Question

the proper sequence of stages in glycolysis is

Answer 1

STEP 1

The enzyme hexokinase phosphorylates (adds a phosphate group to) glucose in the cell's cytoplasm. In the process, a phosphate group from ATP is transferred to glucose producing glucose 6-phosphate.

Glucose (C6H12O6) + hexokinase + ATP → ADP + Glucose 6-phosphate (C6H13O9P)

STEP 2

The enzyme phosphoglucoisomerase converts glucose 6-phosphate into its isomerfructose 6-phosphate. Isomers have the same molecular formula, but the atoms of each molecule are arranged differently.

Glucose 6-phosphate (C6H13O9P) + Phosphoglucoisomerase → Fructose 6-phosphate (C6H13O9P)

STEP 3

The enzyme phosphofructokinase uses another ATP molecule to transfer a phosphate group to fructose 6-phosphate to form fructose 1, 6-bisphosphate.

Fructose 6-phosphate (C6H13O9P) + phosphofructokinase + ATP → ADP + Fructose 1, 6-bisphosphate (C6H14O12P2)

STEP 4

The enzyme aldolase splits fructose 1, 6-bisphosphate into two sugars that are isomers of each other. These two sugars are dihydroxyacetone phosphate and glyceraldehyde phosphate.

Fructose 1, 6-bisphosphate (C6H14O12P2) + aldolase → Dihydroxyacetone phosphate (C3H7O6P) + Glyceraldehyde phosphate (C3H7O6P)

STEP 5

The enzyme triose phosphate isomerase rapidly inter-converts the molecules dihydroxyacetone phosphate and glyceraldehyde 3-phosphate. Glyceraldehyde 3-phosphate is removed as soon as it is formed to be used in the next step of glycolysis.

Dihydroxyacetone phosphate (C3H7O6P) → Glyceraldehyde 3-phosphate (C3H7O6P)

Net result for steps 4 and 5: Fructose 1, 6-bisphosphate (C6H14O12P2) ↔ 2 molecules of glyceraldehyde 3-phosphate (C3H7O6P)

STEP 6

The enzyme triose phosphate dehydrogenase serves two functions in this step. First the enzyme transfers a hydrogen (H-) from glyceraldehyde phosphate to the oxidizing agent nicotinamide adenine dinucleotide (NAD+) to form NADH. Next triose phosphate dehydrogenase adds a phosphate (P) from the cytosol to the oxidized glyceraldehyde phosphate to form 1, 3-bisphosphoglycerate. This occurs for both molecules of glyceraldehyde 3-phosphate produced in step 5.

A. Triose phosphate dehydrogenase + 2 H- + 2 NAD+ → 2 NADH + 2 H+

B. Triose phosphate dehydrogenase + 2 P + 2 glyceraldehyde 3-phosphate (C3H7O6P) → 2 molecules of 1,3-bisphosphoglycerate (C3H8O10P2)

STEP 7

The enzyme phosphoglycerokinase transfers a P from 1,3-bisphosphoglycerate to a molecule of ADP to form ATP. This happens for each molecule of 1,3-bisphosphoglycerate. The process yields two 3-phosphoglycerate molecules and two ATP molecules.

2 molecules of 1,3-bisphoshoglycerate (C3H8O10P2) + phosphoglycerokinase + 2 ADP → 2 molecules of 3-phosphoglycerate (C3H7O7P) + 2 ATP

STEP 8

The enzyme phosphoglyceromutase relocates the P from 3-phosphoglycerate from the third carbon to the second carbon to form 2-phosphoglycerate.

2 molecules of 3-Phosphoglycerate (C3H7O7P) + phosphoglyceromutase → 2 molecules of 2-Phosphoglycerate (C3H7O7P)

STEP 9

The enzyme enolase removes a molecule of water from 2-phosphoglycerate to form phosphoenolpyruvate (PEP). This happens for each molecule of 2-phosphoglycerate.

2 molecules of 2-Phosphoglycerate (C3H7O7P) + enolase → 2 molecules of phosphoenolpyruvate (PEP) (C3H5O6P)

STEP 10

The enzyme pyruvate kinase transfers a P from PEP to ADP to form pyruvate and ATP. This happens for each molecule of phosphoenolpyruvate. This reaction yields 2 molecules of pyruvate and 2 ATP molecules.

2 molecules of phosphoenolpyruvate (C3H5O6P) + pyruvate kinase + 2 ADP → 2 molecules of pyruvate (C3H3O3-) + 2 ATP