VCAC: Cellular Processes: Glycolysis - The Reactions: Advanced Look: Energy Consumption

The first five stages of glycolysis are known as the Energy Consumption Phase, because ATP is consumed during the first half of the pathway. Clicking on each of the thumbnail images will bring up a larger, labeled version of the described scene.

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	Glycolysis oxidizes one molecule of glucose into two molecules of pyruvate.
	The first step of glycolysis involves a kinase enzyme and begins with glucose and ATP as substrates.
	Step one produces one molecule of ADP and one molecule of glucose 6-phosphate. This step is irreversible.
	Step two is catalyzed by an isomerase enzyme and the required substrate is glucose 6-phosphate.
	The isomerase at step two rearranges the glucose 6-phosphate molecule into fructose 6-phosphate.
	Step three involves another kinase enzyme and requires fructose 6-phosphate and ATP as substrates.
	ATP is consumed again at step 3, producing ADP and fuctose 1,6-bisphosphate. Like step one, this step is also irreversible.
	Step four is catalyzed by a lyase enzyme and requires fructose 1,6-bisphosphate as the substrate.
	The lyase enzyme splits the fructose 1,6-bisphosphate into glyceraldehyde 3-phosphate, and dihydroxyacetone phosphate.
	Step five involves another isomerase enzyme. Only the dihydroxyacetone phosphate is a substrate for this step.
	The isomerase enzyme converts the dihydroxyacetone phosphate into a second glyceraldehyde 3-phosphate molecule.
	The first half of glycolysis results glucose being converted into two glyceraldehyde 3-phosphate molecules and the consumption of two ATP molecules.

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