Enzymes Flashcards
Why are immobilized enzymes less effected by ph+ temp
- mols held firmly in shape by alginate
- not fully exposed to temp OR pH
Induced fit hypothesis
- substrate is partially complimentary to active site
- AS changes shape slightly to ensure better fir + stronger binding of substrate
- ESC forms
- Ea is lower
Non competitive inhibition
- Mol fits into allosteric site of enzyme rather than AS
- Disrupts 3d shape of enzyme/change in tertiary structure
- Change in shape of AS
- Reduces RO enzyme activity as prevents subst fitting into AS —> unable to form ESC
- Vmax decreases/not reached —> ROR decreases as reaction progresses = conc of effective enzyme decreases
- KM STAYS THE SAME - Non reversible as increasing subst conc HAS NO EFFECT
Suggest how molecular structure of enzyme changes during ‘cold denaturation’
- AS has specific shape
- complementary to substrate
- some enzymes induced fit mechanism
- formation of ESC
- lowering Ea = substrates held closer together for bond formation + places strain on bonds to break
Induced fit model
- Collisions between enzyme + substrate e occur as subst nears AS
- AS undergoes conformational change/changes shape to ensure better fit + stronger binding = complementary to substrates and active site.
- Changed shape of AS puts strain on bonds of substrate = ESC as disruption in bonds of substrate
- Product formed leaves enzyme + enzymes AS returns to original shape/ reversible
- Catalysis more efficient
INDUCED FIT vs LOCK N KEY
INDUCED
- shape of subst not fully complementary to shape of AS
- AS flexible around substrate
- Provides better fit/fully complemtry
LOCK N KEY
- Shape of subst complemntry to shape of AS
- AS shape doesn’t change
- Substrate fits into AS
What’s true for a modified enzyme + what would happen if pH is altered in 3d shape
- Higher affinity for substrate
- H+ ions attach themselves to negatively charged R groups
What factors affect rate of enzyme catalysed reaction in the presence of non competitive inhibitor
- enzyme conc
- inhibitor conc
- substrate conc
Michaelis menttoncconstant (km)
- Substrate conc @ when enzyme works at 1/2 of max rate
- half of as of enzyme occupied by substrate
- Km is affinity of enzyme for substrate
- High affinity = low km value
- Low affinity= High Km value
Structure of enzyme
- Globular protein (spherical shape) that catalyses metabolic reactions
- Function as biological catalysts
- Specific in nature
- Precise 3D shape w hydrophilic R groups on outside
- Soluable
SUBSTRATE CONC
- Increasing subst conc = initial ROR increases
- More subst available = increased chance of collision + binding w enzymes AS
- After certain point (saturation point) = ROR plateaus regardless of further increase in subst levels —> ENZYME WORKING AT VMax
- All active sites bound/filled
- Enviornment is saturated w substrates + enzymes bound @ VMax
- Enzyme moves to fuel substrate = less collisions + ROR decreases
Enzyme catalysis
1, Mol will move randomly around constantly = IN AQEOUS CONDITION
2. ENzyme catalysis requires subst to be brought in close proximity w AS
3. Complex mol = smaller mol bound tgt
4. E catalyses the conversion of subst —> ESC
5. E + product dissociate = E not consumed
COMPETITIVE INHIBITION
- Compete w subst for AS
- Mol w similar shape to enzymes subst binds w/ AS inhibiting function
- Affinity for subt to enzyme decreases = HIGH KM value
- change in tertiary SS of enzyme = decreases enzyme activity - If conc of inhibitor rises= subst falls —> less likely subst collide w enzyme AS
- Can be reversed by increasing conc of substrate = fewer comp inhib binding to enzyme
VMax definition + higher the VMax…?
- theoretical max ROR
- More efficient E+S
- lower km
- Faster reaction
- Faster to reach Vmax
Disadvantages of immobilizing enzymes
- cost of development = high
- E can be detached from solid support
- shape of E changed
Lock + Key hypothesis
- Enzymes AS complemtry to substrate e precisely/specific to substrate
- Subst fits a particular AS like a key fits into complemntry/particular lock
Adv of immobilizing enzymes
- Enzyme is reused
- Enzyme easily recovered
- Product contaminated w enzymes
- Reduces product inhibition
- E more stable/less likely to denature
- Longer shelf life of enzyme
How do enzymes reduce Ea
- SUbst not converted to product UNLESS temporarily given energy
- Extra energy in Ea
- E hold S in way that bonds easily broken = reducing Ea
- Enzyme binding to S + destabilizes bonds in a subst
- Shape slightly changed = easier to fit substrate to product
How does pH effect ROR
- Alters charge of E = effects hydrophilic r groups of AA —> effects ionic bonding
- Disrupts secondary/tertiary ss
- Ph= measure of H+ in solution
- AS changed/denatured (acid is proton donor)
- Changes protein solubility
- AS diminishes ability to bind to S
TEMP + ENYZMES
- Increasing temp = increase speed + motion of E and S —> high E activity
- Higher KE= more frequent + stronger collisions between E+ S
- At optimum = rate of enzyme activity PEAKS
- Temp past optimum = enzyme stability decreases = more thermal energy + disrupts H+ bonds
- Causes enzymes AS to lose shape/denaturation
- At low temp = insufficient thermal energy for EA/activation of enzyme = catalysed reaction to proceed
Why can enzyme convert subst mol so quickly
- Mol within cells move around quickly via diffusion of short distances w 10K of collisions per min
- Occuring between S + E
What could be the value of Km with inhibitor compared to the value of Km with no inhibitor?
competitive inhibitor: more
non-competitive inhibitor: less
Protein to AA End product inhibition
- Protein binds to trypsin AS = peptides
- Peptides bind to AS of Peptidase = AA
- AA bind to AlLOSTERIC SITE of trypsin= conformational change of AS/chaneg in tertiary ss
- to prevent excess production
*** Non comp inhibition
describe method allowing use of immobolized amaylse to collect product only containing reducing sugar
- close bottom tap for hydrolysis to occur
- run starch solution through column to collect product REPEEAT
- use more enzymes in beads
- use longer narrower column
- test product w/ iodine in potassium iodide solution
- if blue black from orange = starch present
describe how bacteria can be immobolised in beads of alginate
- bacteria placed in sodium alginate
- place mixture in syringe
- add drops of mixture to calcium chloride solution
- calcium ions replace sodium ions = beads
- bacteria trapped in beads
