5a Flashcards
what are the three stages of glycolysis
stage 1: trapping glucose
stage 2: generation of 3C units
stage 3: generate ATP
stage 1 of glycolysis exp
trapping glucose:
- we put a phosphate on the primary alcohol to trap it in the cell. : we form glucose-6-phosphate
- isomerisation then occurs to go from an aldose to a ketose. : this forms fructose 6 phosphate
- phosphorylation then occurs to go from fructose 6 phosphate to fructose 1-6 bis phosphate.
whats so special about glucose 1-6 bisphosphate in stage 1 of the glycolysis steps
it allows us to cleave a 6C unit to form a 3C one.
describe stage 2 of glycolysis
this is where we use the 1-6 bisphosphate to cleave a 6C molecule into a 3C one.
the 3C units are glyceraldehyde-3-phosphate
dihydroxyacetone phosphate.
the 3C units made in stage 2 of glycolysis are similar in what way
they are isomers,
isomerisation helps us get one from the other.
these are then used to generate ATP in stage 3.
name all the things made and used in stage 3 of glycolysis
1,3BPG + ADP ( using phosphoglycerate kinase) —> 3 phosphoglycerate + ATP
3 phosphoglycerate + phosphoglycerate mutase (enzyme that swaps the phosphate and OH in the moelcule,, however they dont just swap them,, they give the molecule new ones) to give 2-phosphoglycerate
2-phosphoglycerate + enolase gives phosphoenolpyruvate (PEP)
(enolase catalyses the dehydration reaction where u remove an OH and form a double bond,, this is done with an E1CB reaction bc OH is obvs a bad LG,, and we dont want to form a good one,, we just want to remove it as it is).
PEP + ADP + pyruvate kinase forms an enol which then undergoes tautomerisartion to give the keto version ( 2 carbonyls) and this is Pyruvate!!!
in step 3 of glycolysis,, what drives the PEP + ADP reaction to form pyruvate
the tautomerisation from an enol to a keto
this makes the reaction rlly good at transferring the phosphate to ADP to from ATP.
okay whats the glycolysis overview. what do we need and what do we get from it
need:
- 1 glucose
- 2 NAD
- 2 ADP
- 2Pi
we get:
- 2 pyruvate
- 2 NADH
- 2 ATP
- 2 H2O
- H+
what do we needdddd in glycolysis
we need NAD +
bc its an oxidising agent and we need this for glycolysis to occur.
this therefore needs to be regenerated , which luckily occurs in the metabolism of pyruvate.
what does NAD+ turn into
NAD+ turns into NADH
do we care about Gibbs under standard conditions of normal Gibbs
we care abount normal gibbs bc the conc of ions in the body isnt constant,, meaning conditions arent constant so whatever the gibbs standard is,, its kinda irrelavent for us rn.
what we acc care about is 🔺G but normall,,, not standard,, this is bc conditions where glycolysis occurs at is not constant.
if a reaction has a 🔺G that is close to 0 what does this mean
it means that the reaction is basically // close to equilibrium.
this means that changing the conc of SM // PRO can reverse the direction of the reaction
when the 🔺G is rlly negative what does it mean
it means that the reaction basically occurs in that was and that way only. its not reversible.
changing the conc of SM and products will not alter the direction of the reaction!!
3 fates pyuvate can undergo
- fermentation!!
- lactic acid fermentation
- citric acid // krebs cycle
pyruvate fate: describe fermentation
forms ethanol
yeast and microorganisms make it happen
pyruvate fate: describe lactic acid fermentation
forms lactate
occurs due to microorganisms and erythrocytes.
pyruvate fate: describe citric acid // krebs cycle
u form acetylcoenzyme
this is done by plants, animals and microorganisms.
when does fermentation occur
in the absense of oxygen in yeast and microorganisms
fermmentation has 2 steps,, what happens to pyruvate in these two steps
- decarboxylation (loss of CO2)
- alcohol dehydrogenase (from aldehyde to ethanol: regenerates NAD+)
in fermentation,, pyruvate underfoes decarboxylation, what is needed for this to occur
TPP
cofactor thiamine pyrophosphate
fermentation + glycolysis need and produce what
need:
- glucose
- 2 Pi
- 2ADP
- 2H+
get:
- 2 ethanol
- 2CO2
- 2ATP
- 2H2O
what is TPP and what does it look like
TPP is the cofactor that is needed in fermentation when pyruvate undergoes decarboxylation.
its a 5 membered ring with N and S with 1 carbon between them.
what does TPP do in pyruvate fermentation
H is removed from the carbon between the N and the S. this forms an anion on the C,, which then attacks the ketone part of the pyruvate as this is more electrophilic as there are no lone pairs making the C more negative. unlike an ester.
an enol is then formed in order to neutralise the N.
then a H is removed to form an aldehyde and the TPP thing.
describe pyruvate lactic acid fermentation
u have ur pyruvate,, which then undergoes lactate dehydrogenase to form lactic acid (OH instead of the ketone bit.
this also regenerates NAD+.
