enzymes + enzyme kinetics Flashcards
features of enzymes
- 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
2 groups that can alter enzyme activity
- co factors + co enzymes
co factors + examples
- inorganic compounds joined to enzyme
- coordination complex (metalloprotein)
e. g. Fe, Zn, Pb, Cu
co enzymes + examples
- organic molecules bonded to enzyme
e. g. CoA, NAD, FAD, haem
features of co enzymes
- only transiently (temporarily) bind to enzyme
- Undergo conformational change during the reaction
- Resume normal conformation at end of reaction
prosthetic group
- cofactor/ coenzyme covalently bonded to enzyme
enzyme without a cofactor/ coenzyme
- apoenzyme
enzyme with a cofactor/ coenzyme
- holoenzyme
2 mechanism of enzyme substrate binding
- lock and key
- induced fit
isozymes
- enzymes that catalase the same reaction but have different physical properties
- can be used to determine physiological events within the body (diagnostic tool)
zymogen
- inactive precursor to a enzyme
enzyme kinetic graph axis
Y= rate of reaction (V) x= substrate conc. (S)
V max
maximum rate reached by enzyme
- hard to see on hyperbola as Vmax reached at infinite enzyme conc.
Km
- concentration of substrate required for enzyme to be at 50% Vmax
- illustrates enzymes efficiency
Michaelis Menton equation for Km
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
what is V0
intial rate of reaction at a given conc.
calculation giving straight line
1/V0= (Km/Vmax)(1/S) + 1/Vmax
V max from straight line =
y intercept = 1/Vmax
Km from staright line
x intercept = -1/Km
low Km
- enzyme is efficient
low conc. of substrate needed
high Km
- enzyme is inefficient
high conc. needed to convert to products
enzymes can have same v max and different Km
true
environmental inhibitors on enzymes
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
two types of inhibitors
reversible and irreversible
2 types of reversible + 1 type of irreversible
reversible: - competitive - non competitive irreversible - non competitive
features of irreversible non competitive inhibitors
- bind to allosteric site, degrade the enzyme
features of reversible competitive inhibitors
- fight for space on active site
- effect negated by increasing substrate conc.
- Km varies but Vmax = constant
features of reversible non competitive inhibitors
binds to allosteric site, changes conformation of enzyme
- Km remains constant
- Vmax varies
features of feedback inhibition
- product of a reaction acts as a non competitive inhibitor - binding to enzymes allosteric site
