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20 Cards in this Set
- Front
- Back
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Rando: strabismus
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cross eyes
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Where within the cell does glycolysis occur?
Where else? What specific cells use glycolysis? |
cytoplasm
CYTOPLASM All of them |
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Why does the cell phosphorylate glc and its intermediates to pyr?
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PO4 traps glc in the cell
Is transferred to ADP to make ATP |
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What's the highest energy compound in the cell?
How do we take advantage of this? What else uses this system? |
PEP (phosphoenolpyruvate)
It can perform *substrate level phosphorylation* on ADP to form ATP 1,3-BPG (bisphosphoglycerate) |
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How many oxygen equivalents are needed for glycolysis?
How does this translate to the bigger picture? |
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Under ischemic conditions (like a heart attack) it is the only pathway providing ATP. |
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How would you characterize the free energy changes during glycolysis?
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All -ΔG values making reactions favorable and effectively impossible to reverse using the same mechanism/enzyme
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What's the first step of glycolysis?
What enzyme is used? |
phosphorylation of glc with an ATP
Hexokinase and/or glucokinase |
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Compare hexokinase and glucokinase
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hexokinase ---- glucokinase:
-in all tissues ----liver (minorly in pancreas) -most monosaccharides (not gal) -----only glc low Km (µM scale) ----high Km (mM scale) always working ---- 1st order activity rises with [glc] unless inhibited by G6P ---- not affected by G6P reg's cell's [glc] level ---- reg's blood [glc] by trapping excess ---- insulin stimulates |
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How is the second ATP used in glycolysis?
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F6P -----Phosphofructokinase-1--> F-1,6-bisphosphate
This is the committed step in glycolysis |
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How is PFK-1 regulated?
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Active when cells need both energy and building blocks.
In extrahepatic cells: ATP (high energy cell) inhibits citrate (since TCA cycle has backed up) inhibits AMP (low energy cell) activates |
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How many oxidative steps are there in glycolysis?
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1 when glyceraldehyde-3-P goes to 1,3 BPG making NADH and making the carbon fragment have 2 PO4's again
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What are the two reactions to produce ATP in glycolysis??
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1,3-BPG ---phoshoglycerate kinase--> 3 phosphoglycerate
PEP ----pyruvate kinase---> pyruvate |
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What are the two hallmark symptoms of pyruvate kinase deficiency and why?
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Hemolytic anemia (very common cause) and increased 2,3-BPG
RBC rely on glycolysis and hexose monophosphate shunt (stripped of organelles). Without glycolysis pathway, not enough ATP to maintain Na/K ATPase pumps, and cell shreds. (also why 5mM [glc] in blood is so important- RBC have no other choice) Because 1,3-BPG is an intermediate in glycolysis upstream of pyr formation, it builds up, and increases its conversion to 2,3-BPG by erythrocytes. 2,3-BPG is allosteric regulator of Hb to lower O2 affinity and increase O2 unloading-> poor oxygen transport to periphery |
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The special role of the liver in maintaining a constant blood [glc] requires an additional regulatory mechanism to coordinate glucose consumption and production (glycolysis vs gluconeogenesis). This is done by the powerful allosteric activator ______.
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fructose-2,6-bisphosphate
*note: not to be confused with F-1,6-P: the product of F6P --PFK-1--> in the second ATP consuming step of glycolysis* |
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When is F2,6P made? How?
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Glc abundant supply in well-fed person:
Insulin stimulates (removes PO4); glucagon down regulates (adds PO4) to PFK-2 F6P----PFK-2---> F2,6P |
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What does F2,6P do in the liver and extrahepatic tissues?
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In the liver, F2,6P stimulates PFK-1 and thereby glycolysis is is going like a model t factory. Down regulates F1,6Pase and thereby gluconeogenesis. Uses pyr to make FA.
In extrahepatic cells there is NO F2,6P or PFK-2, so after glycolysis goes for a while ATP is up, inhibiting PFK-1 and the rest of glycolysis the end. |
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How does diabetes work?
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Because the insulin signal is not received, PFK-2 is not stimulated and cannot stimulate the PFK-1 being inhibited by rising ATP levels in the liver.
In everywhere, as F6P builds and G6P behind it which inhibits hexokinase. Liver's glucokinase is insulin-dependent and not activated either. Liver doesn't trap glc to regulate blood [glc] |
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What is a precursor to NAD/NADH?
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niacin (vit B3)
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What's the general difference between NAD+ and NADP+?
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NADP+ is used in anabolic reactions+ ATP --> products
NAD+ in catabolic reactions --> ATP These two are completely distinct |
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What kinds of reactions is NAD/NADP used in?
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hydroxyl <---> aldehyde ----> carboxyl
2e- coming and going for these So these are noncovalently bound to dehydrogenases |
