Cell biochemistry Flashcards
What is an exergonic reaction?
Spontaneous reaction because delta G is negative
What is an endergonic reaction?
lower energy to higher energy reaction so not favourable
An enzyme can be used to lower the activation energy
What is kcat?
The turnover number for an enzyme
What are the assumptions of the M-M scheme?
- assume that the reverse reaction of negligible
- assume only a single central complex exists
- assume [S]»_space; [E]
What is the equation for Vmax and what is it?
Vmax = kcat[E]t
It is the maximum specific activity of the enzyme
What is vo?
Half of Vmax
What is Km?
The substrate concentration where the reaction rate is half the maximal
A low Km indicates the enzyme only requires a small amount of substrate to become saturated
How can enzyme efficiency be measured?
Kcat/Km
What do the intercepts on the Lineweaver-Burk plot show?
y-intercept - 1/Vmax
x-intercept - -1/Km
What is on the axes of a Lineweaver-Burk plot?
x axis - 1/[S]
y axis - 1/vo
What are limitations of the Lineweaver-Burk plot?
It is highly sensitive to measurements at low [S]
The line of best fit is highly influenced by the last point
Competitive inhibitors
Bind to active site
Km increases
Vmax unaltered
Draw graph
Non-competitive inhibitors
Inhibitor binds to allosteric site
Km unaltered
Vmax reduced
Draw graph
What assays can be used to measure protein concentration and how do they work?
Bradford
BCA
Measures colour change
What is the plank-einstein relationship?
E = hc/lamda E is the energy carried by the electromagnetic radiation h is the plank constant c is the speed of light lamda is wavelength
