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Biology > 1.4 enzymes > Flashcards

1.4 enzymes Flashcards

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1
Q

key enzyme facts

A

-they’re not used in chemical reactions
- they’re not changed
- they have a high turnover
- enzyme reactions have limiting factors
-specific

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2
Q

what does having a high turnover mean

A

they catalyse many reactions per second

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3
Q

what do we need enzyme reactions for

A

metabolism
(all reactions in the body)

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4
Q

structure of an enzyme

A

tertiary proteins, globular, metabolic functions

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5
Q

what is a biochemical/metabolic pathway

A

a sequence of enzyme-controlled reactions in which a product of one reaction is a reactant in the next

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6
Q

what does anabolic mean

A

building up molecules
(protein synthesis)

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7
Q

what does catabolic mean

A

breaking down molecules
(digestion)

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8
Q

what is activation energy

A

the energy needed to start chemical reactions

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9
Q

what doe enzymes do to the activation energy

A

they lower the activation energy, we don’t need heat for the reactions to occur

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10
Q

what do enzymes do to chemical reactions

A

they act as catalysts by lowering the activation energy needed to drive the reaction

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11
Q

where is lysozyme found and what is it an example of

A

found in tears, its secreted by many different cells and it breaks down bacterial cell walls
an example of the induced-fit model

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12
Q

what is successful collision

A

where the substrate collides with the active site

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13
Q

two types of enzymes

A

-intracellular
-extracellular

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14
Q

what does intracellular mean and an example of one

A

working within the cell
catalase

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15
Q

what does extracellular mean and an example of it

A

working outside the cell
digestive enzymes

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16
Q

what does the lock and key hypothesis suggest

A

that there is an exact fit between the substrate and the active site of the enzyme

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17
Q

explain induced fit hypothesis

A

the active site is not the right shape to begin with. substrate molecule changes the shape of the active site to fit the substrate molecule perfectly
a substrate can mold the enzyme to its own shape so several substrates can react with the same enzyme

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18
Q

what bonds help to maintain the 3D globular shape of the enzyme

A

disulphide bonds, helps maintain the active site

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19
Q

what does the substrate have

A

a complimentary shape that fits into the active site

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20
Q

why is it important that enzymes are efficient

A

because they have a high turnover number which means they can convert many molecules of substrate into product per unit time.

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21
Q

what factors affect enzyme activity

A

temperature/pH/substrate concentration/enzyme concentration

22
Q

how does an temperature affect enzyme activity

A

an increase in temperature gives molecules greater kinetic energy so enzyme and substrate molecules move around more quickly. this increases the chance of collision and will lead to more successful enzyme-substrate complexes. therefore increases the rate of reaction

23
Q

optimum temperature for most enzymes?

A

40

24
Q

what can happen with changes to the pH

A

small changes can affect the rate of reaction without affecting enzyme structure, but small changes outside the optimum range can cause reversible changes in the enzyme structure.
extremes of pH can denature an enzyme

25
Q

how does enzyme concentration and substrate concentration affect rate of reaction
when will the reaction level off

A

if the enzyme concentration remains constant the rate of reaction will increase as the substrate concentration increases. it will level off once all the active sites are occupied, the number of available active sites become a limiting factor at higher substrate concentrations.

26
Q

explain how the substrate concentration being the limiting factor can change
(in terms of a graph)

A

initially the substrate concentration is the limiting factor, when the curve levels off the substrate is no longer limiting the rate of reaction, another factor will be the limiting factor (enzyme concentration)

27
Q

what happens when enzyme concentration becomes a limiting factor

A

all the active sites are occupied, having formed successful enzyme-substrate complexes

28
Q

what is the turnover number

A

the number of molecules that one enzyme molecule can turn into products in a given time

29
Q

what happens as enzyme concentration increases

A

there are more active sites available and therefore the rate of reaction increases

30
Q

what is a limiting factor

A

when an increase in its value causes an increase in the rate of reaction

31
Q

how can you keep temperature constant

A

use an electronic thermostatically controlled water bath

32
Q

what is Vmax

A

is the maximum velocity or rate of reaction for an enzyme

33
Q

what does a higher concentration of enzyme mean

A

would mean a higher overall rate of reaction. the initial rate would be faster and it would level off at a higher point

34
Q

what does a lower concentration mean

A

a reduced rte of reaction. the initial rate would be slower and it would level off at a lower rate

35
Q

what is an enzyme inhibitor
2 types?

A

any substance which decreases the rate of an enzyme catalysed reaction or that stops it
competitive/non-competitive

36
Q

how does a competitive inhibitor work

A

They are structurally similar to the substrate molecule. it can fit in the active site of the substrate molecule. a competitive inhibitor prevents enzyme-substrate complexes forming.

37
Q

what will increasing the substrate concentration
do in the presence of a competitive inhibitor?

A

will decrease the effect of the inhibitor as the enzyme is more likely to collide with a substrate molecule and form a successful enzyme-substrate complex

38
Q

what do non-competitive inhibitors do

A

they don’t bind to the active site, they bind to other parts of the enzyme. this alters the overall shape of the enzyme molecule including the active site. the substrate molecule can no longer fit into the active site

39
Q

what will increasing the substrate concentration do?
(non-competitive inhibitors)

A

it won’t increase the rate of reaction in this case as the substrate can no longer fit into the enzyme’s active site. so successful enzyme-substrate complexes cannot form

40
Q

example of a non-competitive inhibitor

A

cyanide

41
Q

what is the area of the enzyme that is not the active site called?

A

allosteric region

42
Q

what will happen to the rate of reaction with non-competitive inhibitors

A

the enzymes active sites are now the wrong shape, the max rate of reaction falls because the concentration of active enzyme has been reduced

43
Q

what is end-product inhibition

A

where the final product in the pathway inhibits an early-stage enzyme

44
Q

what is the effect of end-product inhibition

A

reduces the rate of the metabolic pathway

45
Q

role of immobilised enzymes

A

to restrict enzyme mobility in a fixed space

46
Q

definition of an immobilised enzyme

A

enzyme molecule bound to an inert material over which the substrate molecules move

47
Q

properties of immobilised enzyme
example of one

A

fixed on a inert matrix
alginate beads

48
Q

benefits of immobilising enzymes
(any4)

A

1-enzyme doesn’t contaminate the product
2-immobilised enzyme can be reused
3-only a small quantity of an enzyme is needed
4- enzymes are more stable
5-can catalyse reactions over a wider range of pH
6- more than one enzyme can be used
7- greater control over the enzyme
8-can be used in a continuous process
9-easy to purify product

49
Q

what does a biosensor do? how are enzymes involved?

A

gives an indication of how much chemical is in the blood/urine (glucose) even at low concentrations
uses enzymes to detect the presence of tiny quantities of specific enzymes

50
Q

what is a transducer

A

it can convert energy from one form to another, it detects chemical energy when substrate is broken down by an enzyme

51
Q

explain how a biosensor will work

A

they use immobilised enzymes on age membrane. the biosensor detects a chemical change, a substrate is converted to product, and a transducer converts this chemical change into an electrical signal which can be amplified and viewed on display

Biology (12 decks)

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