behaviour of proteins Flashcards
biological catalyst, usually globular proteins
enzymes
what is the factor that increase the rate of the enzyme reaction
10^20 over an uncatalyzed reaction
it is the difference between energies of reactants and products under standard condition
standard free energy, ΔG°
true or false:
enzymes can speed up reactions and can alter the equilibrium constant or the free energy change
false - cannot alter
it is the energy input required to initiate a reaction
activation energy, ΔG°‡
- reaction rate depends on it
what is the relationship between the temperature of a mixture and the energy available to the reactants to reach the transition state
as the temp increase, the energy increase
Description of a reaction whose rate depends on the first power of the concentration of a single reactant
first order
Description of a reaction whose rate depends on the product of the concentrations of two reactants
second order
Portion of the enzyme surface to which the substrate binds via noncovalent forces (examples) and at which the reaction takes place
active site
(hydrogen bonding
electrostatic attractions - glutamic acid and aspartic acid
van der Waals attractions - if non polar)
it is a reactant
substrate
substrate binds to that portion of the enzyme with a complementary shape
lock and key model
Binding of the substrate induces a change in the conformation of the enzyme that results in a complementary fit
induce fit model
what is the difference between lock-and-key model and induce fit model
lock-and-key model: no room for flexibility
induce fit model: have room for flexibility
similarities: both gives off product
it has a different three-dimensional shape before the substrate is bound
binding site
energy when ES complex bound together
lower on energy than at the start
inverse measure of the affinity of the enzyme for the substrate
Km, Michaelis constant
Substrate binds to the enzyme and releases a product before the second substrate binds to the enzyme
Ping-pong mechanism
Substrates can bind to the enzyme in any order
Random mechanism
mM
millimoles per liter
1 mM = 1×10–3 mol L–1
Substrates have to bind to the enzyme in a specific order
Ordered mechanism
Number of moles of substrate that react to form product per mole of enzyme per second
turnover number
kcat or kp
true or false:
increase turnover no, increase enzyme activity
True
as turnover no. is the rate on how fast are the changes from the enzyme> substrate > product
examples of enzyme-catalyzed reactions and its curve
Chymotrypsin - hyperbolic, negative cooperativity
Aspartate -transcarbamoylase (ATCase) - sigmoidal, positive cooperativity
Substances that decrease the rate of an enzymecatalyzed reaction
inhibitors
Reversible inhibitors vs Irreversible inhibitors
Reversible inhibitors:
substances that bind to an enzyme and subsequently released
- competitive:
compete the AS
Vmax: unchanged
Km: increased
* it can overcome by high substrate concentration - noncompetitive:
bind to enzyme other than AS
Vmax:
pure - decreased
mixed - decreased
Km:
pure - unchanged
mixed - decreased
* lineweaver-burk plot contains parallel lines - Vmax and Km decreases - uncompetitive inhibitors:
not to the actual enzyme
Vmax and Km decreases
Irreversible inhibitors:
forms covalent bond to part of AS
permanently preventing substrates from occupying it
common table sugar
Sucrose - made of glucose and fructose
Similar to noncompetitive inhibition but the binding of I does affect the binding of S and vice versa
Mixed Noncompetitive Inhibition
*means everything changes, ur Vmax and Km
Molecules used to bind to an enzyme irreversibly and inactivate it
suicide substrate
