Enzymes Flashcards
what is the function of enzymes?
to act as a catalyst.- lowers the energy of activation for a biological reaction and increasing the rate of the reaction
they are not consumed or altered by the reaction. they do not alter the equilibrium of a reaction.
lock and key theory
the active site of an enzyme has a specific shape like a lock and only fits a specific substrate (key).
this model explains some but not ALL enzymes
Induced fit model.
the shape of both the enzyme and the substrate are altered upon binding. beside increasing specificity , the alteration actually helps the reaction to proceed.
saturation kinetics
as the concentration of the substrate increases the rate of the reaction does as well, but to a lesser and lesser degree until a max rate (Vmax) has been achieved.
what is Vmax proportional to ?
the enzyme concentraiton
what is the Km?
is the substrate concentration at which the rate of the reaction is equal to half of Vmax. km dosent change when the enzyme concentration is changed. kM is a good indicator for the enzymes affinity for the substrate.
temperature and the pH also affect the enzyme reactions
when the temp increases the reaction rate will go up as well. but at some point, the enzyme denatures and the rate of the reaction drops . enzymes also function within specific ph ranges
in order to Reach their optimal activity , many enzymes require ?
non protein component which is called the co factor.
cofactors can be co-enzymes or metal ions (minerals)
co-enzymes can be vitamins or their derivatives.
what are the types of enzyme inhibitors?
irreversible inhibitors
competitive inhibitors
non competitive inhibitors
irreversible inhibitors
bind covalently and disrupt function
they can be highly toxic.
competitive inhibitors
compete with the substrate by binding reversibly with non covalent bonds to the active site. these can raise the Km but do not change the Vmax.
we can overcome this inhibition by increasing the substrate concentration
-these inhibitors often resemble the substrate
non competitive inhibitors
bind non covalently to an enzyme on a spot other then the active site and change confirmation of the enzyme. they don’t prevent the substrate from binding.they lower the Vmax. they do not lower the enzyme affinity for the substrate so the Km remains the same.
how are enzymes regulated?
proteolytic cleavage
reversible covalent modification
control proteins
allosteric interactions
what happens in proteolytic cleavage?
also called irreversible covalent modification
- many enzymes are released into the env in an inactive form as zymogen and proenzymes . when specific peptide bonds are cleaved the zymogens become irreversibly active.
what happens in reversible covalent modification?
activated or deactivated by phosphorylation or the addition of some other modifier such as AMP.
removal - via hydrolysis
phosphorylation via protein kinase
