lecture 15 - regulation of metabolic pathways Flashcards
do chem rxns and pathways take place even if they delta G < 0
no
if reactions are thermodynamically favorable can they be wasteful to the cell or organism
yes
what are main pathways regulated by
feedback inhibition
feedback inhibition
inhibition of enzyme by a product of that reaction or metabolic pathway
when does feedback inhibition occur
when product is plentiful
what is feedback regulation a form of
negative feedback or refulation
-something is binding to enzyme and turning it off
what type of enzyme does feedbakc inhibition use
allosteric enzyme
how many binding sites does allosteric enzyme have
2 binding sites
-active site for sustrate
-allosteric site for end product (inhibitor)
what happens if too much inhibitor accumulates
pathway becomes blocked and nothing can bind to the allosteric enzyme
what happens if end product binds to allosteric site
substrate can’t bind at active ste
-active site shape is altered
what happens when product is plentiful
it inhibits the enzyme an thus metabolic pathway
example of feedback inhibition
isoleucine synthesis using threonine as first substrate of the pathway
-feedback inhibition of isoleucine synthesis by isoleucine
if there is plenty of isoleucine don’t make more
are all enzymes in a pathway allosteric
no, only slect ones
what type of forms can allosteric enzyme be
active and inactive
what are some allosteric enzymes regulated by
-allosteric inhibitor
-allosteric activators
where do allosteric activators and inhibitorsbind
at allosteric site of enzyme
what can binding of an activatir stabilize
the active form of an enzyme
what can binidng the inhibitor stabilize
the inactive form of enzyme
what do most allosterically regulated enzymes consist of
multiple polypeptide subunits
what does activator binding induce
active site to adopt the right shape to bind subtrate
what happens to Km when activatir binds
Km is lower - higher affinity for substrate enzyme turned “on” or catalysts speed up
what does inhibitor binding induce
induces active site to adopt the incorrect shape to bind substrate
what happens to Km when inhibitor binds
Km is higher - lower affinity for substrate enzyme turned “off” or catalysis slows
third step of glycolysis
-key regulatory step in cellular respiration
