Glycolysis Ashley Mitchinson

Glucose - breakdown

When revising this topic always keep this in mind:O Glycolysis is the break down of

glucose into pyruvate. O There are 10 steps to glycolysis.O Glucose is a 6 carbon molecule.O Glycolysis produces ATP, NADH and

H2O.

Investment.O Glucose contains 6 carbons

in a cyclic form.O Using 1 ATP and the enzyme

hexokinase a phosphate is added to the glucose molecule on the 6th position.

O A GLUCOSE with a PHOSPHATE on the SIXTH carbon, must be named Glucose 6 Phosphate.

Remember Kinase usually refers to an enzyme which can add or take away a phosphate group!

O The enzyme phosphoglucose isomerase changes the molecule from a pyran shape to a furan shape.

O The molecule now has FIVE carbons in its cyclic chain with the PHOSPHATE still attached to the SIXTH carbon.

O It must be called fructose 6 phosphate.

Remember the structures a molecule can have are often referred to as isomers, therefore an enzyme called isomerase effects the structure of the molecule!

O With the help of another ATP molecule phosphofructokinase adds another phosphate to the 1st carbon so that both ends match.

O So now the FIVE cyclic carbon has TWO PHOSPHATES on the FIRST and SIXTH carbon.

O This molecule must be fructose 1,6 bisphosphate.

So in the ‘Investment’ step a total of 2 ATP has

been used up!

The Breakup.O Now that the molecule is

symmetrical, it can be evenly split into two THREE carbon molecules.

O Aldolase does this….

This one is created when no ATP is

required.But this one … can become… that one!

This one is created when ATP is required!

Harvest.O To continue glycolysis we need

some NAD+ plus the enzyme Glyceraldehyde phosphate dehydrogenase.

O In this step the reduction of the NAD+ takes away one of the Hydrogen in the molecule and 1 phosphate is replaced at the other end of our molecule.

O So we still have our PHOSPHATE on both ends , the FIRST and THIRD carbons, minus the HYDROGEN is…

O 1,3 bisphosphate glycerate.

Remember dehydrogenase always refers to an enzyme which helps to oxidise or reduce, which often results in a Hydrogen being moved!

From this point on always remember

there are TWO molecules of three carbon

chains!!.

O In this step we yield our first pair of ATP

O Phosphoglycerate kinase removes a phosphate from the first carbon to used in the conversion of ADP to ATP.

O The molecule we have now has just one PHOSPHATE left at the THIRD carbon so it must be 3 phosphoglcerate.Remember 2 ATP

where used in the investment step

so net yield is still o far!

O The next step is to move the phosphate from the 3rd carbon to the 2nd.

O You could say the molecule needs to mutate into a different ‘form’.

O The enzyme responsible is phosphoglycerate mutase.

O So the PHOSPHATE has moved to the SECOND carbon.

O It must be 2, phosphoglycerate.

O The enzyme enolase now removes H2O from the molecule.

O So the ENOLASE has removed the water from the molecule but we still have a PHOSPHATE left but I cant remember what numbered carbon its on now so never mind that… but wasn’t the whole point of glycolysis to create PYRUVATE??

O This must be Phosphoenol pyruvate.

We must be near the end by now?

O Finally, the enzyme pyruvate kinase removes the last phosphate to add to ADP to make ATP.

O So if you remove the PHOSPHATE from the PYRUVATE...

O It must be PYRUVATE!!So we have made 2 extra ATP…

Plus a little bit of water..

And a couple molecules of NADH…

All from 1 Glucose molecule!