2.4 enzymes Flashcards
(35 cards)
1
Q
enzyme type of protein
A
globular
2
Q
intracellular enzyme example
A
catalase
hydrogen peroxide -> hydrogen + water
3
Q
extracellular enzyme example
A
amylase (starch-> maltose)
trypsin (protein -> amino acids)
4
Q
active site
A
- part of enzyme that the substrate binds to
- COMPLEMENTARY and SPECIFIC shape
5
Q
lock and key model
A
- enzyme = lock, substrate -= key
- specific shape (enzyme only catalyses ONE type of reaction)
6
Q
how do enzymes catalyse reaction
A
alternative pathway with a lower activation energy
7
Q
induced fit hyporthesis
A
- 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)
8
Q
4 steps of enzyme reaction
A
- enzyme and substrate (separate)
- enzyme substrate complex
- enzyme product complex
- enzyme and product (separate)
9
Q
pH on enzyme
A
- 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
10
Q
denaturing
A
- tetriary structure altered
- shape of active site changed
- AS no longer complementary to subtrate
- S cannot bind to form ESC
- rate slows
11
Q
typical optimum temperature in animals
A
37 degrees
12
Q
effect of temp on enzymes
A
- 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
13
Q
enzyme and substrate conc
A
- 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
14
Q
PRACTICAL CONSIDERATIONS (6)
A
- 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
15
Q
coenzymes
A
- organic
- take part in reaction and are changed
- then recycled for other reactions- carry chemicals between enzymes
16
Q
cofactors
A
non protein substance required by an enzyme in order to function
17
Q
prosthetic group
A
- PERMANENT cofactor
- contributes to final 3d shape
eg Zn2+ in carbonic anhydrase
18
Q
source of coenzymes
A
derived from vitamins
19
Q
prosthetic group example
A
zinc in carbonic anhydrase
20
Q
inroganic ion cofactor + example
A
- combine w enzyme or sustrate to allow ESC to form more easily
- amylase and cl- ions
21
Q
competitive inhibitors explain
A
- 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
22
Q
non-competitivie inhibitors
A
- fit into allosteric site
- cause a confrimational change in the shape of the enzyme
- affects active site, no longer complementary so substrate cant bind
22
Q
non-reversible inhibitors
A
bind permanently to enzyme
22
Q
product inhibition
A
- product inhibits the enzyme
- prevents too much product from being made: negative feedback???
23
reversible inhibitors
occupy ennzyme briefly
24
Q10
- for every 10 degree increase, how much rate is affected
- CALCULATE: rate at t+10/rate at t
25
effects of altering low temp vs high temp
low = REVERSIBLE
high = IRREVERSIBLE
26
experiment for cofactor action
- reaction without cofactor
- with 3 diff concs of cofactor
- control [enzyme], [substrate], optimum temp and pH
- repeat and mean
27
why do scientist accept induced fit over lock and key
more evidence to support
28
evidence from graph of competitive
- at high substrate conc
- rate approaches rate WITHOUT inhibitor, as increased substrate conc overcomes inhibition
29
how can you tell its a competitive inhibitor(visually)
1. substrate and inhibitor similar shape
2. specific shape complementary to active site, able to bind
3. reference the same bond if shown
30
cofactors vs coenzyme
- coenzyme is organic
- directly participate in reaction
31
inTRAcellular enzyme eg
catalase
32
extracellular enzyme eg
amylase
33
cl-
- cofactor
- for amylase
