2.4 enzymes

Question 1

enzyme type of protein

Answer 1

globular

Question 2

intracellular enzyme example

Answer 2

catalase
hydrogen peroxide -> hydrogen + water

Question 3

extracellular enzyme example

Answer 3

amylase (starch-> maltose)
trypsin (protein -> amino acids)

Question 4

active site

Answer 4

• part of enzyme that the substrate binds to
• COMPLEMENTARY and SPECIFIC shape

Question 5

lock and key model

Answer 5

• enzyme = lock, substrate -= key
• specific shape (enzyme only catalyses ONE type of reaction)

Question 6

how do enzymes catalyse reaction

Answer 6

alternative pathway with a lower activation energy

Question 7

induced fit hyporthesis

Answer 7

• AS of enzyme not perfectly completmentary
• substrate moves into active site, interacts with active site, interferes with bonds and changes the shape of active site so its a perfect fit
• affects bonds in substrate (easier to make or break)

Question 8

4 steps of enzyme reaction

Answer 8

1. enzyme and substrate (separate)
2. enzyme substrate complex
3. enzyme product complex
4. enzyme and product (separate)

Question 9

pH on enzyme

Answer 9

• denatures at extremes
• optimum differs for every enzyme
• high conc of H+ ions
• disrupt interactions between r groups (ionic bonds/H bonds)
• change tertiary structure
• substrate no longer can bind to active site
• enzymedenatured

Question 10

denaturing

Answer 10

• tetriary structure altered
• shape of active site changed
• AS no longer complementary to subtrate
• S cannot bind to form ESC
• rate slows

Question 11

typical optimum temperature in animals

Answer 11

37 degrees

Question 12

effect of temp on enzymes

Answer 12

• low temp enzymes are inactive, KE too low, infrequent collisions so few ESC formed
• as temp increases, KE increases, move more quickly, more ES collisions so more ESC formed
• temp too high, R group interactions in tertiary structure broken, shape changes, denatured

Question 13

enzyme and substrate conc

Answer 13

• as conc increases, rate increases up until v max
• more frequent successful collisions between ACTIVE SITE and substrate
• more ESC’s formed
• plateau at v max (max rate)
• active site saturation
• substrate conc no longer limiting reagent- enzyme concentration is limiting

Question 14

PRACTICAL CONSIDERATIONS (6)

Answer 14

• vol and conc of enzyme
• vol and conc of substrate
• temperature control (thermostatic water bath)
• pH control (buffer solution)
• repeat and mean (reliability)
• range bars

Question 15

coenzymes

Answer 15

• organic
• take part in reaction and are changed
• then recycled for other reactions- carry chemicals between enzymes

Question 16

cofactors

Answer 16

non protein substance required by an enzyme in order to function

Question 17

prosthetic group

Answer 17

• PERMANENT cofactor
• contributes to final 3d shape
  eg Zn2+ in carbonic anhydrase

Question 18

coenzyme example

Answer 18

vitamins

Question 19

prosthetic group example

Answer 19

zinc in carbonic anhydrase

Question 20

inroganic ion cofactor + example

Answer 20

• combine w enzyme or sustrate to allow ESC to form more easily
• amylase and cl- ions

Question 21

competitive inhibitors explain

Answer 21

• shape similar to substrate, complementary to active site
• bind to active site, TEMPORARILY preventing substrate from entering
• fewer active sites available for substrate
• eventaully, substrate out competes inhibitor so rate reaches normal as more ESC formed

Question 22

non-competitivie inhibitors

Answer 22

• fit into allosteric site
• cause a confrimational change in the shape of the enzyme
• affects active site, no longer complementary so substrate cant bind

Question 22

non-reversible inhibitors

Answer 22

bind permanently to enzyme

Question 22

product inhibition

Answer 22

• product inhibits the enzyme
• prevents too much product from being made

Question 23

reversible inhibitors

Answer 23

occupy ennzyme briefly

Question 24

Q10

Answer 24

• for every 10 degree increase, how much rate is affected
• CALCULATE: rate at t+10/rate at t

Question 25

effects of altering low temp vs high temp

Answer 25

low = REVERSIBLE
high = IRREVERSIBLE

Question 26

experiment for cofactor action

Answer 26

• reaction without cofactor
• with 3 diff concs of cofactor
• control [enzyme], [substrate], optimum temp and pH
• repeat and mean

Question 27

why do scientist accept induced fit over lock and key

Answer 27

more evidence to support

Question 28

evidence from graph of competitive

Answer 28

• at high substrate conc
• rate approaches rate WITHOUT inhibitor, as increased substrate conc overcomes inhibition

Question 29

how can you tell its a competitive inhibitor(visually)

Answer 29

1. substrate and inhibitor similar shape
2. specific shape complementary to active site, able to bind
3. reference the same bond if shown