Glycolysis Flashcards
glycolysis overview
glucose (6 carbon sugar) is broken down into 2 pyruvates (3 carbons) and ATP (energy)
where does glycolysis happen?
cytoplasm of ALL CELLS
does glycolysis need oxygen?
NO
2 phases of glycolysis
energy consuming phase (uses ATP)
energy producing phase (produces ATP and reduced NADH)
what can NADH be used for?
creating ATP
after eating, glucose must be moved from where to where?
from the small intestine to the bloodstream uses GLUTs (glucose transporters)
where are GLUTs located?
cell membrane
GLUT2
liver and pancreas
more responsive to glucose in the presence of insulin
how do we keep glucose in the cell once GLUTs bring it there?
kinases (hexokinase and glucokinase) phosphorylate glucose at C6 (changes shape so it can’t easily diffuse out of the cell)
this initial phosphate comes from breakdown of ATP to ADP
we are at -1 ATP!
Glycolysis step 1
Glucose to Glucose-6-phosphate
enzyme: hexokinase/glucokinase phosphorylates glucose at C6
keeps glucose inside cell!
hexokinase vs glucokinase
hexokinase: found in all cells
glucokinase: induced by insulin
- found in liver and pancreas
Glycolysis step 2
glucose-6-phosphate to fructose-6-phosphate
enzyme: phosphoglucoisomerase
Glycolysis step 3
fructose 6-phosphate to fructose 1,6-bisphosphate
enzyme: phosphofructokinase-1 (PFK1) adds phosphate to C1 on fructose
uses ATP as phosphate source
-2 ATP!
rate determining step of glycolysis?
Phosphofructokinase 1 (PFK1)
what regulates PFK1?
PFK2!
PFK2 phosphorylates fructose-6-phosphate at C2, making fructose 2,6-bisphosphate
PFK2 regulation well fed
well fed = increase in insulin = increase in PFK2 = more fructose-2,6-bisphosphate = more PFK1 = more glucose to more energy
PFK2 regulation fasting
fasting = increase in glucagon = inhibits PFK2 = less fructose-2,6-bisphosphate = inhibits PFK1 = less glycolysis
what else controls PFK1?
high energy state = lots of ATP and citrate = inhibition of PFK1
we have enough energy, don’t need to make more
glycolysis step 4
glucose 1,6-bisphosphate to glyceraldehyde 3-phosphate (G3P) and dihydroacetone-phosphate (DHAP)
enzyme: aldolase cleaves
difference between G3P and DHAP
only G3P can go down glycolysis pathway
glycolysis step 5
DHAP to G3P
enzyme: isomerase
1 glucose: 2 G3P
glycolysis step 6
glyceraldehyde-3-phosphate to 1,3-bisphosphoglycerate
enzyme: G3P dehydrogenase
- removes H from G3P and gives H to NAD+
- makes NADH as a by product
- also adds phosphate to C1 of G3P
we have 2 (1,3-BPG) so we end up with 2 NADH that enter electron transport chain
what happens to NADH from G3P dehydrogenase rxn?
2 NADH go onto electron transport chain and go on to make 3 ATP each
glycolysis step 7
1,3-bisphosphoglycerate to 3-phosphoglycerate
enzyme: phosphoglycerate kinase
-removes phosphate from 1,3-BPG and gives it to ADP to make ATP
2 ATP made here (it happens twice)
