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biology a level OCR > enzymes > Flashcards

enzymes Flashcards

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1
Q

name 8 features of enzymes

A
  • they act as biological catalysts (not used up in a reaction)
  • all enzymes are globular proteins
  • enzymes posses an active site and can form enzyme substrate complexes
  • enzymes can catalyse forward or backward reactions (reversible)
  • enzymes can remain unchanged by the reaction they catalyse
  • only a very small number of enzyme molecules are needed
  • enzymes can be inhibited
  • enzymes may be denatured
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2
Q

know the role of amino acids in enzymes

A

Enzymes are proteins comprised of amino acids linked together in one or more polypeptide chains. This sequence of amino acids in a polypeptide chain is called the primary structure. This, in turn, determines the three-dimensional structure of the enzyme, including the shape of the active site.

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3
Q

what do many enzymes end in

A

ase
- E.g. catalyse, maltase

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4
Q

what part fits into the active site of an enzyme

A

the substrate

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5
Q

what are the two enzyme fit theories

A
  • lock and key
  • induced fit theory
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6
Q

intracellular enzyme action

A

inside the cell

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7
Q

what do enzymes do

A

they speed up the rate of reaction by being catalyst, by reducing the activation energy

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8
Q

what does catalyse break hydrogen peroxide down to

A

oxygen and water

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9
Q

what is extracellular enzyme action

A

the enzyme, is used outside of the cell it was made

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10
Q

what is the structure of globular proteins

A

hydrophobic amino acids surrounded by hydrophilic amino acids
- remember this is why they are soluble in water

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11
Q

what is the enzyme substrate complex

A

The enzyme substrate complex is a temporary molecule formed when an enzyme comes into perfect contact with its substrate

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12
Q

what do we call the active sites bond to the substrate

A

specific/complementary fit

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13
Q

why is the activation energy important

A

it must be reached in order for a reaction to take place, in order to form a product

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14
Q

what does the tertiary structure do in order to form the active site?

A

it folds, in order to form a three dimensional shape

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15
Q

what has to happen, in order to produce product

A

the a substrate must successfully react with the active site.

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16
Q

what dictates the rate of an enzyme controlled reaction

A

the frequency of successful collisions between the substrate molecules and the active site

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17
Q

why is temperature important, in enzyme controlled reactions

A

to high a temperature will lead to the enzyme denaturing due to there being to much kinetic energy causing vibrations, that would sperate the tertiary structure bonds, whilst too low of a temperature would mean that there would be a to little kinetic energy, resulting in a low rate of reaction

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18
Q

what happens at the optimum temperature

A

we have the maximum frequency of successful collisions between the substrate and the active site

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19
Q

can we reactivate denatured enzymes

A

NO

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20
Q

how do we work out Q10 and what value is Q10 normally

A

it is normally a value of around 1, but only below the optimum temperature of the enzyme

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21
Q

how can we contour act the impact of a competitive inhibitor

A

by increasing the substrate concentration

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22
Q

how does one, lower the activation energy

A

by using enzymes ( as a biological catalyst)

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23
Q
  • what is the equation for initial rate
    and
  • how is calculated
A
  • change in y/ change in x
  • by drawing a tangent at time= zero
24
Q

why does increasing enzyme concentration increase rate?

A
  • more active sites available
  • more frequent collisions
  • more enzyme substrate complexes formed
  • greater rate, due to more product being formed per second
25
Q

what is a control variable

A

A control variable is anything that is held constant or limited in a research study

26
Q

effect of increasing substrate concentration

A
  • more successful collisions (between active site and substrate
  • more enzyme substrate complex’s formed
  • greater rate, due to more product being made per second
27
Q

what is a buffer

A

chemicals, that are resistant to a change in pH

28
Q

what doe enzyme inhibitors do?

A

reduce the rate of enzyme controlled reactions because they have an effect on enzyme molecules

29
Q

what is a competitive inhibitor

A

mostly reversible and if binding irreversibly they are called inactivators

30
Q

what are 3 key things about competitive inhibitors

A
  • have close structural resemblance to substrate of enzyme
  • compete with substrate for active site
  • increasing substrate conc, relative to inhibitor conc, then the initial rate increases
31
Q

give one example of a competitive inhibitor

A

statins, a drug used to treat coronary heart disease

32
Q

what is a non - competitive inhibitor

A

does not compete for the active site it has equal affinity (willingness to bind) for the enzyme and enzyme substrate complex

33
Q

what are the 5 key things about non - competitive inhibitors

A
  • it has no structural similarity to the substrate
  • combines with enzyme at a point other than active site (allosteric active site)
  • active site becomes distorted (substrate no longer fits)
  • when inhibitor saturation is reached the rate of reaction is almost nil
  • increasing substrate conc will not affect the rate of reaction
34
Q

what is a key thing to remember with non - competitive inhibitors

A
  • increasing the substrate concentration, does not increase the reaction rate.
35
Q

what is an anabolic enzyme

A

the building up/ synthesis

36
Q

what is a catabolic enzyme

A

the breaking down/degradation

37
Q

what is the general enzyme equation

A

Enzyme + Substrate ↔ Enzyme Substrate Complex ↔ Enzyme Product Complex ↔ Enzyme + products

38
Q

what is a prosthetic group

A

tightly bound to an enzyme permanently, often contains metal ions

39
Q

what are inorganic ions

A

not permanently bound to the enzyme, may bind temporarily to either the enzyme or the substrate

40
Q

what is a coenzyme

A

they bind to the active site, for short periods of time, before or at the same time as the substance they are organic, non - protein molecules

41
Q

what are respiratory enzyme responsible for

A

the breakdown of glucose and the formation of ATP

42
Q

phosphorylases act in cytoplasm

A

phosphorylates, add phosphate groups to glucose, to keep it in the cell + make it more reactive.

43
Q

decarboxylases and dehydrogenase act in the matrix of the mitochondria

A

aerobic respiration - decarboxylases remove carbon dioxide from a molecule and dehydrogenates remove H from a molecule

44
Q

what makes ATP

A

ADP + PI -> ATP

45
Q

suggest the advantages of having an internal digestive system compared with secreting enzymes outside the organism

A
  • extracellular enzyme, secreted outside of an organism are lost to the environment
  • internal environment, can be regulated, to give optimum conditions.
46
Q

how do enzymes lower activation energy

A
  • by orientating molecules, so that reacting bonds are near to each other
  • R groups, on the enzyme may donate or accept electrons, for oxidation/ reduction reaction.
  • water, may be excluded from the reaction, due to the hydrophobic R groups in the active site, this creates more favourable conditions for the reaction
47
Q

know how to measure the rate of enzyme controlled reactions

A
48
Q

what is the calculation to work out initial rate of reaction

A

rate = change in Y/ change in X

49
Q

why is enzyme concentration, usually relatively low, in cells

A
  • enzyme can be reused
  • genes for enzymes can be switched on if required
50
Q

why must we keep pH and Temperature, constant when investing the rate of reaction, when changing the enzyme concentration

A
  • only changing the enzyme concentration
  • control Ph using a buffer
  • controlled temp, by using a thermostatically controlled water bath.
51
Q

what happens, when we increase the substrate concentration

A
  • more successful collisions between active site + substrate
  • more enzyme substrate complexes’
  • more product made per second
  • greater rate
52
Q

what is Vmax

A

the maximal reaction rate or velocity of an enzymatically catalyzed reaction when the enzyme is saturated with its substrate.

53
Q

reversible inhibitors

A
  • most competitive inhibitors do not bind permanently to the active site
  • they bind for short periods and then leave
  • removal of inhibitor from a reaction mixture, leaves enzyme molecule unaffected
54
Q

irreversible inhibitors

A
  • many non - competitive inhibitors bind permanently to enzyme molecules
  • inhibition cannot be reversed an any molecules bound by the inhibitor are inactivated.
  • inhibition is not always a bad thing, as it can help to control metabolic reactions
55
Q

what is one thing to note about inhibition

A

inhibition is not always a bad thing, as it can help to control metabolic reactions

biology a level OCR (32 decks)

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