BSCI330 enzymes Flashcards
what do enzymes do
catalyze chemical reactions and work by stabilizing the reaction’s transition state
how are enzymes regulated
by covalent modifications and binding of non-substrate ligands (allosteric regulation)
what are enzymes
catalytic proteins - they speed up cellular reactions to allow life and allow you to reach equilibrium faster
what can enzymes not do
do not alter delta G
they cannot make a reaction spontaneous if it’s non-spontaneous
cannot change the thermodynamics of a system
cannot alter the concentrations of reactants and products in a reaction mixture that is at equilibrium
won’t let you get more energy per mole of reactant, you just get it faster
what is activation energy
the quantity of energy to initiate a reaction
what are some qualities for enzymes as catalysts
only required in small amounts
must be left uncharged at the end of a reaction so they can cycle back to bind more substrate
catalyzes equally the forward and reverse reactions
how do enzymes begin binding to a substrate
through a stereo-specific active site, forming an enzyme-substrate complex
stereo-specific means they recognize the 3D structure but not the mirror image structures
what forms an enzyme-product complex
substrate is chemically converted to product
product is then released and enzyme can bind another molecule of substrate
what is Vmax
the rate when enzyme is saturated with substrate
rate = Vmax*[S]/(Km + [S])
what is Km
approximately equal to the dissociation constant for the enzyme-substrate complex
low Km = enzyme has a high affinity for its substrate
what is required for the series of intermediate steps substrate molecules must pass through
3D geometry of reactants needs to be adjusted for optimal interaction
electrons among reacting atoms must begin to become redistributed
what is the transition state for a reaction
an intermediate form between product and reactant with a specific structure
how do enzymes function
by stabilizing the transition state which lowers activation energy
what are prosthetic groups
non-protein molecules which aid in some protein function
what are cofactors/coenzymes
enzyme prosthetic groups
what are molecular tunnels
some enzymes perform multiple sub-reactions that must occur at distinct active sites and these structures act as tunnels to direct the intermediate products from one active site to the next
what do molecular tunnels do
prevents diffusion of intermediates, prevents decomposition of unstable molecules, and speeds up reaction rates
what are multi-enzyme complexes
how enzymes in metabolic pathways are organized to prevent diffusion of products
what is feedback control
a product of the pathway regulates one of the earlier enzymes in the pathway (negative feedback is common)
what are irreversible inhibitors
when you add the inhibitor, it permanently shuts off the inhibitor
what are reversible inhibitors
if inhibitor is there, the protein is off - bind non-covalently to enzyme
what is a competitive ibhibitor
reversibly bind to active site and compete with substrate (only one can be in active site at a time)
what is a non-competitive inhibitor
reversibly bind away from active site to cause change in enzyme structure that lowers catalytic efficiency
what is the difference between competitive and non-competitive inhibitors
competitive:
- once inhibitor is removed, substrate can bind
- increase Km, doesn’t change Vmax
non-competitive:
- doesn’t compete with substrate
- lowers Vmax, doesn’t increase Km or affect substrate binding
