Glycolysis is first stage of aerobic (and anaerobic) respiration. It is a metabolic process where sugar gets turned into energy and other compounds, just take a look at the greek terminology Glyco (sweet= sugar) and lysis (break down).
There are ten steps in glycolysis but there are only two committed steps
The first five steps are the preparatory phase where ATP is used to break down glucose into two triodes.
The next five steps are the yielding phase where we it yields 2 ATP, 2 pyruvate, and 2 NADH.
Here is a brief summary of each step.
STEP 1
Glucose + ATP -> Glucose 6-phosepahate + ADP
Glucose ring is phosphorylated by Hexokinase. Phosphorylation is the process of adding a phosphate group to a molecule derived from ATP. As a result, at this point in glycolysis, 1 molecule of ATP has been consumed.This step also needs Mg(2+) and investment of 1 ATP molecule, making this a key regulatory step.
STEP 2
Glucose 6-phosepahate -> Fructose 6- phosphate
Glucose 6-phosepahate is converted to Fructose 6- phosphate. This step uses phosphoglucoisomerase.
STEP 3
Fructose 6-phosphate + ATP -> Fructose1, 6-biphosphate + ADP
Phospjorylation of fructose 6-phosphate by phosphofructokinase(PFK). This step also needs Mg(2+) and investment of 1 ATP, making this a key regulatory step.
STEP 4
Fructose 1,6 bisphosphate-> Dihydroxacetonephosphate + Glyceraldehyde 3-phosphate
The rings of the fructose then open up and the aldolase splits the fructose 1,6-bisphosphate into two trioses.
STEP 5
Dihydroxyacetonephosphate and Glyceralde 3-phosphate do reversible conversions by triosephosphate isomerase.
Dihydroxyacetonephosphate and Glyceraldehyde 3-phosphate are structur-al isomers. The equilibrium is towards glyceraldehyde 3-phosphate because it is utilized by the next five steps of glycolysis rapidly.
STEP 6
Glyceraldehyde 3- phosphate+ Pi (inorganic phosphate)+ 2NAD(+) -> 2NADH + H(+) + 2 (1,3- Bisphosphoglycerate)
Oxidation of Glyceraldehyde 3- phosphate (G3P) and phosphorytion to generate 1,3-bisphosphoglycerate (BPG) by triose phosphate dedrogenase. One proton (H+) and two electrons are removed (oxidation) from G3P.
STEP 7
2(1,3-Bisphosglycerate)+ 2 ADP -> 2ATP + 2 (3-Phosphoglycerate)
Transferring high energy phosphate group from 1,3 BPG to ADP (Substrate level phosphoration) to create ATP and 3-Phosphoglycerate . This is the first ATP yielding step.
STEP 8
2(3-Phosphoglycerate)-> 2 (2-Phoshoglycerate)
Transfer of phosphate from the 3rd to the 2nd carbon by Phosphoglyceromutase.
STEP 9
2 (2-Phoshoglycerate)-> 2 H2O + 2 (Phosphoenolpryuvate)
Removal of H2O from 2-Phosphoglycerate by Enolase. It creates a double bond between the 2nd carbon and 3rd carbon to make the phosphate bond unstable in the new compound phosphoenolpyruvate (PEP).
STEP 10
2 (Phosphoenolpryuvate) + 2 ADP -> 2 Pyruvate + 2 ATP
The phosphate from phosphoenolpyruvate is transferred to ADP (second substrate level phosphorylation) to generate two more ATPs which is the net ATP synthesis in cytoplasm during glycolysis. This is where the net gain of two ATP comes from.
Here is a video that may clear up some of the concepts
There are ten steps in glycolysis but there are only two committed steps
The first five steps are the preparatory phase where ATP is used to break down glucose into two triodes.
The next five steps are the yielding phase where we it yields 2 ATP, 2 pyruvate, and 2 NADH.
Here is a brief summary of each step.
STEP 1
Glucose + ATP -> Glucose 6-phosepahate + ADP
Glucose ring is phosphorylated by Hexokinase. Phosphorylation is the process of adding a phosphate group to a molecule derived from ATP. As a result, at this point in glycolysis, 1 molecule of ATP has been consumed.This step also needs Mg(2+) and investment of 1 ATP molecule, making this a key regulatory step.
STEP 2
Glucose 6-phosepahate -> Fructose 6- phosphate
Glucose 6-phosepahate is converted to Fructose 6- phosphate. This step uses phosphoglucoisomerase.
STEP 3
Fructose 6-phosphate + ATP -> Fructose1, 6-biphosphate + ADP
Phospjorylation of fructose 6-phosphate by phosphofructokinase(PFK). This step also needs Mg(2+) and investment of 1 ATP, making this a key regulatory step.
STEP 4
Fructose 1,6 bisphosphate-> Dihydroxacetonephosphate + Glyceraldehyde 3-phosphate
The rings of the fructose then open up and the aldolase splits the fructose 1,6-bisphosphate into two trioses.
STEP 5
Dihydroxyacetonephosphate and Glyceralde 3-phosphate do reversible conversions by triosephosphate isomerase.
Dihydroxyacetonephosphate and Glyceraldehyde 3-phosphate are structur-al isomers. The equilibrium is towards glyceraldehyde 3-phosphate because it is utilized by the next five steps of glycolysis rapidly.
STEP 6
Glyceraldehyde 3- phosphate+ Pi (inorganic phosphate)+ 2NAD(+) -> 2NADH + H(+) + 2 (1,3- Bisphosphoglycerate)
Oxidation of Glyceraldehyde 3- phosphate (G3P) and phosphorytion to generate 1,3-bisphosphoglycerate (BPG) by triose phosphate dedrogenase. One proton (H+) and two electrons are removed (oxidation) from G3P.
STEP 7
2(1,3-Bisphosglycerate)+ 2 ADP -> 2ATP + 2 (3-Phosphoglycerate)
Transferring high energy phosphate group from 1,3 BPG to ADP (Substrate level phosphoration) to create ATP and 3-Phosphoglycerate . This is the first ATP yielding step.
STEP 8
2(3-Phosphoglycerate)-> 2 (2-Phoshoglycerate)
Transfer of phosphate from the 3rd to the 2nd carbon by Phosphoglyceromutase.
STEP 9
2 (2-Phoshoglycerate)-> 2 H2O + 2 (Phosphoenolpryuvate)
Removal of H2O from 2-Phosphoglycerate by Enolase. It creates a double bond between the 2nd carbon and 3rd carbon to make the phosphate bond unstable in the new compound phosphoenolpyruvate (PEP).
STEP 10
2 (Phosphoenolpryuvate) + 2 ADP -> 2 Pyruvate + 2 ATP
The phosphate from phosphoenolpyruvate is transferred to ADP (second substrate level phosphorylation) to generate two more ATPs which is the net ATP synthesis in cytoplasm during glycolysis. This is where the net gain of two ATP comes from.
Here is a video that may clear up some of the concepts
After all the steps are completed the pyruvate continues to the acetyl CoA Formation/Lactic acid fermentation / ethanol fermentation. Keep in mind that glycolysis can take occur in the presence or absence of oxygen, so it takes place in all organisms.
Sathasivan, Kanagabapathi. Cell & Molecular Biology, An introduction 2nd Edition. Dubuque : Kendall Hunt Publishing Company, 2013 . Print.
Sathasivan, Kanagabapathi. Cell & Molecular Biology, An introduction 2nd Edition. Dubuque : Kendall Hunt Publishing Company, 2013 . Print.