an enzyme

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20
Q

what can enzymes be denatured by?

A

high temperature of extreme pH
(NOT LOW TEMP; THIS ONLY MAKES ENZYMES INACTIVE)

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21
Q

what is a cofactor

A

any substance which is essential for efficient functioning of a enzyme

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22
Q

types of cofactor

A

prosthetic group
inorganic ions
coenzymes

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23
Q

prosthetic group cofactor:
fetaures
examples

A

non-protein part of an enzyme which is tightly bound on a permanent basis
usually metal ions e.g. harm (Fe 2+) found in catalase and zinc (Zn 2+) found in carbonic anhydrase

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24
Q

inorganic ions cofactor:
fetaures
examples

A

not permanently bound, may bind temporarily to an enzymes or substrate
e.g. Cl- for amylase

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25
Q

coenzyme (organic) cofactor:
fetaures
examples

A

bind to active site for short periods/at the same time as the substrate
temporarily bound
carry chemical groups between enzymes e.g. electrons
often vitamins e.g. NAD and FAD derived from vitamin B are involved in respiration
vitamin K involved in blood clotting

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26
Q

how do coenzymes, cofactors and prosthetic groups increase enzyme activity

A

bind to enzyme/AS
cofactors & coenzymes bind temporarily and change the shape of the AS
may affect charges on AS
may bind to substrate
increase likelihood of ESC formation

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27
Q

residues directly involved in enzyme action

A

contact residues
catalytic residues

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28
Q

what do contact residues do?

A

bind to the substrate and therefore it is these residues that determine enzyme specificity

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29
Q

what do catalytic residues do?

A

act on the bonds within the substrate that are broken by enzyme action

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30
Q

function of hydrophobic residues?

A

interact by pointing inwards to maintain the 3D tertiary structure of an enzyme

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31
Q

function of hydrophilic residues?

A

point outwards and maintain the solubility of enzyme so it can move and collide with the substrate

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32
Q

what reactions do intracellular enzymes catalyse?
examples

A

reactions inside the cell
catalase
respiratory enzymes
photosynthetic enzymes
enzymes acting inside nucleus

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33
Q

what is a metabolic pathway?

A

a series of consecutive reactions, every step catalysed by a specific enzyme that produces a specific product

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34
Q

why do endotherms maintain a stable internal temperature?

A

so that optimum temperature is maintained for enzyme activity

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35
Q

where is catalase found

A

liver, potato, yeast
in vesicles in eukaryotic cells called peroxisomes

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36
Q

what is hydrogen peroxide and what does catalase break it down into?

A

a toxic product of many metabolic pathways
catalase breaks it down into water and oxygen

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37
Q

how many reactions can catalase catalyse?

A

6 million per second

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38
Q

reaction for breakdown of hydrogen peroxide

A

H2O2<–>2H2O+O2

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39
Q

catalase primary structure

A

sequence of amino acids joined by peptide bonds

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40
Q

catalase secondary structure

A

folding into alpha helices and beta pleated sheets
held by hydrogen bonds

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41
Q

catalase tertiary structure

A

3D folding of secondary structure into a specific shape
held together by hydrogen bonds, hydrophobic/hydrophilic interactions, ionic bonds and disulphide bonds

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42
Q

catalase quaternary structure

A

more than one polypeptide chain interacting
held together by hydrogen bonds, hydrophobic/hydrophilic interactions, ionic bonds and disulphide bonds

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43
Q

catalase conjugated protein?

A

has 4 ham groups= prosthetic groups (cofactors) which allow it to interact what hydrogen peroxide

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44
Q

what can act as a non-competitive inhibitor of catalase

A

any heavy metal ion e.g. copper
the poison cyanide

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45
Q

what are respiratory enzymes responsible for?

A

the breakdown of glucose and the formation of ATP

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46
Q

examples of respiratory enzymes?

A

phosphorylases
decarboxylases
dehydrogenases
ATP synthase

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47
Q

what do phosphorylase do and where do they act?

A

act in cytoplasm
glucose is phosphorylated to keep it in the cell and make it more reactive

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48
Q

what is phosphorylation?

A

adding a phosphate group (PO4 3-)

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49
Q

what do decarboxylases and dehydrogenases do and where do they act?

A

act in matrix of mitochondria
decarboxylases remove CO2
dehydrogenases remove H2

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50
Q

what does ATP synthase do and where does it act

A

acts on inner mitochondrial membrane
synthesises ATP by converting ADP, Pi and energy to ATP

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51
Q

example of photosynthetic enzymes

A

ribulose biphosphate carboxylase

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52
Q

examples of enzymes acting inside the nucleus and their function

A

DNA polymerase (synthesis of DNA)
RNA polymerase (synthesis of RNA)

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53
Q

what do extracellular enzymes do?

A

catalyse reactions outside the cell

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54
Q

example of extracellular enzyme functioning

A

some organisms e.g. fungi release the enzymes outside their cells and sometimes their whole body e.g. flies, fungal hypha
saprotrophs secrete digestive enzymes from thread-like hyphae and reabsorb digested material
other organisms have internal digestive systems but many of their enzymes act extracellularly

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55
Q

decomposer saprotrophic nutrition example

A

decomposers break down cellulose in dead plants using enzyme cellulase to release beta glucose which they absorb and use for respiration

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56
Q

digestive enzymes in heterotrophs?

A

carbohydrases
proteases
lipases

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57
Q

carbohydrase
example
substrate molecule
bond to break
site of production and action
products

A

amylase
carbohydrate starch
glycosidic
salivary glands & mouth OR pancreas & small intestine
maltose

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58
Q

protease
example
substrate molecule
bond to break
site of production and action
products

A

pepsin
protein
peptide
stomach
peptides

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59
Q

lipase
example
substrate molecule
bond to break
site of production and action
products

A

lipase
lipids
ester
pancreas & small intestine
fatty acids & glycerol

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60
Q

what happens to soluble products of digestion?

A

they can be absorbed via epithelial cells of villi in small intestine

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61
Q

advantage of having an internal digestive system compared with secreting enzymes outside the organism?

A

enzymes not lost to the environment so they can be reused and recycled
internal environment can be regulated to give optimum temperature and pH for enzymes

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62
Q

amylase structure

A

1 polypeptide chain made of 496 amino acids
Cl- (inorganic ion cofactor)
calcium ion (prosthetic group cofactor)

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63
Q

step-by-step lock and key hypothesis

A

1: substrate arrived and collides with active site
2: substrate fits into active site, complementary binding
3: products leave active site
4: enzyme reused

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64
Q

step-by-step induced fit model

A

1: initial binding; temporary bonds form (e.g. H bonds, ionic bonds, hydrophobic/hydrophilic interactions)
2: conformation change in enzyme structure (shape change of active site might put strain on the chemical bonds in the substrate- lowers Ea) (catalytic R groups now interact with substrate and reaction occurs; lowers Ea)

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65
Q

how does the induced fit differ from the lock and key hypothesis?

A

IF: active site changes shape due to bonds acting on it when the substrate enters. once reaction is complete, AS returns to its original shape and next reaction can occur
LK: AS is complementary to substrate. substrate fits into AS like key in lock, no change in shape of AS

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66
Q

hexokinase glucose molecule catalyse

A

glucose induces change in shape in the enzyme
enzyme can enclose substrate to lower activation energy

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67
Q

what is necessary for a reaction to take place?

A

some or all of the chemical bonds need to be broken and new bonds formed

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68
Q

to get the bonds to a state that allows them to break the molecule must be deformed intern unstable state called the what?

A

transition state

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69
Q

what energy is required to reach the transition state?

A

the activation energy: the extra energy needed for the substrate to be converted into products

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70
Q

what can speed up the rate of reaction?
issue with this in living organisms?
how is this overcome?

A

increasing the temperature
there comes a point where further heating causes molecules to denature
they lower the activation energy required
reactions catalysed by enzymes take place at much lower temperatures that they would without them

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71
Q

how do enzymes lower activation energy?

A

1: catalytic R groups might donate or accept electrons or form bonds with substrate (helps substrate reach the transition state)
2: enzyme may create a particular environment by enclosing the substrate e.g. water may be excluded due to hydrophobic environment (or acidic environment)
3: on binding, bonds in the substrate may be strained (stretched/weakened), which will help molecules reach transition state (unstable)
4: enzymes orientate molecules so reacting bonds are near to each other

72
Q

why do reactions begin swiftly as soon as enzymes and substrate Arte mixed and large amounts of oxygen are quickly released?

A

when enzyme and substrate are first mixed, there are large numbers of substrate molecules available.
at any moment, virtually every enzyme has a substrate molecule in its active site

73
Q

why does the rate at which oxygen is released gradually plateau aa reaction continues?

A

rate is prevented from increasing further because fewer and fewer substrate molecules remain to bind with enzyme (limiting factor)
enzymes may be ‘waiting’ for a substrate molecule to hit their AS
increased product molecules get in the way of collision
eventually reaction stops and no more O2 is produced; this is because all substrate molecules have reacted

74
Q

why is rate of an enzyme controlled reaction always fastest at the beginning

A

initial rate of reaction at t=0s
this is used to compare with each value of the independent variable

75
Q

calculation for initial rate of reaction

A

change in y / change in x

76
Q

OCR guidance when drawing tangent

A

draw tangents as long as possible

77
Q

enzymes properties

A

soluble and reactive

78
Q

enzymes structure due to solubility

A

hydrophilic R groups point out
hydrophobic R groups point in
spherical shape (folded)
globular proteins
all have tertiary structure, folding into precise 3D shape (held by H & ionic bonds and hydrophobic/philic interactions)

79
Q

enzymes function which means they must be soluble?

A

enzymes need to be soluble to move around and collide with the substrate in order to catalyse reactions
have specific shape of active site where substrate binds to

80
Q

enzymes structure due to reactivity

A

complementary active site
contact residues
catalytic residues
all have tertiary structure which is precise and specific to substrate
cofactors: inorganic ions, coenzymes, prosthetic groups
induced fit model

81
Q

enzymes function which means that must be reactive

A

catalysts, so must be able to bind specifically to the substrate
put strain on bonds in substrate

82
Q

2 ways to measure rate of enzyme reactions

A

measuring appearance of a product
measuring disappearance of a substrate

83
Q

2 examples of measuring disappearance of a substrate

A

caesin -> amino acids using trypsin
starch -> maltose using amylase

84
Q

where is caesin found and what colour is it

A

milk
white

85
Q

are amino acids soluble or insoluble?
what colour solution do they form?

A

soluble
translucent

86
Q

how to measure disappearance of a substrate to calculate rate of reaction: breakdown of starch to maltose

A

take samples at known intervals and to each sample add iodine in potassium iodide solution
starts blue-black. eventually when all the starch is broken down it would remain brown/orange

87
Q

how to calculate initial rate from starch/maltose disappearance of substrate reaction

A

use a colorimeter to measure the intensity of blue colour and use this as a measure of the concentration of starch remaining, increasing accuracy of determining this
get colorimeter readings for known concentrations and plot a calibration curve
compare your data to thus

88
Q

error that may have resulted form subjectiveness of end point of PAG
improvement and justification for this

A

random errors may lead to inaccuracy/anomalies
colorimeter could be used instead with samples taken at regular intervals
allows quantitative determination of I=end point an should increase the repeatability and precision of the data

89
Q

limitations for catalase practical

A

only 1 measurement taken of volume at each time for each enzyme conc
whole exp. only conducted once
samples may have been take from different sources e.g. different potatoes
pH not kept constant
temp not kept constant
equipment not calibrated properly
low resolution of equipment
no negatives control experiment conducted
SA not controlled
syringe not large enough to collect all gas
difficult to cut all potatoes to same size

90
Q

error of limitation: only 1 measurement taken of vol. at each time at each enzyme conc
improvement and justification

A

unable to identify anomalies and cannot assess precision or repeatability, no mean can be calculated or standard deviation so random errors have large impact on data
take 5 replicates and calc. mean
allows repeatability, precision e.t.c. and increases accuracy of mean, increasing confidence in the trends drawn from the results

91
Q

error of limitation: whole experiment only conducted once
improvement and justification

A

unable to assess reproducibility
repeat whole exp. on a different day or with different people but using same equipment
increased confidence

92
Q

error of limitation: samples may have been from different organisms
improvement and justification

A

different age/variety of environmental state so may introduce random errors
use same tissue source e.g. take smaller cylinders all from same potato or us potato clones
reduces effect of random differences in enzyme conc. of potatoes

93
Q

error of limitation: pH not constant
improvement and justification

A

method not valid: pH change caused by a change in H+ conc. reduces the rate of an enzyme controlled reaction
use pH buffer solution to keep pH constant and use pH probe to check
ensures variables are controlled and that results obtained are valid

94
Q

error of limitation: temp not constant
improvement and justification

A

method not valid. an increase in temp = increase in KE and more ESCs form. high temp denatures enzymes so no ESCs can form
use thermostatically controlled WB before and during reaction
ensures variables are controlled and results obtained are valid

95
Q

error of limitation: equipment not calibrated properly
improvement and justification

A

systematic error due to displacement of air int he tube as syringe is pressed down, giving overestimation of rate
subtract the additional volume from each result. pilot study
ensures errors do not affect rate measurements

96
Q

error of limitation: low resolution of syringe
improvement and justification

A

measurements have high uncertainty
choose equipment with high resolution and low uncertainty e.g. volumetric syringe
gives greater accuracy and precision of measurements

97
Q

error of limitation: no negative control experiment conducted
improvement and justification

A

investigation not valid bc not clear that change in IV has caused change in DV. no baseline or reference value for comparison
conduct a control experiment e..g. boil to denature the enzymes or do without substrate
allows comparison to ensure external factors do not contribute to reaction.

98
Q

error of limitation: SA not controlled
improvement and justification

A

investigation not valid bc SA;vol not controlled, which affects rate bc more molecules exposed
crush up sample to extract the enzyme-containing part and perform serial/proportional dilution to change enzyme conc. keep SA the same
increased validity

99
Q

error of limitation: syringe not big enough to collect all of gas given off
improvement and justification

A

results not accurate bc some of gas not collected so volume collected was underestimated
use bigger/volumetric syringe
increased accuracy

100
Q

why does increasing enzyme conc. increase rate?

A

increased no. of active sites available
increased frequency of successful collisions
increased no. of ESCs formed
increased product formed per second
increased initial rate

101
Q

why does graph of enzyme conc. vs initial rate plateau if substrate conc. is fixed?

A

substrate= limiting factor
if enzyme conc increases further, rate doesn’t increase as there are active sites not occupied by substrate
V max. reached

102
Q

why is enzyme conc. usually low in cells

A

enzymes can be reused
genes for enzymes can be switched on if required

103
Q

why does increasing substrate conc increase initial rate?

A

increased frequency of successful collisions between active sites and substrates
increased no. of ESCs formed
increased product formed per second
increased initial rate

104
Q

at high substrate concentrations with a fixed enzyme rate, rate plateaus because…

A

enzymes reach V max and every AS is occupied
turnover rate for each enzyme= different

105
Q

what is an enzyme’s turnover rate?

A

the number of substrates broken down by a single enzyme per second

106
Q

how to measure rate of breakdown of H2O2

A

measure volume of O2 produced per minute for 5 mins at each IV change
plot on a graph
dare tangents at t=0s
calculate initial rate for each IV change

107
Q

effect of temp below/near freezing on enzymes

A

enzyme is inactivated

108
Q

effect of low temp on enzymes

A

molecules move more slowly so have less KE so have a decreased frequency of successful collisions between AS and substrate so less ESCs are formed, decreasing rate

109
Q

effect of increasing temp on enzymes

A

increased KE so increased frequency if successful collisions between AS and substrate so increased ESCs form, increasing rate
up to optimum, where there is the highest initial rate (V max)

110
Q

what is Q10

A

temperature coefficient
a way of quantifying the effect of temp on the rate of reaction
the factor by which the rate increases for a 10C rise in temp

111
Q

Q10 formula

A

rate at t +10C / rate at t

112
Q

what is the value for Q10 in an enzyme reaction?
why?

A

taken as two
rate of reaction doubles with a 10C rise in temp (below the optimum)

113
Q

above optimum temperature, what happens to rate of reaction as temp increases?

A

rate drops sharply
increasing temp causes molecules to vibrate more
initially, enzyme just starts to change shape, decreasing frequency of successful collisions (enzymes not yet denatured)
more vibrations can break H and ionic bonds
loss of 2ary and 3ary structure
(peptide bonds/1ary structure not broken)
AS changes shape and is no longer complementary to substrate
enzyme function is not restored

114
Q

what is denaturing?

A

complete, irreversible change in the shape of an enzyme’s active site so it is no longer complementary to the substrate
rate = 0

115
Q

effect of pH on enzymes

A

enzymes work within narrow ranges of pH
small changes either side of optimum pH decrease rate bc shape of AS is disrupted BUT NOT DENATURED
at extreme changes from optimum pH, ENZYME DENATURES so rate=0

116
Q

how do changes from optimum pH affect enzyme structure? ACIDS

A

acids= proton donors
protons are attracted to - charged ions/molecules/R groups
excess H+ interfere with H and ionic bonds
can cause 2ary and 3ary structure to unravel
AS changes shape
substrate molecule no longer fits
CAN also alter charges on AS so more protons cluster around - charge R groups and stop substrate bonding

117
Q

how do changes form optimum pH affect enzyme structure? ALKALI

A

base= proton/H+ acceptor
pos. charged ions/molecules/R groups accept a H+, lose charge and cannot form H/ionic bonds anymore
2ary and 3ary structure unravel
AS changes shape
substrate molecule no longer fits

118
Q

what is a buffer?

A

a chemical substance that resists large changes in pH

119
Q

types of enzyme inhibitors

A

competitive inhibitor
non-competitive inhibitor
end product inhibition

120
Q

what do enzyme inhibitors do?

A

reduce are of enzyme-controlled fractions bc they have an effect on the enzyme molecule

121
Q

competitive inhibitors:
structure
how they work
reversible/irreversible?
effect of increasing substrate conc.

A

have close structural resemblance to substrate of an enzyme
compete with substrate for active site
mostly reversible, and if binding irreversibly they are called inactivators
increasing substrate conc relative to inhibitor conc increases initial rate

122
Q

example of competitive inhibitor
what enzyme does it inhibit? what is this enzyme’s function
function and use

A

statins
HMG-coA reductase (makes cholesterol in liver)
treats people with CHD as it decreases fatty deposit in arteries bc it decreases cholesterol production

123
Q

non competitive inhibitors
structure?
where does it bind to?
how does it work?

A

no structural similarity to substrate (not competing with it for AS)
binds to allosteric site of enzyme (not AS)
distorts active site: conformational change in AS (change to 3ary structure) so is no longer complementary to substrate
equal affinity for enzyme and ESC

124
Q

increasing substrate conc with a NC inhibitor…

A

doesn’t affect rate of reaction bc enzymes can be inhibited regardless of how saturated their active sites are (NC inhibitor can bind to enzyme regardless of if substrate has already bound. once bounds, enzyme cannot catalyse its substrate)

125
Q

will a reaction reach its normal V max with a NC inhibitor?
what is this V max determined by?

A

no
subset of enzyme molecules will always be inactivated by inhibitor bc it can bind to enzymes regardless of whether they are bound to a substrate or not
lowers conc. of usable enzyme so lowers V max
conc. of inhibitor

126
Q

when NC inhibitor saturation is reached, the rate of reaction is….

A

almost 0
bc all bound to enzymes

127
Q

example of NC inhibitor
enzyme it inhibits
inhibitor function

A

cyanide (poison)
respiratory enzyme cytochrome oxidase
prevents formation of ATP
particularly dangerous bc it binds irreversibly

128
Q

COMPETITIVE vs NON-COMPETITIVE inhibitors: reversible or irreversible

A

most competitive inhibitors do not bind permanently to AS (reversible); they bind for short period the leave. removal of inhibitor from reaction mixture leaves enzyme molecule unaffected
many non-competitive inhibitors bind permanently to enzyme molecules. inhibtion cannot be reversed and any molecules bound by inhibitor are inactivated

129
Q

examples of positive inhibition

A

statins
naloxone

130
Q

why is initial rate of reaction lower at low substrate concs when competitive inhibitor is added

A

some enzymes are bound to inhibitors at low substrate conc.

131
Q

can the normal V max be reached with a competitive inhibitor?

A

yes it is possible at v high substrate concs
all AS bound to substrate at start

132
Q

why does initial rate increase as substrate conc increases with non competitive inhibitor

A

some AS that have not changed shape as not bound to inhibitor but could not bind to substrate at low substrate conc as there were not enough
these AS are filled as substrate conc increases so rate increases

133
Q

what is negative feedback?

A

change away from set point (e.g. conc of product) that leads to a reversal of this change

134
Q

example of negative feedback?

A

end-product inhibition (end product of multienzyme complex inhibits an enzyme in a step of its synthesis to prevent further synthesis of itself)

135
Q

why is product inhibition useful?

A

no over production, which could be a waste of resources
reversible, so low product amount means low inhibition

136
Q

what is a multi enzyme complex?
usefulness
where do they take place

A

stable assembly of more than 1 enzyme
increase efficiency of metabolic reactions as they keep enzymes and substrate in same location (less diffusion needed)
some enzymes found close together in membrane so work together in multi-step reaction

137
Q

why are some enzymes synthesised as inactive precursors in metabolic pathways?

A

prevent damage to cells producing them

138
Q

how do inactive precursors work?

A

part of precursor molecule inhibits enzyme action. once this part is removed, the enzyme becomes active
sometimes changes in pH or temp or addition of cofactor can change 3ary stricture and activate precursor enzyme

139
Q

example of inactive enzyme precursor
why is it synthesised in its inactive form?

A

pepsinogen (inactive) –> pepsin (active) in low pH environments (stomach HCl)
proteases are synthesised as inactive precursors to prevent damage to proteins in the cell

140
Q

how does activation of inactive precursors by addition of cofactor work?
example process

A

apoenzyme (inactive precursor) + FAD/NAD (cofactor/coenzyme activator) -> holoenzyme (active)
cofactor fits into part of active site, without it, enzyme is unactivated and substrate cannot fit

141
Q

example of cascade system of activation

A

BLOOD CLOTTING
platelets-> aggregated proteins release vit.K (cofactor for thromboplastin)
|->prothrombin -> thrombin
|->fibrinogen -> fibrin (formed mesh which traps RBC to form clot)

142
Q

3 examples of metabolic poisons that act as enzyme inhibitors

A

cyanide
snake venom
malonate

143
Q

CYANIDE/CN- ions
enzyme affected?
mechanism

A

cytochrome oxidase (final enzyme in aerobic respiration)
non-reversible inhibitor
aerobic resp. stops

144
Q

SNAKE VENOM
enzyme affected
mechanism

A

acetyl cholinesterase (enzyme which breaks down neurotransmitters)
stops NT being broken down->constant muscle contraction->fatigue->paralysis->suffocation

145
Q

MALONATE
enzyme affected
mechanism

A

inhibits succinate dehydrogenase
competitive inhibition of respiratory enzyme

146
Q

6 examples of medicinal drugs that act as enzyme inhibitors

A

apsirin
cardiac glycosides
ACE inhibitors
protease inhibitors
nucleoside reverse transcriptase inhibitors
proton pump inhibitors

147
Q

ASPIRIN
enzyme affected
mechanism/use
why should children not take aspirin?

A

enzymes that form prostaglandins which are produced when tissues are damaged
PG make nerve cells more sensitive to pain and increase swelling
less PG means less pain
can reduce risk of blood clots forming in blood vessels and strokes
can damage children stomach lining

148
Q

CARDIAC GLYCOSIDES
examples
enzyme affected
mechanism/use

A

digitalis, digitoxin, digitalin, digoxin
ATPase (less ATP production with digitalis)
less ATP means Na+/K+ pumps in cell membrane of heart muscle cells are inhibited
more Ca2+ can enter cells and this increases contraction, strengthening heartbeat

149
Q

ACE INHIBITORS
enzyme affected
mechanism/use

A

angiotensin converting enzyme which normally increases BP
lowers BP in patients with hypertension(high BP) who cannot take beta-blockers
treat heart failure
minimise risk of 2nd heart attack or stroke

150
Q

PROTEASE INHIBITORS
examples
enzyme affected
mechanism/use

A

ritonavir and amprenavir
protease
prevent replication of virus particles inside host cells as protein coat cannot be made
competitive inhibition

151
Q

NUCLEOSIDE REVERSE TRANSCRIPTASE INHIBITORS
examples
enzyme affected
mechanism/use

A

zidovudine and abacavir (treat HIV+ patients)
nucleoside reverse transcriptase
inhibit enzyme involved in making DNA using viral RNA as a template

152
Q

PROTON PUMP INHIBITORS
enzyme affected
mechanism/ use

A

block H+/K+ ATPase enzyme that secretes H+ into the stomach
reduce production of excess stomach acid to prevent ulcers

153
Q

what is chromatography an example of?

A

a separation technique

154
Q

what can chromatography be used to separate

A

biological molecules e.g. amino acids, carbohydrates, nucleic acids in a mixture

155
Q

the 2 types of chromatography

A

thin layer chromatography
paper chromatography

156
Q

what is the stationary phase of chromatography?
what is it in TLC and paper chromatography?
property of stationary phase?

A

where the molecules cannot move
TLC plate: sheet of plastic coated with silica gel or aluminium hydroxide (adsorbent)
paper: made of cellulose
VERY POLAR

157
Q

what is the mobile phase of chromatography?
examples and types
properties
what does it do?

A

where the molecules can move
solvent:
water (for polar molecules)
hexane, organic solvent, alcohols (e.g. ethanol, butan-1-ol) (for non-polar molecules)
flows over stationary phase carrying biological molecules with it

158
Q

calculation for retention factor?

A
159
Q

chromatography: what do amino acids separate out based on?

A

their solubility in solvent
adsorption to plate
size
polarity

160
Q

stationary phase property and what does this mean?

A

VERY POLAR
hydrogen bonds form between the molecules and the paper (adsorption)

161
Q

what is adsorption?

A

adhesion of atoms from a gas/liquid/solid onto a surface

162
Q

what is the running solvent in chromatography usually a mixture of?
therefore what property does it have

A

butan-1-ol
ethanoic acid
water
RELATIVELY NON-POLAR

163
Q

why do amino acids vary in polarity?

A

due to their different R groups

164
Q

highly polar amino acids do what during a chromatography experiment?
why?

A

stick/adsorb to surface more and move slowly up plate
least soluble in non-polar solvent & more attracted to polar plate

165
Q

less polar amino acids do what in a chromatography experiment?
why?

A

travel furthest
most soluble in non-polar solvent and less attracted to polar plate

166
Q

how to carry out chromatography with amino acid sample due to their colourless property?

A

cannot see samples as they rise up paper
chemical is used to develop chromatogram
ninhydrin is sprayed on the paper after it has been allowed to dry
purple/brown spot appears, showing the location of the samples

167
Q

use of reference materials in chromatography?

A

testing a sample alongside a set of reference samples can be used to identify the chemicals present
spots in the sample can be compared with spots from the known reference samples
or the Rf values can be compared with a reference table

168
Q

why is the same Rf value as a reference sample not always achieved?

A

TLC plate/ paper might be different
different concentration of solvent
different size of plate
different temperature
may have used a different solvent

169
Q

what do a high and low Rf value mean?

A

low Rf value means sample has moved a short distance
high Rf value means sample has moved a longer distance

170
Q

example of a highly polar and less polar amino acid

A

aspartic acid/ glutamate
leucine

171
Q

are paper and TLC qualitative or quantitative analyses?
why?

A

QUALITITATIVE
they don’t show how much of a chemical is present- instead they just show what is or isn’t present

172
Q

advantages of TLC compared to paper chromatography

A

TLC gives better results for a wider range of chemicals
TLC is quicker, more sensitive and produces a clearer separation so it is easier to analyse

173
Q

what is a TLC plate?

A

a sheet of glass coated with a thin layer of solid adsorbent, usually silica (polar)

174
Q

equipment that could be used to accurately measure the volume of 1cm3 an enzyme solution

A

1cm3 syringe
volumetric pipette
graduated teat pipette

175
Q

how does variegin (competitive inhibitor of thrombin) act as an inhibitor?

A

thrombin converts fibrinogen to fibrin
variegin has a similar shape to fibrinogen
so can occupy the active site of thrombin enzyme
variegin prevents fibrinogen binding to the active site/ enzyme-substrate complex formation
slower rate of conversion of fibrinogen to fibrin
action of variegin not permanent/ temporary

176
Q

things to talk about whenadating procedures of experiments

A

APPARATUS AND METHOD e.g. test tubes, apparatus for volume measurements, distilled water, water bath, stopclock/timer, details of quantitative preparation
VARIABLES e.g. independent, dependent, units used, control variables
REPEATABILITY e.g. repeats for each change in independent variable, quantitative processing of data e.g. means
RISK ASSESSMENT e.g. potential chemical hazards and control, potential electrical hazards and control

biology (28 decks)

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