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Aerobic Glycolysis and the Production of Acetyl CoA


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Which cells rely on glycolysis for ATP?Why?
RBC... no mitochondria
What are the two phases of glycolysis?

What is the starting and end products of each phase?

How many ATP are made or used in each phase?
Phase I: 5 steps that break glucose down to 2 molecules of gly-3-P (uses 2 ATP)

b. Phase II: gly-3-P are converted to pyruvate (4 ATP are produced).
What does hexokinase do?
Hexokinase recognizes 6-C sugars and phosphorylates them at the 6th carbon.
What is the net ATP production of one glucose molecule in glycolysis
2 ATP (+ 3 from two NADH after being transfered across the inner mt-membrane) = 5
What is the ∆G° (std cond) for the phosphorylation of glucose to G-6-P?
∆G° = -4.0 kcal/mol
What does the rapid phosphorylation of glucose accomplish?
It traps glucose in the cell and causes the diffusion of more glucose across the membrane.
What function do GLUTS serve in glycolysis?
they are proteins which shuttle glucose quickly across the plasma membrane in a thermodynamically fashion.
What is the ∆G (phys cond) for the phosphorylation of glucose to G-6-P? and why?
a. ∆G = -8.0 kcal/mol.
b. At phys cond the [ATP]>>>[ADP]and [glucose]>>> [G-6-P]
Thus, this rxn is more likely to occur, where as at std cond the conc are the same.
What is the functionality of an enzyme's active site cleft closing? (2 parts).
1. closing the cleft off from the substrate and creating a hydrophobic environment hastens the rxn.
2. If water got into the site it would compete for phosphorylation with the glucose.
Given that the [glucose] in blood is about 4mM and the Km of hexokinase is about .1mM, what is the significance of glucokinase having a Km of 10mM?
Glucokinase is found in the liver,and is an analogue of hexokinase, so you would only get glucokinase after a glucose rich meal.
What alternate pathway does glucokinase conver glucose to G-6-P for?
conversion of glucose to Glucokinase converts glucose to glycogen when glucose levels are very high.
What will you see when an enzyme catalyzes a thermodynamically favorable process?
Enzyme regulation
What regulates the conversion of glucose to G-6-P?
allosteric inhibition of hexokinase (or glucokinase), where G-6-P is the inhibitor.
Name the 11 intermediate products in glycolysis from glucose to pyruvate.
Glyceraldehyde-3-phosphate (<-> dihyoroxy-acetone-P)
What is the name of the enzyme that converts G-6-P to F-6-P? Is this thermodynamically favorable?
a. Phosphoglucose Isomerase which changes molecule from a 6 to a 5 membered ring.
b. -6 kcal/mol (+0.4 kcal/mol)
What is the name of the enzyme that converts F-6-P to F-1,3-bisphosphate? Is this thermodynamically favorable? why?
a. phosphofructokinase-1 (PFK-1)
b. Yes, -5.3 kcal/mol (-3.4 kcal/mol)
c. already fav due to ATP driven, but more fav at phys cond due to high ATP and low ADP conc.
Which steps in glycolysis require ATP?
Step One: glucose to G-6-P
Step Three: F-6-P to F-1,3-bisphosphate.
What is the difference between di and bis phosphates?
Di: phosphate are next to each other.
Bis: P are on different ends.
Is F-6-P to F-1,3-bisP regulated? why? and how? (hint) think sigmoid curve.
a. Yes, heavily
b. controls the overall rate of glycolysis.
c. PFK-1 is allosterically inhibited by high conc of ATP... look for a sigmoid curve?
d. It is also inhibited by citrate, which is a way that the TCA cycle tells glycolysis to slow down by feedback inhibition (an end product inhibiting an earlier rxn.).

What reverses the inhibition of ATP to PFK-1? Why?
a. AMP
b. ADP + ADP --> ATP + AMP... but ATP is continued to be hydrolyzed to ADP so AMP will be higher in conc in during high energy need.
What is the first commited step in glycolysis?
F-6-P to F-1,3-BisPh... the earier step that is very fav can send G-6-P to other pathways.
What is a potent activator of the PFK-1 rxn?
F-2,6-bisPh, speeds up rxn.
a. In Step four of glycolysis, F-1,6-BisPh --> goes to?

b. what is the enzyme involved?)

c. In terms of ∆G is this rxn favorable?

d. Why is there a big difference between ∆G° na ∆G?
a. dihydroxyacetone-P and glyceraldehy-3-P

b.Fructose Bisphosphate aldolase

c. ∆G = -0.3

d. Product removal.
a. What is the enzyme involved in converting dihydroxyacetone-P to glyceraldehy-3-P?
b. Is this rxn favorable?
a.Triose Phosphate isomerase
b. neutral
What is the overall ∆G in the first phase of glycolysis?
∆G = -13.6 kcal/mol
What are the two regulatory steps of the first phase of glycolysis?
Hexokinase and PFK-1
What is the tally on ATPs in the First Phase of glycolysis.
Minus 2 ATP (2 used)
a. What is Glyceraldehyde-3-P converted to?
b. What 3 things are required?
c. Is the rxn favorable at ∆G?
a. 1,3-BPG
b. glyceraldehyde-3phosphate dehydrogenase, NAD+, P
c. ∆G = -0.4
What is the acetyl phosphate substituent on 1,3-BPG provide?
The high phosphoryl transfer potenital needed to produce ATP.
a. What is 1,3-BPG converted to?
b. what is required?
c. Is this rxn favorable at ∆G?
d. why is the ∆G different than ∆G°?
e. What is produced?
a. 3-phosphoglycerate
b. phosphoglycerate kinase, ADP
c. ∆G = 0.3 kcal/mol (∆G° = -4.5 kcal/mol)
d. As ∆G° shows the release of energy is great because it it greater than the energy releasd from hydrolysis of ATP, however you are going up the [ATP] gradient.
e. ATP
What poison blocks the conversion of 1,3-BPG to 3-phosphoglycerate?
b. why?
c. and how does in it effect ATP production?
a. Aresenate
b. behaves like a phosphate, thus it competes with the inorganic phosphate (it does not block the enzyme)
c. aresenate gets rapidly hydrolyzed and no ATP can be made because acted as an inorganic mimic.
Besides arsenate, what can happen to 1,3-BPG that prevents it from continuing on glycolytic pathway?
It can be siphoned on for use by RBC by BPG mutase, it will be hydrolyzed by water... thus no ATP is produced.
What does 2,3-BPG do in RBCs?
2,3-BPG reduces the affinity of hemoglobin for oxygen.
a. What is 3-phosphoglycerate converted to?
b. What is required for rxn?
c. Favorable?
a. 2-phosphoglycerate
b. phosphoglycerate mutase, which requires a small amount of 2,3-BPG to be active.
c. ∆G = 0.2 kcal/mol
a. What is 2-phosphoglycerate converted to?
b. What is required.
c. What type of moiety is made?
d. Is this rxn favorable?
a. phosphoenolpyruvate + water.
b. enolase
c. an enolephosphate
d. ∆G = -0.8 kcal/mol
a. In the final step of glycolysis, what is phosphoenolglycerate converted to?
b. What is required?
c. Is this favored.
d. why is ∆G° different from ∆G?
e. This is highly regulated, what inhibits and what activates?
a. Pyruvate
b. pyruvate kinase + ADP
c. ∆G = -4.0 kcal/mol and ∆G° = -7.5 kcal/mol.
d. [ADP] is low and [ATP] is high, so you're fighting these gradients.
e. Activators: AMP, fructose-1,3-bisphosphate....
e. Inhibitors: ATP acetyl CoA, alanine... activators: AMP and F1,6-BP
Which three glycolytic steps are thermodynamically favored?
1. glucose to G3P
3. F3P to F-1,6-BP
10. phosphoenolpyruvate to pyruvate.
What are the investments in glycolysis?
a. 1 glucose
b. 2 Pi
c. 2 ADP
d. 2 NAD+
What are the products of glycolysis?
a. 2 pyruvate
b. 2 ATP
c. 2 NADH
d. 2 H+
e. 2 H2O
When oxygen is present, what happens to NADH produced by glycolysis?
It is recycled it is transferred across the inner mitochondrial border --> FADH2 --> used in the ETC --> glycolysis can continue.
a. What happens in the absence of oxygen to NADH produced by glycolysis?
b. Is this thermodynamically favorable?
a. Pyruvate is converted to lactate, which will recycle NAD+.
b. yes.

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