Glycolysis I & II Flashcards
A branch of U3L2
Why is it called the ‘investment’ phase in Glycolysis I?
It’s called the investment phase because it requires ATP to produce ATP.
This is accomplished by an enzyme called substrate level phosphorylation (transferring a phosphate group).
What happens in each of the stages of Glyco. I?
The phosphate from an ATP is added to the glucose forming Glucose-6-Phosphate. This causes the ATP to convert into an ADP (activation)
Because the molecule is unstable from the additional ‘P’, it changes shapes to turn into Fructose-6-Phosphate, which is an isomer of glucose (isomerization).
Another ATP is then added to the isomer which causes it to turn into fructose-1,6-biphosphate. (activation)
The isomer then splits forming 2 molecules of PGAL (or G3P). (cleavage).
Why is Glycolysis II called the ‘Pay-off’ period?
It’s called the ‘pay-off’ period because it produces ATP and NADH (high energy molecule).
What happens in Glyco. II?
Firstly, the PGAP molecules from before gets oxidized by NAD+ and gains a free Phosphate from it to from 1,3-biphosphoglycerate (PGAP). (Activation/Redox phase)
Afterwards, each PGAP loses a phosphate to ADP which produces 2 ATP and two 3-phosphoglycerate molecules (3-PGA). (Phosphorylation phase).
After that, the 3-PGA molecules are rearranged to form 2-PGA. this is because they are unstable, so they become an isomer of 3-PGA (isomerization).
After this, the two 2-PGA molecules are dehydrated to form PEP. 2H2O gets extracted. (dehydration).
Lastly, the two 2-PGA molecules lose a Phosphate to an ADP which forms 2 ATP. It also causes the formation of 2 Pyruvate which is needed in Krebs. (substrate level phosphorylation).
How much ATP is used and created and how much NADH is created?
4 ATP is made, 2 ATP is used and 2 NADH is made by glycolysis alone.
This gives us a net profit of 2ATP.
What’s the overall reaction formula for Glycolysis?
C6H12O6 + 2ADP + 2P + 2NAD + –> 2C3H4O3 + 2NADH + 2ATP (2 pyruvate).
What happens to Pyruvate in the absence of Oxygen?
In the absence of Oxygen, Pyruvate gets fermented and oxidizes NADH into NAD so glycolysis can continue. This eventually causes lactic acid buildup.
In the prscence of oxygen, Pyruvate gets activated and turned into Acetyl-CoA and gets added to another molecule to liberate CO2.
