Enzyme catalysis Flashcards
what are enzymes usually made of
proteins, sometimes RNA
enzymes are biological catalysts…
ctalyse reactions under biologically relevant conditoins - about 37*C, neutral pH (except stomach, lysozymes…) and 10^-6 to 10^-3M
can the active site have prosthetic groups
yes
how do enzymes work
A+B A.B [transition state] C.D C+D
describe transition state
between reactants and products. highest energy!
describe induced fit model
active site changes shape to accomodate for substrate. Then, it changes shape to help form the transition state, lowering the transition state’s energy, hence lowering the energy of the reaction
describe dfiference in energy profile diagrams for catalysed vs uncatalysed
uncatalysed has 3 bumps, top of middle one represents transition state, bottom of middle one represents A.B and C.D
How do we get Michaelis Menten Curve
First, we plot product concentration against time for various concentrations of a product.
We calculate the initial velocity
Then we plot initial velocity against substrate concentration.
describe Vmax
Varies with temperature and concentration: doubled conc = doubled V max.
Ms-1
describe Km
conc @ 1/2 Vmax
independent of concentration
M
increased Km = decreased enzyme affinity.
michaelis menten curve equation?
Vmax[s]/(Km + [s])
what are the axes and intercepts for Lineweaver Burk plot?
y axis: 1/[Vo]
x axis: 1/[S]
Y int: 1/Vmax
X int: -1/Km
what is irreversible inhibition
substrate binds covalently to active site. Inhibits enzyme permanently
what is reversible inhibition
substrate binds non covalently to enzyme, not necessarily at the active site.
3 types of reversible inhibition?
competitive inhibition
uncompepitivie inhibition
mixed/non competitive inhibition
describe competitive inhibition
inhibitor binds non covalently to active site.
V max unchanged.
Km increases
describe non competitive inhibition
inhibitor binds non covalently to ENZYME SUBSTRATE COMPLEX
Forms parallel lines.
As [I] Increases, 1/Vmax increasses (therefore Vmax decreases)
As [I] increases, -1/Km increases in magnitude (wherefore m decreases)
describe mixed inhibition
inhibitor binds non covalently to enzyme substrate complex or to the enzyme on its own (not the active site though).
Vmax decreases
Km can increase or decrease.
what are isozymes
enzymes that catalyse the same reaction but have different primary structures.
Often occur in different tissues, and produced by different genes
describe allosteric enzymes
binding of a modulator to the enzyme changes its shape and functionality. therefore, its kinetics differ from michaelus menten model.
