Question

Describe what is happening during glycolysis. Make sure you include all compounds made and in the correct order.

Answer 1

Glycolysisi is a universal catabolic pathway that converts Glucose( C6H1206 ) into Pyruvate and the free energy released in this process is used to form high energy molecules ATP (Adenosine Triphosphate) and NADH (reduce nicotinamide adenine dinucleotide). This pathway is also called Embedden Meyerhof pathway.

Glycolysis is an oxygen independent pathway with a sequence of ten enzyme catalysed reactions.

Site of glycolysis

Most animals,Glycolysis occurs in Cytosol.

Types of Glycolysis

Aerobic glycolysis : it occurs when the oxygen amount is plenty and the end products are Pyruvate along with the production of 8 ATP molecules

Anerobic glycolysis : it occurs when the oxygen amount is low and the final product is Lactate and 2 ATP molecules

Steps

Glycolysis is an etramitochondrial pathway and is by a group of eleven enxymes. Glucose is convert into pyruvate within 10 steps.The glycolytic pathway can be divided into 2 phases.

preparatory phase:

This phase is also called Glucose activation phase. The first five steps are considered as the investment phase since they consume energy to convert Glucose into 3 carbon sugar phosphates.

the first step og glycolysis is the phosphorylation of glucose by a family of enzymes called hexokinases to form glucose 6 phosphate(G6P) .This reaction consumes ATP, but it acts to keep the glucose concentration low, promoting continous transport of glucose into the cell through the plasma membrane transporters.Glucose may alternatively be formed by the phosphorolysis or hydrolysis of intra cellular strach or glycogen.

G6P is then rearranged into Fructose 6 phosphate by glucose phosphate isomerase.Fructose can also enter the glycolytic pathway by phosphorylation at this point.

step : uptake and phosphorylation of glucose

- Glucose is phosphorylated to form Glucose 6 phosphate

- The reaction is catalysed by specific enzyme Glucokinase in liver cells,buy nin specific enzyme hexokinase in the liver.The enzyme splits ATP into ADP nad Pi is added on to the glucose

step 2 : isomerisation of Glucose 6 phosphate into fructose 6 phosphate

- Hexokinase is a key glycolytic enzyme- Glucose 6 phosphate is isomerase into Fructose 6 phosphate by phosphohexo isomerase.This reaction involves an alsode ketose isomeristation catalysed by phosphohexo isomerase.there is the opening of glucopyranose ring og glucose 6 phosphate to a linear structure which then changes into furanose ring structure of Fructose 6 phosphate

step3: phosphorylation

-Fructose 6 phosphate is further phosphorylated into Fructose , 1,6 biphosphate.

- The enzyme is phosphofructokinase 1.it calatyses the transfer of phosphate group from ATP to Fructose 6 phosphate.

- the reaction is irreversible and 1 ATP ia utilised for phosphorylation.

- phosphofructokinase 1 is the key enzyme in glycolysis which regulates the break down of glucose.

step 4: clevage

- The 6 carbon fructose 1,6 biphosphate is cleaved into two 3 carbon units, one glyceraldehyde 3 phosphate(GAP) and another molecule of Dihydroxy acetone phosphate(DHAP)

-the enzyme which catalyses the reaction is Aldolase.-this reaction is reversible.

step 5: interconversion of Triphosphates

triosephosphate isomerase converts DHAP into GAP useful for generating ATP

- glucose is now cleaved into 2 molecules glyceraldehyde 3 phosphate, the reaction is rapid and reversible.

step 6: oxidative phosphorylation

- oxidation of glyceralde 3 phosphate into 1,3 biphosphoglycerate.

-the reaction is catalysed by glyceraldehyde 3 phosphate dehydrogenase.

-this is energy yeilding reaction , NAD+ is reduced to NADH

-This is a reversible reaction.

step 7: conversion

-the enzyme phosphoglycerate kinase transfers the high energy phosphoryl group from the carboxyl group.

1,3 biphosphoglycerate to ADP forming ATP and 3 phosphoglycerate.

- 3 phosphoglycerate is isomerised to 2 phospho glycerate by shifting the phosphate group from 3rd to 2nd carbon atom.- the enzyme is phosphogluco mutase

-this is a readily reversible reaction

-Mg2+ is essential for this reaction

step 8: Dehydration

- 2 phosphoglycerate is converted into phosphoenol pyruvate by enolase .- one water molecule is removed.

- A high energy phosphate bond is produced.

- enolases requires Mg++

step 9: conversion of phosphoenol pyruvate to pyruvate

-phosphoenol pyruvate (pep) is dephosphorylated to pyruvate by pyruvate kinase,

- one molecule of ATP is generated during this reaction

--this step is irreversible.