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Enzyme-catalyzed reactions: Glycolysis Cheat Sheet by

enzyme     catalyzed     reaction     glycolysis


Glycolysis (from glycose, an older term for glucose + -lysis degrad­ation) is the metabolic pathway that converts glucose C6H12O6, into pyruvate, CH3COCOO? + H+. The free energy released in this process is used to form the high-e­nergy compounds ATP (adenosine tripho­sphate) and NADH (reduced nicoti­namide adenine dinucl­eot­ide).

Glycolysis is a determined sequence of ten enzyme­-ca­talyzed reactions. The interm­ediates provide entry points to glycol­ysis. For example, most monosa­cch­arides, such as fructose and galactose, can be converted to one of these interm­edi­ates. The interm­ediates may also be directly useful. For example, the interm­ediate dihydr­oxy­acetone phosphate (DHAP) is a source of the glycerol that combines with fatty acids to form fat.
Note : there are ten enzymes in glycol­ysis, glucose is converted into 2 molecules of pyruvate, there are different reactions some are reversible and some are irreve­rsible. Use this paper:

Steps 1-5

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 (C6H11­O6P1)

Step 2: The enzyme phosph­ogl­uco­iso­merase converts glucose 6-phos­phate into its isomer fructose 6-phos­phate. Isomers have the same molecular formula, but the atoms of each molecule are arranged differ­ently.
Glucose 6-phos­phate (C6H11­O6P1) + Phosph­ogl­uco­iso­merase ? Fructose 6-phos­phate (C6H11­O6P1)

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 (C6H11­O6P1) + phosph­ofr­uct­okinase + ATP ? ADP + Fructose 1, 6-bisp­hos­phate (C6H10­O6P2)

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 (C6H10­O6P2) + aldolase ? Dihydr­oxy­acetone phosphate (C3H5O3P1) + Glycer­ald­ehyde phosphate (C3H5O3P1)

Step 5: The enzyme triose phosphate isomerase rapidly inter-­con­verts the molecules dihydr­oxy­acetone phosphate and glycer­ald­ehyde phosphate. Glycer­ald­ehyde phosphate is removed as soon as it is formed to be used in the next step of glycol­ysis.
Dihy­dro­xya­cetone phosphate (C3H5O3P1) ? Glycer­ald­ehyde phosphate (C3H5O­3P1)

Net result for steps 4 and 5:
Fructose 1, 6-bisp­hos­phate (C6H10­O6P2) ? 2 molecules of Glycer­ald­ehyde phosphate (C3H5O­3P1)


Steps 7-10

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 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 phosphate (C3H5O3P1) ? 2 molecules of 1,3-bi­sph­osp­hog­lyc­erate (C3H4O4P2)

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 (C3H4O4P2) + phosph­ogl­yce­rok­inase + 2 ADP ? 2 molecules of 3-phos­pho­gly­cerate (C3H5O4P1) + 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 (C3H5O4P1) + phosph­ogl­yce­rom­utase ? 2 molecules of 2-Phos­pho­gly­cerate (C3H5O­4P1)

Step 9: The enzyme enolase removes a molecule of water from 2-phos­pho­gly­cerate to form phosph­oen­olp­yruvic acid (PEP). This happens for each molecule of 2-phos­pho­gly­cerate.
2 molecules of 2-Phos­pho­gly­cerate (C3H5O4P1) + enolase ? 2 molecules of phosph­oen­olp­yruvic acid (PEP) (C3H3O3P1)

Step 10: The enzyme pyruvate kinase transfers a P from PEP to ADP to form pyruvic acid and ATP. This happens for each molecule of PEP. This reaction yields 2 molecules of pyruvic acid and 2 ATP molecules.
2 molecules of PEP (C3H3O3P1) + pyruvate kinase + 2 ADP ? 2 molecules of pyruvic acid (C3H4O3) + 2 ATP

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