enzymes + enzyme kinetics

Question 1

features of enzymes

Answer 1

• biological catalysts
• made of proteins
• speed up rate of reaction
  Position of equilibrium un altered
• stabilise transition state, lowers activation energy
  -specific to substrate
• work most effectively under normal physiological parameters

Question 2

2 groups that can alter enzyme activity

Answer 2

• co factors + co enzymes

Question 3

co factors + examples

Answer 3

• inorganic compounds joined to enzyme
• coordination complex (metalloprotein)
  e. g. Fe, Zn, Pb, Cu

Question 4

co enzymes + examples

Answer 4

• organic molecules bonded to enzyme

e. g. CoA, NAD, FAD, haem

Question 5

features of co enzymes

Answer 5

• only transiently (temporarily) bind to enzyme
• Undergo conformational change during the reaction
• Resume normal conformation at end of reaction

Question 6

prosthetic group

Answer 6

• cofactor/ coenzyme covalently bonded to enzyme

Question 7

enzyme without a cofactor/ coenzyme

Answer 7

• apoenzyme

Question 8

enzyme with a cofactor/ coenzyme

Answer 8

• holoenzyme

Question 9

2 mechanism of enzyme substrate binding

Answer 9

• lock and key

- induced fit

Question 10

isozymes

Answer 10

• enzymes that catalase the same reaction but have different physical properties
• can be used to determine physiological events within the body (diagnostic tool)

Question 11

zymogen

Answer 11

• inactive precursor to a enzyme

Question 12

enzyme kinetic graph axis

Answer 12

Y= rate of reaction (V)
x= substrate conc. (S)

Question 13

V max

Answer 13

maximum rate reached by enzyme

- hard to see on hyperbola as Vmax reached at infinite enzyme conc.

Question 14

Km

Answer 14

• concentration of substrate required for enzyme to be at 50% Vmax
• illustrates enzymes efficiency

Question 15

Michaelis Menton equation for Km

Answer 15

Km= k-1 + k2/ k1 
K1= rate of forward reaction (to transition stage)
K-1 = reverse rate of reaction (transition stage)
k2 = rate of reaction from transition to product

Question 16

what is V0

Answer 16

intial rate of reaction at a given conc.

Question 17

calculation giving straight line

Answer 17

1/V0= (Km/Vmax)(1/S) + 1/Vmax

Question 18

V max from straight line =

Answer 18

y intercept = 1/Vmax

Question 19

Km from staright line

Answer 19

x intercept = -1/Km

Question 20

low Km

Answer 20

• enzyme is efficient

low conc. of substrate needed

Question 21

high Km

Answer 21

• enzyme is inefficient

high conc. needed to convert to products

Question 22

enzymes can have same v max and different Km

Answer 22

true

Question 23

environmental inhibitors on enzymes

Answer 23

temperature
-too hot denatures enzyme, looses conformation
- too cold not enough substrate has activation energy
pH
- changes cause change in charge of groups
- causes conformational change
detergents
- e.g. urea disrupt hydrophobic interactions
Reducing agents
- break disulfide bonds - conformational change

Question 24

two types of inhibitors

Answer 24

reversible and irreversible

Question 25

2 types of reversible + 1 type of irreversible

Answer 25

reversible:
- competitive 
- non competitive 
irreversible 
- non competitive

Question 26

features of irreversible non competitive inhibitors

Answer 26

• bind to allosteric site, degrade the enzyme

Question 27

features of reversible competitive inhibitors

Answer 27

• fight for space on active site
• effect negated by increasing substrate conc.
• Km varies but Vmax = constant

Question 28

features of reversible non competitive inhibitors

Answer 28

binds to allosteric site, changes conformation of enzyme

• Km remains constant
• Vmax varies

Question 29

features of feedback inhibition

Answer 29

• product of a reaction acts as a non competitive inhibitor - binding to enzymes allosteric site