10 steps of glycolysis - Lecture notes 1-20 PDF

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Summary

All of the glycolytic steps needed for Exam I - IV for Silviera biochemistry....

Description

Panel 13–1 Details of the 10 steps of glycolysis For each step, the part of the molecule that undergoes a change is shadowed in blue, and the name of the enzyme that catalyzes the reaction is in a yellow box.

Glucose is phosphorylated by ATP to form a sugar phosphate. The negative charge of the phosphate prevents passage of the sugar phosphate through the plasma membrane, trapping glucose inside the cell.

CH2O P

CH2OH

Step 1

O

O

hexokinase

+

OH HO

+

ATP

OH HO

OH OH

+

H+

OH

glucose

glucose 6-phosphate

H

O

Step 2

A readily reversible 6 CH2O P rearrangement of 5 the chemical O structure (isomerization) 4 1 moves the OH OH carbonyl oxygen HO 3 2 from carbon 1 to carbon 2, forming OH a ketose from an aldose sugar. (ring form) (See Panel 2–3, pp. 70–71.)

ADP

OH

C1

1CH2OH

H

C

OH

HO

C

H

H

C

OH

H

H

C

OH

H

2

3

4 5

phosphoglucose isomerase

2

HO

6 CH2O P (open-chain form)

3 4 5

C

O

C

H

C

OH

C

OH

P OH2C 6

1

HO

5

3

4

2

OH

OH (ring form)

6CH2O P (open-chain form)

glucose 6-phosphate

CH2OH

O

fructose 6-phosphate

Step 3

The new hydroxyl group on carbon 1 is phosphorylated by ATP, in preparation for the formation of two three-carbon sugar phosphates. The entry of sugars into glycolysis is controlled at this step, through regulation of the enzyme phosphofructokinase.

P OH2C

CH2OH

O

phosphofructokinase

+

HO

CH2O P

O

ADP

+

H+

OH

OH OH

fructose 6-phosphate

P OH2C

+

HO

OH

fructose 1,6-bisphosphate

Step 4

The sixcarbon sugar is cleaved to produce two three-carbon molecules. Only the glyceraldehyde 3-phosphate can proceed immediately through glycolysis.

P OH2C

ATP

CH2O P

O

HO

CH2O P

CH2O P

C

O

C

O

C

H

C

H

aldolase

HO

HO H

C

OH

H

C

OH

H

OH OH (ring form)

H

+

O C

H

C

OH

CH2O P

CH2O P (open-chain form) dihydroxyacetone phosphate

fructose 1,6-bisphosphate

Step 5

The other product of step 4, dihydroxyacetone phosphate, is isomerized to form glyceraldehyde 3-phosphate.

H CH2OH C

O

CH2O P dihydroxyacetone phosphate

triose phosphate isomerase

O C

H

C

OH

CH2O P glyceraldehyde 3-phosphate

glyceraldehyde 3-phosphate

Step 6

The two molecules of glyceraldehyde 3-phosphate are oxidized. The energygeneration phase of glycolysis begins, as NADH and a new high-energy anhydride linkage to phosphate are formed (see Figure 13–5).

glyceraldehyde 3-phosphate dehydrogenase

H

O C H

+

C

+

NAD+

O P

O C

Pi

OH

H

1,3-bisphosphoglycerate

O P

O

The transfer to ADP of the highenergy phosphate group that was generated in step 6 forms ATP.

C

+

C

H

C

CH2O P

CH2O P 3-phosphoglycerate

– O

O 1

H

– O

O

C

C

phosphoglycerate mutase

C

OH

2

H

C

CH2O P

2-phosphoglycerate

– O

O

The removal of water from 2-phosphoglycerate creates a high-energy enol phosphate linkage.

C

C

enolase

O P

C

CH2OH

O–

O

C C

C

pyruvate kinase

O P

H2O

phosphoenolpyruvate

– O

+

+

O P

CH2

2-phosphoglycerate

O

– O

O

C H

O P

CH2OH

3

3-phosphoglycerate

Step 9

ATP

OH

1,3-bisphosphoglycerate

The remaining phosphate ester linkage in 3-phosphoglycerate, which has a relatively low free energy of hydrolysis, is moved from carbon 3 to carbon 2 to form 2phosphoglycerate.

The transfer to ADP of the high-energy phosphate group that was generated in step 9 forms ATP, completing glycolysis.

+

ADP

OH

Step 8

Step 10

– O

O

phosphoglycerate kinase

C H

NADH

OH

CH2O P

CH2O P glyceraldehyde 3-phosphate

Step 7

+

C

ADP

+

H+

C

CH2

O

+

ATP

CH3

phosphoenolpyruvate

pyruvate

– O

O

NET RESULT OF GLYCOLYSIS

C CH2OH O

C NADH

OH HO

ATP

CH3

ATP

OH

– O

O OH

O

C ATP

ATP

NADH

ATP

ATP

C

O

CH3 glucose

In addition to the pyruvate, the net products are two molecules of ATP and two molecules of NADH.

two molecules of pyruvate

+

H+...