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Question 1

what are enzymes? and how do they work?

Answer 1

biological catalysts. speed up reactions but don’t get used up. offer an alternate pathway with a lower activation energy

Question 2

what biological reactions are enzymes involved in?

Answer 2

metabolism= anabolic and catabolic

Question 3

what are anabolic reactions?

Answer 3

synthesis

Question 4

what are catabolic reactions?

Answer 4

breakdown

Question 5

what type of proteins are enzymes?

Answer 5

globular

Question 6

what forms the active site?

Answer 6

9-12 amino acids

Question 7

how do substrates and active sites fit?

Answer 7

each type of enzyme is specific to one substrate as each active site shape is complementary to the shape of the substrate

Question 8

how are there different active sites?

Answer 8

different sequencing of amino acids and bonds between r groups in tertiary structure

Question 9

what are the two models of enzyme action?

Answer 9

lock and key hypothesis, induced fit

Question 10

what is lock and key hypothesis?

Answer 10

enzyme and substrate are exact fits. enzyme + substrate = enzyme-substrate complex (when bound changes occur to bonds in substrate) = products (enzyme is unchanged, products are different shape so don’t stay bound to active site)

Question 11

what is the induced fit hypothesis?

Answer 11

the shapes of the active site and substrate change slightly to allow enzyme-substrate complexes to form (e.g in lysozyme)

Question 12

what are the types of enzymes?

Answer 12

intracellular and extracellular

Question 13

what are intracellular enzymes?

Answer 13

produced and catalyse reactions within a cell (e.g for the stages of respiration that occur in the cytoplasm)

Question 14

what are extracellular enzymes?

Answer 14

secreted out of cells, catalyse reactions outside of cells (e.g digestive enzymes)

Question 15

explain the practical of breakdown of starch by amylase.

Answer 15

tube 1= 8ml 1% starch, tube 2= 1ml pH 7 buffer and 1ml 1% amylase (leave 3 mins for buffer to affect the enzyme). spitting tile = 3 drops iodine in each well. add enzyme to starch and gently shake. take a sample at 0 mins then every min

Question 16

what conclusion can be taken from the breakdown of starch by amylase?

Answer 16

the longer the amylase is in the starch the lighter the iodine becomes which means there is less starch present

Question 17

what are the factors that affect enzymes?

Answer 17

temperature, pH, substrate concentration, enzyme concentration

Question 18

how does temperature affect enzymes?

Answer 18

as temperature increases the rate increases (at higher temps enzymes and substrate molecules have greater kinetic energy, increased frequency of successful collisions to form enzyme-substrate complexes)

Question 19

what is the optimum temp for humans?

Answer 19

37

Question 20

what happens to enzymes at higher temperatures?

Answer 20

enzymes denature

Question 21

how do enzymes denature?

Answer 21

as temperature increases, atom vibration increases, this leads to the breaking of bonds (e.g hydrogen bonds) in the tertiary structure, the active site changes shape and is no longer complementary to the shape of the substrate, decrease in enzyme-substrate complexes so decrease in rate

Question 22

how does pH affect enzyme activity?

Answer 22

enzymes function over a narrow range of pHs, small deviations from optimum bring about reversible changes, large deviations cause the enzyme to denature, this is due to the effect of H+ or OH- ions on bonds in the tertiary structure, decrease in enzyme-substrate complexes = decrease in rate

Question 23

how does low substrate concentration affect enzyme activity?

Answer 23

at low substrate concentrations the enzymes only have a few substrate molecules to react with so active sites aren’t working to full capacity, therefore controlling the reaction.

Question 24

how does high substrate concentration affect enzyme activity?

Answer 24

at high substrate concentrations (critical concentrations) all active sites are occupied so rate is at maximum, when all enzymes active sites are full it is known as being saturated

Question 25

how does enzyme concentration affect enzyme activity?

Answer 25

increase in enzymes means there is more active sites available so rate increases

Question 26

what is turn-over time?

Answer 26

number of substrate molecules an enzyme can turn over in a period of time

Question 27

what does it mean that enzymes are reused?

Answer 27

only a low concentration needed to catalyse a number of reactions

Question 28

how should temperature, pH, substrate conc and enzyme conc be controlled?

Answer 28

temp= water bath, pH= pH buffer solution, substrate + enzymes = same conc and volume (measuring cylinder)

Question 29

what is the control experiment for enzymes?

Answer 29

boiled then cooled enzyme (denature it) with sake conditions/ conc to show there’s no other factors that affect rate

Question 30

what are inhibitors?

Answer 30

slow/stop enzyme catalysed reactions

Question 31

what are the two types of inhibitors?

Answer 31

competitive and non-competitive

Question 32

how do competitive inhibitors work?

Answer 32

I and S are similar shapes, I can fit into E’s active site which prevents S from binding, this reduces the frequency of collisions to form E-S complexes, rate decreases

Question 33

how does conc of substrate affect inhibitors?

Answer 33

at low substrate conc I decreases rate but at high substrate conc there rate is not affected. this is because there are so many S molecules that they are more likely to collide with the active site than the I

Question 34

how do non-competitive inhibitors work?

Answer 34

S and I are different shapes, I can’t bind to the active sit but binds to allosteric site, disrupts bonding in active site so it changes shape, E and S are no longer complementary, fewer E-S form, rate decreases

Question 35

how does substrate concentration affect non-competitive inhibitors?

Answer 35

even at high S concentrations the rate is reduced, this is because ! doesn’t bind to active site so the active sites shape could have been changed already

Question 36

what are ‘free’ enzymes?

Answer 36

able to move

Question 37

what are immobilised enzymes?

Answer 37

are not able to move

Question 38

what are immobilised enzymes attached to?

Answer 38

inert support (unreactive)

Question 39

what are the two methods of immobilised enzymes?

Answer 39

entrapment in sodium alganate beads, cross linking to attach to a cellulose pad

Question 40

what is clinistix?

Answer 40

used to test the conc of glucose in urine (symptom of diabetes)

Question 41

what are biosensors?

Answer 41

used by diabetics to test blood glucose, also used to detect chemicals (e.g pollutants)

Question 42

what are the advantages of immobilised enzymes?

Answer 42

enzyme can be kept separate / removed from the product, easy to reuse (decreases cost of industrial process), product is not ‘contaminated’ with enzyme (good because some people can be allergic to an enzyme), they are more stable so this method provides a barrier against these changes, enzymes work over wider range of pH, enzymes denature at higher temps (so can use higher temp=faster rate)

Question 43

what are the disadvantages of immobilised enzymes?

Answer 43

initial cost and time needed for immobilisation, initial and maximum rate of reaction may be lower (harder to form E-S complexes)