10 Glycolysis Steps With Enzymes

Glycolysis Steps With Enzymes:-Glycolysis is an enzymatic pathway of  breaking down of Glucose(6’C Compound) into two molecules of Pyruvate(3’C Compound) in order to produce ATP-which acts as an energy bank.

 

In simple:- Glycolysis= Glyco + Lysis . Here, Glyco means Glucose and Lysis means Breakdown i.e. Breakdown of Glucose molecule.

 

In this blog we are going to discuss Glycolysis Steps With Enzymes in a very simple way.

 

Glycolysis Process

The process of glycolysis involves series of 10 reactions which occurs in presence of different catalytic enzymes.

 

Infact- It is the first step of cellular metabolism followed by Kreb’s Cycle(TCA Cycle) and Oxidative phosphorylation(ETC) whose ultimate goal is to produce ATP.

 

Glycolysis is also known by second name called EMP Pathway in honour of Embden – Meyerhof – Parnas.

 

Do You Know:- The process of formation of ATP is called as phosphorylation. Glycolysis falls under substrate- level phosphorylation.

 

Glycolysis is an  outer mitochondrial process occuring  in cytosol or cytoplasm. Cytoplasm and cytosol contains all glycolysis enzymes involving in this process.

 

Glucose extracted during digestion of food is transported  by blood to cells(Cytoplasm) where its  metabolism(Breaking Down Into Simpler Forms) starts in order to produce energy which makes us alive and we become able to do works.

 

Do You Know:- Glycolysis is the common pathway of both aerobic and anaerobic respiration.

 

This is because-There is no use of oxygen or releasing of CO2 in glycolysis. That means, the oxidative process in glycolysis occurs due to the release of H+-Ion(Oxidation) only. H ion can be released in both condition wheather there is presence of Oxygen(Aerobic) OR absence of Oxygen(Anaerobic).

 

Note:After glycolysis- The presence or absence of oxygen determines whether it goes to kreb’s cycle to form ATP OR it goes to fermentation process.

 

Example of Fermentation:- The conversion of milk to curd done by Lactobacillus acidophillus.

 

This example clearly explains that- The glycolysis process occurs from microorganisms to higher animals.

 

Glycolysis is very important for nutrient cycle to maintain good health and good life.

 

Glycolysis Equation/Formula

The overall reaction of Glycolysis is represented or written as shown below:-

C6H12O6 + 2 NAD+ + 2 ADP + 2 P ➡️ 2(CH3(C=O)COOH + 2 ATP + 2 NADH + 2 H+

Here,

✓C6H12O6=Glucose

✓CH3(C=O)COOH=Pyruvic Acid

✓NADH=Nicotinamide Adenine Dinucleotide Hydrogen

✓NAD=Nicotinamide Adenine Dinucleotide 

 

Glycolysis Steps With Enzymes

There are total 10 different glycolysis steps with enzymes starting from Glucose and ending at Pyruvate or Pyruvic acid. These 10 steps of glycolysis process can be futher sub- divide into 2 phases- Energy requiring phase and Energy releasing phase.

 

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A.Energy Requiring Glycolysis Steps With Enzymes

This phase includes 5 steps out of 10. It is called so because- There is use of energy in the form of ATP’s  in first and third step of cycle.

 

In this phase, there is conversion of Glucose molecule into Dihydroxyacetone Phosphate(DHAP)  And Glyceraldehyde-3-Phosphate.

 

The Glycolysis Steps with enzymes involving in energy requiring phase are shown below:-

 

STEP 1:-

              Hexokinase

Glucose ➡️➡️➡️➡️Glucose-6-Phosphate

In this step, Phoshorylation of Glucose molecule occurs  to form Glucose-6-Phosphate in presence of Hexokinase enzyme. 

 

Hexokinase enzyme in presence of Mg catalyzes the reaction by the additon of Phosphorous to the 6th carbon of glucose.

 

This phosphorous comes from ATP i.e ATP converts into ADP. This means, Glycolysis needs energy in form of ATP as kickstart.

 

After Glucose combines with phosphorous it forms more reactive compound called Glucose-6-Phosphate.

 

Addition of Phosphorous traps the Glucose inside the cell and it can no longer bind with Glucose Transport Proteins(GLUT) and cannot leave the cell.

 

This step of Glycolysis is Irriversible.

 

STEP 2:-

                                  Isomerase

Glucose-6-Phosphate⬅️➡️Fructose-6-P                                                                 

The Glucose-6-Phosphate thus formed is converted into Fructose-6-Phosphate by Isomerase(Phosphohexose Isomerase) enzyme. This is simple isomerism reaction.

 

Glucose and Fructose both are 6 carbon compounds and are isomers of each other and phosphorous is still attached to 6th carbon.

 

This step of Glycolysis is Reversible.

 

STEP 3:-

                        Phosohofructo Kinase

Fructose-6-Phosphate⬅️➡️Fructose-1,6-Biphosphate

 

The Fructose-6-Phosphate thus formed is now converted into Fructose-1,6-Biphosphate which is more unstable in nature.

 

In this step, one Phosphorous atom is added to form Bi-Phosphate i.e ATP is converted to ADP to release Phosphrous.

 

This reaction is catalyses by the enzyme called phosphofructo kinase in presence of Mg as cofactor.This is an important step of glycolysis because this enzyme helps speed up or slows down the glycolysis process.

 

If there is less ATP in cell, then the process slows down and if there is need of more ATP then the rate increases.

 

This step of Glycolysis is Irreversible.

 

STEP 4:-

                            

Fructose-               Aldolase

1,6Biphosphate⬅️➡️DHAP+G3P

The  Fructose-1,6-Biphosphate thus formed is unstable and splits into 3 carbon containing compounds called Dihydroxy acetone Phosphate(DHAP) and Glyceraldehyde-3-Phosphate(G3P) in the presence of Aldolase enzyme.

 

These two compounds thus formed are also called Trioses.

 

This step of glycolysis is Reversible.

 

STEP 5:-

               Phosphotriose Isomerase

DHAP⬅️⬅️⬅️⬅️⬅️⬅️➡️➡️➡️➡️➡️G3P

These two compounds thus formed in 4th step are isomers of each other and are convertable.

 

Glyceraldehde-3-Phosphate goes to energy releasing phase. 

 

The remaining Dihydroxy acetone Phosphate also coverts to DHAP and  goes on further process.

 

That means- Two compounds of same isomers are formed. That is why, the energy releasing phase also occurs for 2 times.

 

This step of glycolysis is reversible.

 

B.Energy Releasing Glycolysis Steps With Enzymes

This phase includes  remaining 5 steps of Glycolysis. It is called so because- There is release  of energy in the form of NADH in 6th step  and ATP’s in  7th and 10th step of cycle.

 

In this phase, there is conversion of Glyceraldehyde-3-Phosphate molecule into Pyruvic acid.

 

Also,Didhydroxyacetone Phosphate converts into G3P which ultimately forms pyruvic acid. Thus, Energy releasing phase occurs 2 times for one Glucose molecule.

 

The energy releasing steps of glycolysis with enzymes are explained below:-

 

STEP 6:-

           Dehydrogenase

G3P⬅️⬅️➡️➡️1,3-Biphospho Glycerate

This step involves the conversion of G3P into 1,3-BiPG in presence of G3P dehydrogenase enzyme. 

 

As it involves Dehydrogenase enzyme, One H-ion is released(Oxidation) from G3P. The vacant position thus formed by the release of H-Ion is filled up by the addition of Phosphorous.

 

Addition of phosphorous makes 2 Phosphates in Glyceraldehyde forming Bi-Phosphoglcerate. The phosphate group are attached to 1st and 3rd  carbon.

 

Note:- The phoshorous that is added to G3P doesn’t come from ATP.

 

In this step, the  H+ ion  thus released  combines with NAD+ and converts into NADH and H+.

 

Here, NAD+ acts as coenzyme to make the reaction go forward.Also, there is use of inorganic phosphrous(pi) in this step.

 

Note:- The NADH thus formed should again be oxidized into NAD+. If NAD+ is not available, then the cycle stops or slows down.

 

This step of glycolysis is Reversible.

 

STEP:-7

                                         Kinase

1,3-Biphosphoglycerate⬅️➡️3-PG

In this step, the phosphorous at 1 carbon postion of 1,3-BiPG  releases out to form 3-PhosphoGlycerate in presence of  phosphoglycerate kinase enzyme.

 

The phosphorous thus released combines with ADP and forms ATP. This is an example of substrate level phosphorylation.

 

This step of glycolysis is  Reversible.

 

STEP:-8

                                     Mutase

3-Phosphoglycerate⬅️⬅️➡️➡️2-PG

3-PG thus formed is converted into 2-PhosphoGlycerate in presence of Phosohoglycerate Mutase enzyme.

 

This is also isomerism reaction which involves the transfer of Phosphorous group from 3rd carbon to 2nd carbon.

 

This step of glycolysis is Reversible.

 

STEP:-9

        Enolase

3-PG ⬅️➡️ Phosphoenol     Pyruvate

This is dehydration reaction(One H2O Molecule Removes) which involves the conversion of 3-PG into Phosphoenol pyruvate in presence of enolase enzyme.

This step of glycolysis is Reversible.

 

STEP:-10

                                        Kinase

Phosphoenol Pyruvate⬅️➡️Pyruvate

This is the last step of glycolysis which involves the formation of 3-carbon containing compound in presence of Pyruvate kinase.

 

The phosphorus atom releases out and combines with ADP to form ATP. This is also a substrate level phosphorylation.

 

Remember:- As energy releasing phase occurs 2 times, there is formation of 2 Pyruvic acid.

 

This step of glycolysis is Irriversible.

 

Glycolysis Steps Enzymes Name

As there are 10 steps of glycolysis, all steps are enzymatic. That is- There are 10 enzymes in Glycolysis. The Glycolysis steps with enzymes that works in Glycolysis Process are:-

 

STEP 1:–Hexokinase

STEP 2:–Phosphohexose Isomerase

STEP 3:–Phosphofructo kinase

STEP 4:–Aldolase

STEP 5:–Phosphotriose Isomerase

STEP 6:–Dehydrogenase

STEP7:–Phosphoglycerate kinase enzyme.

STEP 8:–Phosohoglycerate Mutase

STEP 9:–Enolase

STEP 10:–Kinase

 

Energetics In Glycolysis

Energetics of Glycolysis are ATP and NADH.The energetics of Glycolysis are explained below:-

♦️STEP 1:– Consumption of 2 ATP’s

♦️STEP 6:– Formation of 2NADH

♦️STEP 7:– Formation of 2 ATP’s

♦️STEP 10:–Formation of 2ATP

In electric transport chain, NADH helps in transport of electrones and forms 3 ATP.

THUS, 2 NADH=6ATP

 

SO, Total ATP Formation=(2×3)+2+2=10 ATP

 

As 2 ATP’s are used at start, then the NET ATP PRODUCTION=(10-2)=8 ATP’s.

 

Post Glycolysis Steps

After Glycolysis, the presence or absence of oxygen determines the forward process.

 

If oxygen is available(Aerobic)-Then, 2 molecules of pyruvic acids enters in Kreb’s Cycle to produce ATP.

 

If oxygen is not available(Anaerobic)-Then, 2 molecules of pyruvic acids enters in fermentation process to form lactate.

 

Fast Question Answer(FAQ)

1.How Many Enzymatic Steps Are Involved In Glycolysis?

➡️All the 10 Steps of Glycolysis are Enzymatic steps as all contains catalytic enzymes to keep the cycle going on.

 

2.Why Glycolysis Is Common Pathway For Both Aerobic And Anaerobic Respiration?

➡️Glycolysis is common pathway for both aerobic and anaerobic respiration because the oxidation in glycolysis doesn’t involve oxygen atom, only the release of H-ion takes place. The H-ion can be released whether there is presence of oxygen or not.

 

3.Where Does Glycolysis Takes Place?

➡️Glycolysis takes place in Cytosol or Cytoplasm of cell due to the presence of all enzyme required for the cycle.

 

4.Which Steps Of Glycolysis Are Reversible?

➡️Step 2,4,5,6,7,8 and 9 of Glycolysis are Reversible.

 

5.Which Steps Of Glycolysis  Are irreversible?

➡️Step 1,3 and 10 of Glycolysis are irreversible.

 

6.Is Each Step Of Glycolysis Is Catalyzed By An Enzyme?

➡️Yes-Each step of Glycolysis are catalyzed by an enzyme. Due to this-Glycolysis is an enzymatic process.

 

7.Which Enzymes Is The Most Important In The Process Of Glycolysis?

➡️The enzyme Phosphofructokinase is most important in Glycolysis process as it can speed up or slows the glycolysis process. Other enzymes are also equally important. Without one enzyme Glycolysis process Stops.

 

8.Which Steps In glycolysis Involve Phosphorylation?

➡️Step-7 i.e Conversion of 1,3-Biphosphoglycerate to 3-Phosphogycerate and Step-10 i.e Conversion of Phosphoenol pyruvate to pyruvate involves Phosphorylation.

 

9.What Is The Type Of Phosphorylation That Occurs In Glycolysis?

➡️Substrate level Phosphorylation occurs in Glycolysis.

 

10.How Many ATP’s Are Produced in Glycolysis?

➡️No.of ATP produced in glycolysis=10

➡️Net ATP produced in glycolysis=8

This is whole information on 10 Glycolysis Steps With Enzymes And Energetics.

 

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