glycolysis Flashcards
which enzyme is the gatekeeper of glycolysis?
phosphofructokinase 1
how do redox reactions provide a basis for energy transduction?
the electrons that fly out of the molecule being oxidized (glucose), can then be transferred to electron carriers, who will bring them to the mitochondria, which will then use them in the ETC
what are fuels oxidized by? what does this allow for?
-metabolic enzymes
-electrons harnessed from the oxidation can be transferred to the ETC, in order to be used to help power the cell
how many stages does metabolism take place in?
4
what are the 4 stages of metabolism?
1) glycolysis
2) krebs cycle
3) electron transport chain
4)complex 5
what does glycolysis mean?
sugar breaking
first 4 steps of glycolysis?
1)phosphorylation of glucose
2)isomerization (hexametric ring becomes ring with 5 sides)
3) phosphorylate again
4)SMASHHH
true or false, glycolysis is a fairly simple and straightforward process
false. its complex and has ,multiple steps
what are steps 6 to 10 of glycolysis?
6) oxidize/make NADH
7) dephosphorylate/make ATP
8)mutate (change carbon phosphate group attached to)
9)condense (lose H20)
10) dephosphorylate/make ATP
why is the first step of glycolysis important? what do we call it? what happens during this first step?
-we call it pump priming
-glucose is getting phosphorylated
-its important cause it generates a useful metabolite, that can then be used to generate multiple different things, including glycogen
-priming the pump is not what catalysts do, it is increasing free energy of reactants. higher baseline amount of energy. will drive forward reaction and increase its rate (cause by doing this we are decreasing delta G)
true or false, priming the pump does the same thing that a catalyst does?
false. a catalyst lowers the transition state. priming the pump hightens the baseline amount of energy of the reactants
what does the height of the transition state refer to?
determines the rate of the reaction (not its spontaneity)
true or false, glucose is the same size as its dissassembly machinery
false, machinary is massive compared to glucose
what is the link between glycolysis and cancer? how can we test this?
-cancer cells show increased glycolytic flux (more glucose getting broken down cause more glycolysis in cells)
-mutations in glycolytic enzymes found in patient tumours
-cancer linked to metabolism
-radioactive glucose test allows us to monitor where glucose goes in the body when ingested. will go towards tumours and we can visualize this
what was the initial hypothesis on the link between cancer and glycolysis?
they thought that unregulated glycolysis led to cancer but this was proven to be false
where does a cell want to control glycolysis?
-steps with big negative delta G, cause they are effectively irreversible
which enzyme of glycolysis do we control (gatekeeper of glycolysis)? what does it do?
-phosphofructokinase 1 (PFK1)
-the second phosphorylation of glycolysis
-This step is irreversible under physiological conditions, committing glucose to the glycolytic pathway.
what type of enzyme is PFK?
allosteric
what is PFK composed of?
4 separate polypeptide chains, each that are possible to perform this reaction.
true or false, PFK’s subunits switch their conformation one at a time
false. they all switch at the same time
what are the 2 conformations of PFK?
-TENSE (inactive), cant do much productive
-RELAXED (active)
what are the different binding sites for PFK? what do each do?
-S site: substrate binding site
-A site: activator can bind to active site, and stabilize active conformation
-I site: inhibitor site. when bound, activator and substrate site closed
what model explains hemoglobin?
MWC
what is the MWC model? compare it to HB
-tetramer that has 2 different states (active and inactive)
-as soon as get one ligand bound, switch directly to active state and rapidly fill.
-as soon as lose one, switch directly to inactive state and lose all
-As soon as HB loses one oxygen, quickly loses all. as soon as gains one oxygen, quickly saturates. this process is very important for animals like humans
what is the configuration of hemoglobin?
tetramer (4 irons in it, which can each bind to an oxygen)
which one of these graphs represents the behaviour of an allosteric enzyme and the behaviour of a non-allosteric enzyme?
blue: non allosteric
orange: allosteric
why is hemoglobin said to act like an allosteric enzyme (even though its not an enzyme)
because it exhibits cooperative binding properties. when one oxygen binds, conformational change in Hb molecule that leads it to quickly binding 3 more oxygens
what is PFK inhibited by?
its products, ATP and citrate
what can block product inhibition in PFK?
cancer mutations
whats a kinase? give an example?
-enzyme that transfers phosphate group from an ATP to another substrate (phosphorylation)
-PFK is a kinase (therefore it requires ATP)
what is the issue with PFK and ATP?
-ATP is both an inhibitor of PFK, and a requirement for it to function (since PFK is a kinase)
-we need perfect amount of it, for PFK to work, but for it to not be shut down
true or false, cancer mutations can also affect the inhibition activity of PFK
TRUE
what is PFK activated by?
-AMP
-fructose-6-phosphate
why is PFK1 activated by AMP?
-high AMP signals depletion in ATP (therefore we want PFK1 to be active, in order to produce more ATP)
-when ATP is broken down, it produces ADP, and 2 ADP associate to form AMP
why is PFK1 activated by fructose-6-phosphate?
-lots of fructose-6-phosphate signals lots of glucose present in the cell
-PFK2 turns fructose-6-phosphate into fructose 2,6-biphosphate, which activates PFK1
-INDIRECT
why is the control PFK1 important
its important to be able to turn glycolysis on and off depending on cellular needs
how do cells monitor their disassembly machines?
by conformational switching modulated by allosteric activators and inhibitors
