How To -Glycolysis - Biochemistry

We are starting into a new semester and that means I am getting into Biochemistry II with you guys.
Main Topic this semester will be the metabolism and from experience I can say, the most difficult part is to remember all the different steps in the many metabolic cycles our body needs to stay functioning.


Glycolysis happens generally in 10 steps and is the process of breaking down glucose into smaller sugars

The reaction itself takes place in the cytosol and after investing 2 ATP you get 4 ATP and 2 NADH

First Step: Phosphorylation of Glucose

Enzymes: Hexokinase aka Glucokinase
Components: Glucose, ATP


Hexokinase catalyses under exclusion of water the two components glucose + ATP , the product is now negatively charged and therefor caught in the cytosol

Second Step: Isomerization

Enzymes: Glucosephosphate-Isomerase
Components: Glucose-6-Phosphate


This reaction is essential for step four, because only from fructose you can derive two C3-molecules.
Without isomerization, we would get a 2C-molecule and a 4C-molecule.
This step also is stereospecific.

Third Step: Phosphorylation of Fructose-6-Phosphate

Enzymes: Phosphofructokinase
Components: Fructose-6-Phosphate, ATP


In this step, our product is being phosphorylated for the second time, from Fructose-6-Phosphate + ATP toFructose-1,6-Bisphosphate + ADP
Phosphofructokinase coordinates the speed in glycolysis - VERY INTERESTING

Fourth Step: Aldol split

Enzymes: Aldolase
Components: Fructose-1,6-Bisphosphate


The reaction produces Dihydrxyacetonphosphat (DHAP) + Glyerinaldehyd-3-Phosphate (GAP)

NOTE: DHAP & GAP are isomers of eachother, but future steps in glycolysis can only process GAP

Fifth Step: Isomerization 

Enzymes: Triosephosphate-Isomerase aka TIM
Components: DHAP, GAP


This reaction generally favours DHAP, but if the body needs energy, the reaction is gonna favour the production of GAP
TIM catalyses the change of DHAP to GAP and back, with very high efficiency

Sixth Step: Oxidation (Aldehyd group to Acylphosphate)

Enzyme: Glycerinaldehyd-3-Phosphate-Dehydrogenase aka G3PDComponents: Glycerinaldehyd-3-Phosphate, NAD+, PO4 (-III)


Glycerinaldehyd-3-Phosphate + NAD+ + PO4 (-III) are catalysed by G3PD to 1,3-Bisphosphoglycerat + NADH + H+
1,3-Bisphosphoglycerat is a high energy intermediate

Seventh Step: Production of ATP

Enzymes: Phosphoglycerat kinase
Components: 1,3 Bisphosphoglycerat, ADP


This time the kinase doesn't invest, but takes one of the phosphate groups and produces 1 ATP per molecule
So, because we have 2 molecules per 1 glucose molecule, we balance our ATP usage from step 1 and 3 byproducing 2 ATP in this step

Eigth Step: Phosphate relocation

Enzymes: Phosphoglycerat-mutate
Components: 3-Phosphoglycerat


Phosphoglycerat-mutate shifts the phosphate group from the end to the middle of our molecule
3-Phosphoglycerat to 2-Phosphoglycerat

Ninth Step: Dehydration

Enzymes: Enolase
Components: 2-Phosphoglycerat


Enolase catalyses the dehydration from 2-Phosphateglycerat to Phosphoenolpyrovat
This is the second high energy intermediate

Tenth Step: Production of ATP

Enzymes: Pyruvat kinase
Components: Phosphoenolpyruvat, ADP


Thanks to our pyruvat kinase the ADP swoops in and takes the phosphate, creating ATP and the last molecule in glycolysis, pyruvat
Once again, per 1 molecule glucose we get 2 molecule phosphoenolpyruvat - which means in glycolysis we earn a total of 2 ATP and 2 NADH :)

This tutorial was soo difficult to shorten down... I hope it helps though ._.

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