Glycolysis- 10 steps explained steps by steps with diagram 4.7/5 (1,233)

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Glycolysis- 10 steps explained steps by steps with diagram

Glycolysis- 10 steps explained steps by steps with diagram

Glycolysis is the metabolic process that serves as the foundation for both aerobic and anaerobic cellular respiration. In glycolysis, glucose is converted into pyruvate. Glucose is a six- memebered ring molecule found in the blood and is usually a result of the breakdown of carbohydrates into sugars. It enters cells through specific transporter proteins that move it from outside the cell into the cell’s cytosol. All of the glycolytic enzymes are found in the cytosol.

The overall reaction of glycolysis which occurs in the cytoplasm is represented simply as:

C6H12O6 + 2 NAD+ + 2 ADP + 2 P —–> 2 pyruvic acid, (CH3(C=O)COOH + 2 ATP + 2 NADH + 2 H+

Step 1: Hexokinase

step1-Glycolysis

The first step in glycolysis is the conversion of D-glucose into glucose-6-phosphate. The enzyme that catalyzes this reaction is hexokinase.

Details:

Here, the glucose ring is phosphorylated. 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.

The reaction occurs with the help of the enzyme hexokinase, an enzyme that catalyzes the phosphorylation of many six-membered glucose-like ring structures. Atomic magnesium (Mg) is also involved to help shield the negative charges from the phosphate groups on the ATP molecule. The result of this phosphorylation is a molecule called glucose-6-phosphate (G6P), thusly called because the 6′ carbon of the glucose acquires the phosphate group.

Step 2: Phosphoglucose Isomerase

step2-Glycolysis

The second reaction of glycolysis is the rearrangement of glucose 6-phosphate (G6P) into fructose 6-phosphate (F6P) by glucose phosphate isomerase (Phosphoglucose Isomerase).

Details:

The second step of glycolysis involves the conversion of glucose-6-phosphate to fructose-6-phosphate (F6P). This reaction occurs with the help of the enzyme phosphoglucose isomerase (PI). As the name of the enzyme suggests, this reaction involves an isomerization reaction.

The reaction involves the rearrangement of the carbon-oxygen bond to transform the six-membered ring into a five-membered ring. To rearrangement takes place when the six-membered ring opens and then closes in such a way that the first carbon becomes now external to the ring.

Step 3: Phosphofructokinase

step3-Glycolysis

Phosphofructokinase, with magnesium as a cofactor, changes fructose 6-phosphate into fructose 1,6-bisphosphate.

Details:

In the third step of glycolysis, fructose-6-phosphate is converted to fructose- 1,6-bisphosphate (FBP). Similar to the reaction that occurs in step 1 of glycolysis, a second molecule of ATP provides the phosphate group that is added on to the F6P molecule.

The enzyme that catalyzes this reaction is phosphofructokinase (PFK). As in step 1, a magnesium atom is involved to help shield negative charges.

Step 4: Aldolase

step4-Glycolysis

The enzyme Aldolase splits fructose 1, 6-bisphosphate into two sugars that are isomers of each other. These two sugars are dihydroxyacetone phosphate  (DHAP) and glyceraldehyde 3-phosphate (GAP).

Details:

This step utilizes the enzyme aldolase, which catalyzes the cleavage of FBP to yield two 3-carbon molecules. One of these molecules is called glyceraldehyde-3-phosphate (GAP) and the other is called dihydroxyacetone phosphate (DHAP).

Step 5: Triphosphate isomerase

step4-Glycolysis - Copy

The enzyme triophosphate isomerase rapidly inter- converts the molecules dihydroxyacetone phosphate (DHAP) and glyceraldehyde 3-phosphate (GAP). Glyceraldehyde phosphate is removed / used in next step of Glycolysis.

Details:

GAP is the only molecule that continues in the glycolytic pathway. As a result, all of the DHAP molecules produced are further acted on by the enzyme triphoshpate isomerase (TIM), which reorganizes the DHAP into GAP so it can continue in glycolysis. At this point in the glycolytic pathway, we have two 3-carbon molecules, but have not yet fully converted glucose into pyruvate.

Step 6: Glyceraldehyde-3-phosphate Dehydrogenase

step5-Glycolysis

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) dehydrogenates and adds an inorganic phosphate to glyceraldehyde 3-phosphate, producing 1,3-bisphosphoglycerate.

Details:

In this step, two main events take place: 1) glyceraldehyde-3-phosphate is oxidized by the coenzyme nicotinamide adenine dinucleotide (NAD); 2) the molecule is phosphorylated by the addition of a free phosphate group. The enzyme that catalyzes this reaction is glyceraldehyde-3-phosphate dehydrogenase (GAPDH).

The enzyme GAPDH contains appropriate structures and holds the molecule in a conformation such that it allows the NAD molecule to pull a hydrogen off the GAP, converting the NAD to NADH. The phosphate group then attacks the GAP molecule and releases it from the enzyme to yield 1,3 bisphoglycerate, NADH, and a hydrogen atom.

Step 7: Phosphoglycerate Kinase

step6-Glycolysis

Phosphoglycerate kinase transfers a phosphate group from 1,3-bisphosphoglycerate to ADP to form ATP and 3-phosphoglycerate.

Details:

In this step, 1,3 bisphoglycerate is converted to 3-phosphoglycerate by the enzyme phosphoglycerate kinase (PGK). This reaction involves the loss of a phosphate group from the starting material. The phosphate is transferred to a molecule of ADP that yields our first molecule of ATP. Since we actually have two molecules of 1,3 bisphoglycerate (because there were two 3-carbon products from stage 1 of glycolysis), we actually synthesize two molecules of ATP at this step. With this synthesis of ATP, we have cancelled the first two molecules of ATP that we used, leaving us with a net of 0 ATP molecules up to this stage of glycolysis.

Again, we see that an atom of magnesium is involved to shield the negative charges on the phosphate groups of the ATP molecule.

Step 8: Phosphoglycerate Mutase

step7-Glycolysis

The enzyme phosphoglycero mutase relocates the P from 3- phosphoglycerate from the 3rd carbon to the 2nd carbon to form 2-phosphoglycerate.

Details:

This step involves a simple rearrangement of the position of the phosphate group on the 3 phosphoglycerate molecule, making it 2 phosphoglycerate. The molecule responsible for catalyzing this reaction is called phosphoglycerate mutase (PGM). A mutase is an enzyme that catalyzes the transfer of a functional group from one position on a molecule to another.

The reaction mechanism proceeds by first adding an additional phosphate group to the 2′ position of the 3 phosphoglycerate. The enzyme then removes the phosphate from the 3′ position leaving just the 2′ phosphate, and thus yielding 2 phsophoglycerate. In this way, the enzyme is also restored to its original, phosphorylated state.

Step 9: Enolase

step8-Glycolysis

The enzyme enolase removes a molecule of water from 2-phosphoglycerate to form phosphoenolpyruvic acid (PEP).

Details:

This step involves the conversion of 2 phosphoglycerate to phosphoenolpyruvate (PEP). The reaction is catalyzed by the enzyme enolase. Enolase works by removing a water group, or dehydrating the 2 phosphoglycerate. The specificity of the enzyme pocket allows for the reaction to occur through a series of steps too complicated to cover here.

Step 10: Pyruvate Kinase

step9-Glycolysis

The enzyme pyruvate kinase transfers a P from phosphoenolpyruvate (PEP) to ADP to form pyruvic acid and ATP Result in step 10.

Details:

The final step of glycolysis converts phosphoenolpyruvate into pyruvate with the help of the enzyme pyruvate kinase. As the enzyme’s name suggests, this reaction involves the transfer of a phosphate group. The phosphate group attached to the 2′ carbon of the PEP is transferred to a molecule of ADP, yielding ATP. Again, since there are two molecules of PEP, here we actually generate 2 ATP molecules.

Steps 1 and 3 = – 2ATP
Steps 7 and 10 = + 4 ATP
Net “visible” ATP produced = 2.

Immediately upon finishing glycolysis, the cell must continue respiration in either an aerobic or anaerobic direction; this choice is made based on the circumstances of the particular cell. A cell that can perform aerobic respiration and which finds itself in the presence of oxygen will continue on to the aerobic citric acid cycle in the mitochondria. If a cell able to perform aerobic respiration is in a situation where there is no oxygen (such as muscles under extreme exertion), it will move into a type of anaerobic respiration called homolactic fermentation. Some cells such as yeast are unable to carry out aerobic respiration and will automatically move into a type of anaerobic respiration called alcoholic fermentation.

Glycolysis- 10 steps explained steps by steps with diagram

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Glycolysis- 10 steps explained steps by steps with diagram

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The Author

Sagar Aryal

Sagar Aryal

I am Sagar Aryal, a passionate Microbiologist and the Scientific Blogger. I did my Master's Degree in Medical Microbiology and currently working as a Teaching Assistant at St. Xavier's College, Kathmandu, Nepal. I am particularly interested in research related to Medical Microbiology and Virology. Find me on Facebook, Twitter or Linkedin !!!

127 Comments

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  1. As I am a microbiology student this was very usreful and it is very easy to learn
    I am very much satisfied with this. I searced a lot in the internet but I am not satisfied.But thi I can accept ..Thank you and give u many information related microbiology.

  2. hello here.. Am joseph Nyutu, a kenyan student taking Nutrition and dietetics in Kisii University. Biochemistry is part of the curriculum subject, the Glycolis step by step explanation has been brought out so well that am able now to explain it offhead. Thank sana… find me on Facebook joseph Nyutu lare(nyutunjeri) or twitter joseph Nyutu.

  3. It’s really become easy to understand .To nicely it is explained in step

  4. Good stuff

  5. VEry easy notes thank u my God belease u

  6. Excellent, thank you very much sir,

  7. z way of explanation is great thanks

  8. This helped me in AP bio and it sucked ducks

  9. Awwwweeeeeesome explanation! Thanx a ton!

  10. its very easy to understand!thanks

  11. its very easy and simple!thanks

  12. I don’t understand the role of magnesium, can you explain it more clearly?

    1. I agree

      The role is clear that it shields the highly reactive negative charge phosphate from reacting with ADP molecules but how does the cofactor and enzyme distinguish between ADP and ATP when both have a difference of one phosphate group.

  13. Thanks for your help this is useful for students and lecturers

  14. Verrryyyyyy goooood guys
    My problem solved through this particular information

  15. Verrryyyyyy goooood guys
    My problem solved through this particular information

  16. Thanks a alot

  17. Wow the notes are too cool and easy to understand thank you so much you just saved my boilogy assingment

  18. I love the glycolysis notes. They are well explained… Thanks alot

  19. this was helpful thanku

  20. Unexplained: H2O removal from Phosphoglycerate should leave PEP and Pyruvate with 2 H. But Pyruvate has 4 H. Does 2H reenter PEP

  21. Nice. Very easy to understand.

  22. very nice. Tnks for yr contribution

  23. very simplified version am impressed.
    thank you

    1. Just what I needed. Good job

  24. how can i download this page in the form of pdf

  25. Good, i like it, keep it up

  26. thankyou sir for making it easier to understand.

  27. Very usefull notes . ..thanks a lot

  28. Thank you for this explanation which is straight forward and it is more easly understandasble

  29. well explained ..easy to understand nice work keep it up

  30. THANK YOU 4 UR GOOD WORK OF EXPLAINING TIS IN SIMPLE AND UNDERSTANDABLE WAY B BLESSED

  31. Thank you so much sir for such a nice explanation….

  32. Wow thank you very much sir,am chadrick omondi from Kenya and i really love your work its very simple to understand.Keep it up

  33. I was doing a research on steps of glycolysis and stumbled on this page. The article is well written and detailed with even more explanation i wanted.
    Thank you!

  34. Wow, thanks a lot

  35. Very nice lesson.

  36. Good discussion , I was enlightened by the specifics , Does anyone know if I could acquire a blank WI WB-42 example to use ?

  37. For each molecule of glucose two molecules of payruvic acid (payruvate) formed…

  38. I am Samaila Bulus Ogus from Nasarawa state University Keffi, Nigeria. Honestly Sir your work deserve an applaud.I now understand glycolysis pathways to the best of my ability… Thanks….. BUSKID

  39. LOVE THIS BRO TY

  40. Thank you so much, very simply explained for better understanding, was finding glycolysis steps hard to understand but on reading the way of your explanation step by step I have understood. Zipporah from Kenya ,a fourth year student taking degree in Applied Biology (Microbiology option) .

  41. nice notes plz need to sign up wth u wats the procedure

  42. Thank u sir
    This is simple and sequencial explanation. It’s helpful fr me …….

  43. Thanks Sir for these. Ur explanations helped me understand stand the ten steps more.

  44. good explanations enabled me tackle this questionteffecrvely

  45. I was worried about my tomorrows cat, this has greatly helped. thanks lots Sir, God bless

  46. I’m studying Medicine and Surgery in the University of Benin, Nigeria. My lecturer didn’t break glycolysis down the way u did. I was seriously applauded today in class because of the way I explained it to my class mates. A big thank to u Dr.

  47. Am happy to get this note
    thanks sir
    Ghana Kumasi polytechnic
    please I want to know this
    since there were two molecules of PEP,was two molecules of pyruvate compound formed?

    1. yeah, two molecules of pyruvate are formed and they all jump into citric acid cycle(kreb cycle) with the help of pyruvate dehydrogenase.

  48. Very logical way, helpful,, important, and understandable to the students and other people who learning biology,. Thanks.

  49. Wow…this is bravooooo, thank you sir

  50. Tnkz for diz provision… it’s really helpful wit main points. Kudos!

  51. thanks for the information it has been so helpful to me.

  52. Good explanation with easy language

  53. Am a student of Federal university of Agriculture,Abeokuta , Ogunstate.was taught in class but didnt have a clear understanding of it Came across this explaination i read and tried to undertand each step,it is very explanatory,easier and i got to understood it BETTER.thanks

  54. Actually with this simple explanation i think am good too go with glycolysis. Thanks alot sir

  55. The steps are very simple to understand,i really love this,keep up the Good work Doctor..Israel,Zoology Unilag

  56. keep it up, I like this notes in glycolysis

  57. Very good

  58. thanks for the A on my project xD

  59. We were taught this in Animal Nutrition course in Federal University Of Agriculture, Abeokuta, Nigeria. I explained it again for my mates using this concept, they applauded me & they bought me dinner, thanks Dr.

  60. thanks……………I really liked it

  61. Thank you sir its really simpl to understand the topic. I am happy because I have clear my topic with the help of this….thank full too u sir

  62. am so excited to see this
    it makes clear explanation and so simple
    thanks to Dr.

  63. Nice , student gain more than 90 % result by this well and good concept

  64. it has realy helped me am glad

  65. Dr you have done a very good job.for me as a lay man took work, read and explain it to my wife who is preparing for examination and she understand the topic you too grate

  66. now this is the best thing i have read so far on glycolysis.even my text book can’t explain it well.thank you very much.

  67. This is easier than the ones I’ve encountered and makes my work a lot more easy I need this for my write up and I need to explain it as well for my final year paper as an Animal Nutritionist thanks a lot DR

  68. I have actually grateful with your information…thank you

  69. Thanks for your information ,it’s so helpful to us

  70. Thanks for good notes

  71. It is very easy to understand

  72. 10q GOD BLESS YOU

  73. thak u sp much GOD BLESS YOU

  74. thankyou soo much

  75. thanks alot

  76. This is help me to understand ,
    Very informative in an easy and interesting way.
    ThanQ very much

  77. i love it.thanks so much.be blessed and provided more for easier understanding

  78. nyc explanations and understoodable

  79. It’s quite interesting to know how the glucose gotten from our diet is being metabolised to give ATP

  80. why archea can live in harsh envirnment

    1. Archea can srvive in harsh environmenatl conditions because of its specific Cell wall and cell membrane compositions.

  81. very helpful regarding reaction information

  82. nice one jst write abt the steps which are reversible nd irreversible and also abt the inhibitors

  83. Very helpful and important information

  84. it’s a helpful published document thank you Dr

  85. Its very important and helpful thankyou sir

  86. Very helpful as a student who is learning biology as part of my forensic science degree and has never done biology at a-level.

  87. very informative and help me a lot thanxxx

  88. nice work thank u dear sir

  89. Thanx…..

  90. Na good job weldone

  91. It’s really very information to all students

  92. good work…..its handy to remember

  93. Thanx for the illustration. I have a query regarding structure of glucose. You have placed hydroxyl group in structure of glucose down in first carbon. Same is the case in second carbon, but you have placed hydroxyl group in third carbon up. Does it have to be so specific? I mean, cant we place hydroxyl group in first carbon up or hydroxyl group in third carbon down? I have save same question regarding placement of hydroxyl group in 3 carbon structures ie left or right.

  94. Very well written; this process needs as many accurate interpretations as there are teachers/professors. Thank you for posting.

    1. This topic help me to understand thank you souch for posting

  95. In aerobic glucose metabolism, the oxidation of citric acid uses ADP and Mg²+, which will increase the speed of reaction: Iso-citric acid + NADP (NAD) — isocitrate dehydrogenase (IDH) = alpha-ketoglutaric acid.
    In the Krebs cycle (the citric cycle), IDH1 and IDH2 are NADP+-dependent enzymes that normally catalyze the inter-conversion of D-isocitrate and alpha-ketoglutarate (α-KG). The DH1 and IDH2 genes are mutated in > 75% of different malignant diseases. Two distinct alterations are caused by tumor-derived mutations in IDH1 or IDH2: loss of its normal catalytic activity during the production of α-ketoglutarate (α-KG) and the gain of catalytic activity to produce 2-hydroxygulatrate (2-HG).
    This product is a competitive inhibitor of multiple α-KG-dependent dioxygenases, including histone, demethylases, prolyl-4-hydroxylase and the TET enzymes family (Ten-Eleven Translocation-2), resulting in genome-wide alternations in histones and DNA methylation.
    IDH1 and IDH2 mutations have been observed in myeloid malignancies, including de novo and secondary AML (15%–30%), and pre-leukemic clone malignancies, including myelodysplastic syndrome and myeloproliferative neoplasms (85% of the chronic phase and 20% of transformed cases in acute leukemia).
    The energetic sum of anaerobic glycolysis is ΔGo = -34.64 kcal/mol. However, a glucose molecule contains 686 kcal/mol and the energy difference (654.51 kcal) remains a potential for un-controlled reactions in carcinogenesis. The transfer of electrons from NADPH in each place of the conserved unit of energy transmits conformational exchanges of mitochondrial ATPases. In the reaction, ADP³+ P²¯ + H²– ATP + H2O it is a reversible reaction. The terminal oxygen from ADP binds the atom P2¯ by forming an intermediate pentacovalent length and synthesizing the molecular complexes ATP and H2O. This reaction requires Mg²+ and ATP-synthetase, which is known as the H+-ATPase or the Fo-F1-ATPase complex, where FO is a conductor proton and F1 is synthesized.
    Mg2+ stabilizes the mitochondrial membrane via the high electronegativity of its electrons. In contrast, intracellular calcium induces mitochondrial swelling and aging. Mg2+ generally interacts with substrates via the inner coordination sphere, stabilizing anions or reactive intermediates, binding ATP and activating the molecule for nucleophilic attack.

    Dr. Aurel

  96. I’m glad to see this post, as a student of nutrition for better health and aging. How does this relate to Diabetes? Can you connect the dot for the general public? I’ve read dozens of books on diet and nutrition, but only getting confused, without conceptual biological-chemical bases to validate many contradictory claims.

  97. I am glad to see that you included the delta-G values in the principal figure. These are very important for helping students appreciate how the flow operates in these pathways, but the values are often left out of figures for the sake of simplicity. At the same time, I would recommend adding arrows for the reverse reactions, perhaps with length indicating the free energy vector, to further emphasize and distinguish the freely reversible from essentially irreversible reactions. It might also help to add both the free energy values and the reverse arrows to the single-step figures, as well. Overall, this is a pretty good study review.

    1. Nice theory

      1. Easy to understand

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