Enzymes Flashcards
what does rate depend on?
rate depends on the frequency of successful collisions between the substrate and the active site
what is the effect of temperature on enzyme controlled reactions?
as we increase temperature, rate of reaction increases
this is because we are increasing the kinetic energy of the enzyme and the substrate
because they are moving more rapidly the chance of more successful collisions increases
at a certain temperature the reaction is at its maximum (optimum temperature)
as the temperature increases past it’s optimum, the rate of reaction decreases
this is because at higher temperatures the enzyme molecules are vibrating more rapidly, and this vibrations cause bonds within the enzyme to break such as hydrogen and ionic bonds
because of this the tertiary structure of the enzyme molecules begins to change
as the shape of the active site changes, it no longer becomes complimentary to the substrate (denatured)
what is the optimum temperature for human enzymes typically ?
40°c
what is the effect of substrate concentration in enzyme controlled reactions ?
for a given enzyme concentration, increasing the substrate concentration will increase the rate of the reaction to a particular point at which the rate is at its maximum (Vmax)
1) the rate of reaction initially increases as number of successful collisions between enzyme and substrate increases
2) the rate of reaction then levels out when all enzyme molecules are taken up by substrate molecules (enzyme-substrate complex)
3) the active sites are saturated
4) at this point rate of reaction is limited by concentration of enzyme
what is the structure of competitive inhibitor ?
a similar structure to the normal substrate molecule and competes with it for the attachment to the active site
how is the rate of reaction reduced with competitive inhibitors?
the competitive inhibitor can fit into the active site but no reaction happens
after a short time, the molecule leaves the active site
by occupying the active site for a short time, this molecule prevents the actual substrate from colliding with the active site
the frequency of collisions and successful collisions is reduced which means rate of reaction is decreased
the effect of this molecule is to reduce the rate of reaction
how can we reduce the effect of a competitive inhibitor?
by increasing the concentration of substrate molecules
increases the chance of forming an enzyme substrate complex
is the structure of a non-competitive inhibitor similar the the normal substrate ?
no
how do non competitive inhibitors reduce the rate of reaction?
non-competitive inhibitors do not bind to the active site of an enzyme
instead they bind to a different site on the enzyme molecules (allosteric site)
when the non competitive inhibitor binds to the allosteric site the tertiary structure of the enzyme changes
this means the shape of the active site changes so it is no longer complementary to the substrates
now the substrate molecules cannot bind to the active site to form an enzyme substrate complex
and the effect of this is to reduce the rate of reaction
can the effect of a non competitive inhibitor be overcome by increasing the concentration of substrate?
no because the tertiary structure and the active site has changed shaped
