Refelction 6 | biochemasterz

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Our topic for today isssssssssss…………………….

GLYCOLYSIS!!!!!!!!

One Does Not Simply learn glycolysis - One Does Not Simply learn glycolysis Boromir

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When you hear the word glycolysis ….what comes to mind????

Well lets split it up

Glyco… isn’t that like glucose

And

Lysis… doesn’t this mean splitting

So lets put it together …

The splitting of glucose

In this process we begin with the 6 carbon glucose and end with 2 molecules of 3 carbon pyruvate.

There are ten reactions which can be divided into two main stages.

ENERGY INVESTMENT STAGE & ENERGY GENERATION STAGE

In these reactions 10 enzymes are involved…

FIRST STAGE

ENERGY INVESTMENT STAGE

Here glucose is converted into glucose -6 phosphate. ATP is converted into ADP. The enzyme involved is hexokinase . This is a transferase enzyme that transfer a terminal phosphoryl group from the ATP unto the glucose. This is significant as by the addition of the phosphate group to the glucose, it activates the glucose resulting in it being unstable and this promotes the reaction. This reaction is not reversible however.

2. Then glucose-6-phosphate is converted into fructose -6-phosphate. The enzyme that catalyses this reaction is phosphohexose isomerase. This is important as an aldose sugar is being converted to a ketose sugar. This reaction is reversible.

3. After the fructose 6-phosphate is converted into fructose1,6-bisphosphate. The enzyme responsible for this reaction is phosphofructokinase-1. This enzyme is the most regulated in glycolysis . In this reaction ATP is converted into ADP. This reaction is not reversible.

4. Next the fructose 1,6- bisphosphate a 6 carbon compound is converted into glyceraldehyde 3-phosphate and Dihydroxyacetone phosphate both of which are 3 carbon compounds. The enzyme here is aldolase. The reaction is reversible.

5. Here the enzyme, triose phosphate isomerase converts the Dihydroxyacetone phosphate into glyceraldehyde 3-phosphate.At the end of this stage there are two glyceraldehyde 3-phosphate molecules.

The Second Stage

ENERGY GENERATION STAGE

6. Then the two glyceraldehyde 3-phosphate is converted into two 1,3- bisphosphoglycerate . Here oxidation and phosphorylation takes place. Oxidation is an energetically feasible reaction. NAD+ has gained a hydrogen. Glyceraldehyde 3-phosphate has lost a hydrogen and given it to the NAD + . The enzyme is glyceraldehyde 3-phosphate dehydrogenase. This reaction is the only oxidation reaction of glycolysis. This reaction is reversible.

7. The two 1,3- bisphosphoglycerate is then converted into two 3-phosphoglycerate. The enzyme that catalyses this reaction is phosphoglycerate kinase. It is a reversible reaction. Here two molecules of ADP is converted to two molecules of ATP. This is the first reaction that produces ATP.

8. Here the two molecules of 3- phosphoglycerate is converted to two molecules of 2- phosphoglycerate. The enzyme for this reaction is phosphoglycerate mutase. Firstly the 3- phosphoglycerate is converted into an intermediate called 2,3- bisphosphoglycerate and then the enzyme phosphoglycerate mutase removes the phosphate group on carbon 3 to end up with two molecules of 2- phosphoglycerate.This reaction is reversible

9. The two molecules of 2-phosphoglycerate is converted to two molecules of phosphoenol pyruvate. The enzyme for this step is enolase. There is the loss of water in this step or a dehydration reaction. The phosphoenol pyruvate has alot of energy. This reaction is reversible.

10. The two molecules of phophoenol pyruvate is then converted to two molecules of pyruvate . The enzyme here is pyruvate kinase .This reaction is the most energetically favourable in glycolysis and it is not reversible.