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
main enzyme in third step of glycolysis and describe process of the step
enzyme = PFK
-Enzyme binds to F-G-D in active site and ATP moleq
-enzyme catalyzes phosphate from ATP to make F-I,6-P to make 2 phosphates
-PFK is under allosteric regulation by several molecules
what does allosteric regualtion of PFK regaulte
the rate of glycolysis and thus the rest of cellular respiration too
PFK is under allosteric regaultion by what
-allosteric inhibitors (citrate + ATP)
-allosteric activator (AMP)
what nolecules is an indicator of low ATP levels when it is high
AMP
need energy, so cells convert _____
ADP + ADP -> ATP + AMP
in glycolysis in a resting muscle there is more ____ and less _______
ATP, pyruvate
glycolysis in active muscle
less ATP and more AMP which binds to PFK, so ATP can’t bind to allosteric site and has to bind to active site and be used as a substrate
check notes for fate of lactate generated by fermentation
ok
gluconeogenesis
synthesis of glucose from small organic molecules
in mammals where does gluconeogensis occur
mostly in the liver
is gluconeogenesis glycolysis run in reverse
no!
