Enzymes Flashcards
Why are enzymes better than chemical catalysts?
extremaly efficient, more specific (can tell difference between L and D), operate at phsyiological pH and temperature
What do some enzymes require to work?
cofactors or coenzymes
What is an apoenzyme? Holoenzyme?
enzyme that is missing something so it can’t work
has everything it needs to work
What is Vmax?
constant which is the max veloctiy enzyme can work (fixed enzyme conc)
What does k1 describe?
What order is this rate constant?
the reaction rate for how quickly E and S can combine, depends on this as well as how much S there is
2nd
What does k-1 describe?
What order is this rate constant?
the reaction rate for how quickly ES can dissociate into E and S
1st
What is the slowest step in enzymatic reaction?
k2, breakdown from ES to E + P
What is Km? What is the unit?
michealis constant, describes the relationship between substrate conc. and reaction rate
M
How can you calculate Km?
=(k-1+k2)/k1
When does Km equal substrate concentration?
when Vo is 1/2 Vmax
What is Vo?
initial velocity
What is kcat?
first-order rate constant that determines the reaction rate when the enzyme is fully occupied at a saturating concentration of the substrate
What is the specificity constant?
kcat/Km
describes real total efficiency of an enzyme (s^-1 M^-1)
What are two ways to get faster efficiency?
really big numerator or really small denominator (kcat/Km)
What is the equation of lineweaver-burk plot?
1/Vo=(Km/Vmax)(1/[S]) + 1/Vmax
Using a lineweaver-burk, Vmax is 0.02 sec/mol, x-int is -2.5mM^-1, what is Km?
0.4mM (xint equals -1/Km so (-1/-2.5)
What does x-int of lineweaver-burk plot equal?
-1/Km
What factors affect enzyme activity?
substrate concentration, temperature, pH
What are some features of the active sites of enzymes?
shape mimics substrate, small compared to rest of enzyme, substarets are held in by waek covalnet bonds
What are the types of enzyme inhibition?
competitive, uncompetitive, mixed competitive
What is competitive inhibtion? What does it impact?
competes for active site with substrate
changes the Km
How does competitive inhibition change michaelis-menton equation?
a is added to equation
Vo=Vmax[S]/(aKm+[S])
where a=1+[I]/Ki and Ki=[E][I]/[EI]
How does competitive inhibition change lineweaver-burk plot?
change the slope and x-intercept
What is uncompetitive inhibtion? What does it impact?
binds away from active site and strains enzyme
reduces efficinecy
