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ATP Production in Glycolysis: The Basics

Updated on July 18, 2013


Glycolysis is an essential energy producing form of cellular respiration wherein glucose, a simple 6-carbon sugar also known as blood sugar, is broken down into pyruvate and energy storing molecules (ATP) for use in the cell. Glycolysis occurs in both the presence and absence of oxygen.

Glucose Molecule

Glucose Molecule
Glucose Molecule | Source


The purpose of glycolysis is to use two adenosine triphosphate (ATP) molecules to break glucose down, producing pyruvate, nicotinamide adenine dinucleotide (NADH), and more ATP molecules than were used to fund the reaction. This basic reaction is used by cells to gather ATP molecules which can then be broken down into adenosine diphosphate, releasing energy that can be utilized by the cell.

Where it Takes Place:

Glycolysis occurs in the cytosol of both prokaryotic (bacteria and archaea) and eukaryotic (plant, animal, etc...) cells.


1. Initally, the enzyme hexokinase splits a phosphate from one ATP molecule and attaches it to glucose, releasing one ADP molecule and converting glucose to glucose 6-phosphate (meaning six carbons plus a phosphate group).

2. Another enzyme called phosphoglucoisomerase rearranges the glucose 6-phosphate into fructose 6-phosphate. This is an isomer of glucose 6-phosphate, which means that nothing is added or subtracted from the glucose 6-phosphate, only arranged into different positions.

3. A new enzyme phosphofructokinase (as opposed to isomerase) transfers a phosphate group from a new ATP and attaches it to fructose 6-phosphate into fructose 1,6-biphosphate). Now two ATP molecules have been spent on glycolysis.

Hint: If an enzyme ends in "kinase," that enzyme will transfer a phosphate group from one molecule to another. If an enzyme ends in "isomerase," it will alter the structure of a molecule to create an isomer of that molecule.

4. The enzyme aldolase splits the fructose 1,6 biphosphate molecule into two three carbon molecules called dihydroxyacetone phosphate and glyceraldehyde 3-phosphate respectively.

5. the enzyme isomerase (remember phosphoglucoisomerase?) rearranges dihydroxyacetone phosphate into the isome, glyceraldehyde 3-phosphate. The cell now has two glyceraldehyde 3-phosphate molecules to work with.

6. The two molecules of glyceraldehyde 3-phosphate are oxidized (given a hydrogen/proton) by the molecule triose phosphate dehydrogenase and are are also each given a phosphate group from the cytosol to produce two molecules of 1,3-biphosphoglycerate. This reaction results in the release of two molecules of NADH + H+.

7. The enzyme phosphoglycerokinase takes one free phosphate group given to each 1,3-biphosphoglycerate molecule by trios phosphate dehydrogenase and attaches each to an ADP molecule, resulting in two molecules of ATP and changing the two 1,3-biphosphoglycerate molecules into two 3-phosphoglycerate molecules.

8. The enzyme phosphoglyceromutase moves the phosphate groups on each 3-phosphoglycerate to a new position, creating two 2-phosphoglycerate molecules.

9. Another enzyme, enolase, rips a water molecule (H2O) off of each 2-phosphoglycerate, forming two molecules of phosphoenolpyruvate.

10. Finally, the enzyme kinase transfers a phosphate from each phosphoenolpyruvate to two ADP molecules, producing two ATP molecules and leaving behind two pyruvate molecules.

Glycolysis Steps

Glycolysis Steps
Glycolysis Steps | Source


2 ATP molecules: these can be hydrolyzed (split by water) to release free energy that can be used to power other cycles and reactions.

2 NADH molecules: these can be used in oxidation/reduction (redox) reactions as a reducing agent to donate electrons to other molecules. NADH from glycolysis goes to the electron transport chain.

2 pyruvate molecules: these can be converted to acetyl CoA, which links glycolysis to other cellular respiration reactions, such as the Krebs/citric acid cycle. If you'd like to know more about how the products of glycolysis and cellular respiration continue, check out this great article on the citric acid cycle!

Terms to Know:

ADP: a molecule consisting of a 5-carbon pentose sugar, an adenine molecule, and two phosphate groups used to synthesise ATP and created as a result of ATP hydrolysis.

ATP: a molecule consisting of a 5-carbon pentose sugar, an adenine molecule, and three phosphate groups hydrolized to produce energy. Note that ATP consists of one more phosphate group than ADP

Cytosol: the thick, viscous liquid that cell organelles are suspended in, kind of like the air blown into a balloon, but much much thicker.

Enzyme: biological molecules that catalyze, or increase the speed of, biological reactions. Note that enzymes will not cause a reaction to take place if it wouldn't normally, it only causes the reaction to go faster.

Glucose: a simple sugar, called a monosaccharide, consisting of six carbons, twelve hydrogens, and six oxygens (C6H12O6) and used in glycolysis to produce ATP, NADH, and pyruvate.

Isomer: a molecule or compound with the same molecular fomula (ex. H2O) as another molecule or compound, but a different structure.

NADH: A reducing agent used in redox reactions to donate electrons to other molecules.

Oxidation: the loss of an electron or gain of a proton/hydrogen atom by a molecule.

Pyruvate: a result of glycolysis that transforms into acetyl CoA, linking glycolysis to the Krebs/citric acid cycle.

Redox Reaction: a reaction in which one reactant is oxidized and one is reduced.

Reduction: the gain of an electron or loss of a proton/hydrogen atom by a molecule.


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    • Btryon86 profile imageAUTHOR


      8 years ago

      Hi guest. I'm not sure what information you need, but I'll do my best. I'm not sure when I posted this, sometime in 2012 though, so that should be the publication date. Site name is Site pubilsher is Hubpages Inc. Article name is at the top. Use Btryon86 as the author name since that's what's shown here. Other than that, just include the link to the article.

    • profile image


      8 years ago

      i have to cite this information will you provide the your information for citation

    • ciaralw profile image


      9 years ago from San Diego, California

      This hub is very informative and you use the terminology to give the most accurate explanation of the process. If there are enough tags, (which I can't see) you can help a lot of students in particular with great information for their school projects. I love science and knowing how things work, especially when it comes to our bodies. Great Job.

    • Btryon86 profile imageAUTHOR


      9 years ago

      Thanks for your support!

    • alian346 profile image


      9 years ago from Edinburgh, Scotland

      Well - I wish you all the very best - that will be a great career with a lot of hard work involved, if qualifying where you are is anything like it is here (Scotland)!


    • Btryon86 profile imageAUTHOR


      9 years ago

      Thank you very much! I'm afraid I'm not very good at explaining things in person though! I do, however, want to become a veterinary surgeon.

    • alian346 profile image


      9 years ago from Edinburgh, Scotland

      I'm a retired chemist - my knowledge of biology is limited, I'm afraid to say - all those big words!

      I think you have a knack of explaining complex concepts in a logical and friendly fashion without scaring your reader off! And you include a glossary.

      Have you considered a career in education?


    • Btryon86 profile imageAUTHOR


      9 years ago

      Thanks for the comment, I'm glad it helped!

    • anne91 profile image


      9 years ago from india

      thanks a lot.your hub has helped me a great deal.iv got my exam tomorrow and i needed to understand glycolysis better..

    • Btryon86 profile imageAUTHOR


      9 years ago

      Thank you all for your kind comments!

    • profile image


      9 years ago

      Fantastic information on this scientific topic. Voted up and useful! Take care, Kelley

    • Daughter Of Maat profile image

      Melissa Flagg COA OSC 

      9 years ago from Rural Central Florida

      I concur with mwilliams66. Fantastic hub.

    • mwilliams66 profile image


      9 years ago from Left Coast, USA

      Brilliant explanation of a daunting topic. Easily understood and well written.


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