Enzymes Flashcards
definition of enzymes
biological catalyst that lowers activation energy of reaction and increase rate of reaction but remains unchanged
describe intracellular/extracellular enzymes
operate within cells
outside cells
describe lock and key mechanism (4)
- specific enzyme binds to substrate with specific shape
- forms enzyme-substrate complex and reacts
- release of products
- enzyme reuse again
describe induced fit mechanism
substrate has partially complimentary shape
enzyme changes shape slightly to hold substrate
how are products form from enzyme substrate reaction
interaction of R groups and hydrolysis
factors affecting enzyme action (4)
enzyme concentration
substrate concentration
temperature
pH
describe effect of temperature on enzymes (key words) (4)
optimum temp.
denaturing at high tempetatures - hydrogen bonds holding precise shape is breaking
deactivating at low temperatures
describe effect of pH on enzymes
lower the pH = high concentration of hydrogen ions
hydrogen ions interact with R groups - affect ionic bonding/shape
examples of pH sensitive enzymes
amylase (7)
pepsin (2)
describe competitive inhibitors
only works when there is higher concentration of inhibitors than substrate
has similar shape - blocks active site
describe non competitive inhibitors
inhibitor binds to another part on the enzyme to alter shape = permanent
how does the graph rate of reaction/pH look like
symmetrical
describe commerical applications of enzymes (4)
biological washing powder
lactose free milk
crop soil fertility
brewing
describe immobilising enzymes
alginate beads (enzyme lactase) which are inert lactase breaks down lactose into galactose and b glucose
describe advantages of immobilising enzymes (4)
reusable
can be stored
more tolerant of temp. changes
speedy separation
describe disadvantages of immobilising enzymes
products can inhibit enzyme (feedback inhibition)
definition of michaelis-menten constant
equation used to relate enzyme affinity to the rate of reaction
definition of Vmax
maximum theoretical rate where all enzymes are saturated
definition of Vo/Vi
initial velocity (when line is linear)
definition of Km
(Vmax/2)
affinity of enzyme for a substrate
describe graph of rate of reaction/substrate concentration
Vmax/2 = Km
check graph
describe graph of enzyme inhibition (sub conc/rate of reaction)
competitive inhibitor: - same Vmax - higher Km non competitive inhibitor: - lower Vmax - same Km
describe competitive inhibitor Vmax/Km
Km = higher [S] needed to outcompete inhibitor Vmax = [S] outcompetes inhibitor and has infinite supply
describe non competitive inhibitor Vmax/Km
Km = enzymes left work normally Vmax = some enzymes affected by permanent shape change
what does an low Km mean
higher affinity
- enzyme only needs little substrate