Enzymes

Question 1

definition of enzymes

Answer 1

biological catalyst that lowers activation energy of reaction and increase rate of reaction but remains unchanged

Question 2

describe intracellular/extracellular enzymes

Answer 2

operate within cells

outside cells

Question 3

describe lock and key mechanism (4)

Answer 3

1. specific enzyme binds to substrate with specific shape
2. forms enzyme-substrate complex and reacts
3. release of products
4. enzyme reuse again

Question 4

describe induced fit mechanism

Answer 4

substrate has partially complimentary shape

enzyme changes shape slightly to hold substrate

Question 5

how are products form from enzyme substrate reaction

Answer 5

interaction of R groups and hydrolysis

Question 6

factors affecting enzyme action (4)

Answer 6

enzyme concentration
substrate concentration
temperature
pH

Question 7

describe effect of temperature on enzymes (key words) (4)

Answer 7

optimum temp.
denaturing at high tempetatures - hydrogen bonds holding precise shape is breaking
deactivating at low temperatures

Question 8

describe effect of pH on enzymes

Answer 8

lower the pH = high concentration of hydrogen ions

hydrogen ions interact with R groups - affect ionic bonding/shape

Question 9

examples of pH sensitive enzymes

Answer 9

amylase (7)

pepsin (2)

Question 10

describe competitive inhibitors

Answer 10

only works when there is higher concentration of inhibitors than substrate
has similar shape - blocks active site

Question 11

describe non competitive inhibitors

Answer 11

inhibitor binds to another part on the enzyme to alter shape = permanent

Question 12

how does the graph rate of reaction/pH look like

Answer 12

symmetrical

Question 13

describe commerical applications of enzymes (4)

Answer 13

biological washing powder
lactose free milk
crop soil fertility
brewing

Question 14

describe immobilising enzymes

Answer 14

alginate beads (enzyme lactase) which are inert
lactase breaks down lactose into galactose and b glucose

Question 15

describe advantages of immobilising enzymes (4)

Answer 15

reusable
can be stored
more tolerant of temp. changes
speedy separation

Question 16

describe disadvantages of immobilising enzymes

Answer 16

products can inhibit enzyme (feedback inhibition)

Question 17

definition of michaelis-menten constant

Answer 17

equation used to relate enzyme affinity to the rate of reaction

Question 18

definition of Vmax

Answer 18

maximum theoretical rate where all enzymes are saturated

Question 19

definition of Vo/Vi

Answer 19

initial velocity (when line is linear)

Question 20

definition of Km

Answer 20

(Vmax/2)

affinity of enzyme for a substrate

Question 21

describe graph of rate of reaction/substrate concentration

Answer 21

Vmax/2 = Km

check graph

Question 22

describe graph of enzyme inhibition (sub conc/rate of reaction)

Answer 22

competitive inhibitor:
- same Vmax
- higher Km
non competitive inhibitor:
- lower Vmax
- same Km

Question 23

describe competitive inhibitor Vmax/Km

Answer 23

Km = higher [S] needed to outcompete inhibitor
Vmax = [S] outcompetes inhibitor and has infinite supply

Question 24

describe non competitive inhibitor Vmax/Km

Answer 24

Km = enzymes left work normally
Vmax = some enzymes affected by permanent shape change

Question 25

what does an low Km mean

Answer 25

higher affinity

- enzyme only needs little substrate