Glycolysis Objectives
1. Glycolysis takes place in the cytoplasm. First stage is edergonic and uses 2
ATP. The second stage is exergonic and it generates 4 ATP. Net production
in 2 ATP
2. Aerobic generates Pyruvate from glucose. Anaerobic glycolysis must
regenerate NAD+ so it converts pyruvate to lactic acid.
3. ATP must be used before glucose can be catabolized because (1) glucose
must be activated (2) Glucose must be maintained in cell by converting it to
glucose 6 phosphate and (3) it allows for regulation of pathway (at
Hexokinase and PFK1). Steps that require ATP are step 1 (hexokinase;
glucoseglucose 6 phosphate) and step 3 (PFK1; Fructose 6
phosphateFructose 1,6 bisphosphate). Steps that create ATP are step 7
(phosphoglycerate kinase; 1,3 bisphosphoglycerate3 phosphoglycerage)
and step (Pyruvate Kinase; Phosphoenol pyruvatepyruvate). ATP
generating steps are multiplied by two because glucose produces two sets of
3 carbon chains.
4. GlucoseGlucose-6-PhosphateFructose 6 PhosphateFructose 1,6
bisphosphateDihydroxyacetone Phosphate and Glyceraldehyde 3 Phophate
(DHAP is converted to G3P)1,3 Bisphosphoglycerate 3
Phosphoglycerate2 PhosphoglyceratePhosphoenol
PyruvatePyruvateLactate (only in anaerobic metabolism)
5. 1. Hexokinase(extrahepatic tissue)/Glucokinase(liver) (GG6P) 2.
Phosphoglucoisomerase 3. Phophofructokinase 4. Aldolase 5. Triose
Phophate Isomerase (DHAPG3P) 6. Glyceraldehyde 3 Phosphate
Dehydrogenase 7. Phosphoglycerate Kinase 8. Phosphoglycerate mutase 9.
Enolase (2PGPEP) 10. Pyruvate Kinase 11. Lactate Dehydrogenase.
Reaction 6 catalyzes the uptake of Pi
6. Hexokinase has a much higher affinity for glucose than glucokinase. Liver
does not use Gycolysis, glucokinase is used for Glycogen Synthesis
7. 3 Regulatory Enzymes—1. Hexokinase 2. Phosphofructokinase 1 3. Pyruvate
Kinase
8. (a) DHAP is converted to G3P in glycolysis to produce energy. (b) DHAP is
reduced by NADH giving rise to Glycerol 3 Phophate, which the base for lipid
synthesis. (c) DHAP is reduced by NADH to glycerol 3 phosphate which is
then converted back to DHAP by a mitochondrial enzyme that oxidizes FAD
to transfer protons from the cytoplasm to the ETC.
9. Cleavage of phosphate bonds in glycolysis releases enough energy to create
ATP.
10. Reaction 6—Glyceraldehyde 3 Posphate to 1,3 bisphosphoglycerate by
Glyceraldehyde 3 Phosphate Dehydrogenase
11. Reaction 11—Lactate dehydrogenase in anaerobic. In aerobic, NAD+ is
regenerated by the shuttle systems
12. Primary rate controlling step is PFK-1. It is very dependant on the need for
ATP. ATP and Citrate are an allosteric inhibitor. High [H] will turn PFK1 off
as well. AMP and Fructose 2,6 bisphosphate will upregulate PFK1.
13. Redox couples! NAD/NADH=-0.32V 3 Phosphoglycerage/Glyceraldehyde
3 Phosphate=-0.55V
Eo=-0.32 –(-0.55)=+0.22V deltaG=nFdelta E
Therefore HUGE Value for deltaG=-10.45Kcal Highly exergonic
14. Irreversible reactions—hexokinase, phosphofructokinase, and pyruvate
kinase
15. (a) 2 ATP in anaerobic (b) 30-32 ATP in aerobic
16. (a) 2 NADH in aerobic (b) 0 NADH in anaerobic
17. The shuttles take the hydrogen’s associated with NADH and bring them into
the mitochondrial matrix for use within the ETC. (a) Glycerophosphate
Shuttle uses a mitochondrial glycerol phosphate dehydrogenase, which uses
FAD as a coenzyme. Hydrogens go right to CoQ. (b) Malate/Aspartate;
Oxaloacetate is convereted to malate then transported across mitochondrial
membrane using an alphaKG/Malate Antiporter. Malate then produces OxAc
by malate dehydrogenase in IMS. OxAC is converted to alpha KG by
Apspartate Aminotransferase and is then antiported out using same
antiporter. Aspartate is antiported out using an Glutamate/Aspartate
Antiporter where the alpha KG is then converted to OxAc using Asp.
Aminotransferase.
18. Pyruvateacetaldehyde and CO2Ethanol Reaction from
AcetaldehydeEthanol regenerates NAD
19. Ethanol is metabolized by oxidizing EtOH using NAD to create acetaldehyde
then it is oxidized again by NAD to create Acetic Acid (AcetylCoAF.A.)
20. Hypoglycemia and Lactic Acidosis. Any process that needs NAD will be put
on hold. Lactic Acid won’t be converted to Pyruvate and will lead to Lactic
Acidosis. No glycolysis therefore hypoglycemia.