What is the Main Transformation That Occurs During Glycolysis

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18.3A: Glycolysis

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Learning Objectives

Briefly describethe function of glycolysis during aerobic respiration and indicate the reactants and products.
State whether or not glycolysis requires oxygen.
Compare where glycolysis occurs in prokaryotic cells and in eukaryotic cells.
Land whether steps ane and 3 of glycolysis are exergonic or endergonic and point why.
State why one molecule of glucose is able to produce two molecules of pyruvate during glycolysis.
Define substrate-level phosphorylation.
State the full number and the net number of ATP produced past substrate-level phosphorylation during glycolysis.
During aerobic respiration, country what happens to the 2 NADH produced during glycolysis.
During aerobic respiration, state what happens to the 2 molecules of pyruvate produced during glycolysis.

Glycolysis is a partial breakdown of a six-carbon glucose molecule into two, iii-carbon molecules of pyruvate, 2NADH +2H⁺, and 2 net ATP as a result of substrate-level phosphorylation, every bit shown in (Figures 1 and ii).

Figure \(\PageIndex{1}\) and 2: A Summary of Glycolysis

Steps of Glycolysis

A phosphate from the hydrolysis of a molecule of ATP is added to glucose, a 6-carbon saccharide, to form glucose half dozen-phosphate.
The glucose 6-phosphate molecule is rearranged into an isomer called fructose 6-phosphate.
A second phosphate provided past the hydrolysis of a second molecule of ATP is added to the fructose six-phosphate to class fructose 1,
The 6-carbon fructose i,6-biphosphate is divide into two molecules of glyceraldehyde 3-phosphate, a 3-carbon molecule.
Oxidation and phosphorylation of each glyceraldehyde 3-phosphate produces one,3-biphosphoglycerate with a loftier-free energy phosphate bond (wavy ruby line) and NADH.
Through substrate-level phosphorylation, the high-energy phosphate is removed from each one,3-biphosphoglycerate and transferred to ADP forming ATP and 3-phosphoglycerate.
Each 3-phosphoglycerate is oxidized to form a molecule of phosphoenolpyruvate with a high-free energy phosphate bond.
Through substrate-level phosphorylation, the high-energy phosphate is removed from each phosphoenolpyruvate and transferred to ADP forming ATP and pyruvate.

In summary, one molecule of glucose produces two internet ATPs (two ATPs were used at the beginning; four ATPs were produced through substrate-level phosphorylation), two molecules of NADH + 2H⁺, and two molecules of pyruvate.

Glycolysis
occurs in the

cytoplasm

of the cell. The overall reaction is:

\[glucose (6C) + two NAD+ two ADP + 2 inorganic phosphates (P_i)\]

\[ \rightarrow 2 pyruvate (3C) + 2 NADH + 2 H^+ + two ATP\]

Glycolysis as well produces a number of central precursor metabolites, as shown in Effigy \(\PageIndex{3}\). Glycolysis does not require oxygen and tin occur nether aerobic and anaerobic weather. However, during aerobic respiration, the two reduced NADH molecules transfer protons and electrons to the electron ship chain to generate boosted ATPs by way of oxidative phosphorylation.

alt — Figure \(\PageIndex{iii}\): Integration of Metabolism – Precursor Metabolites.Carbohydrates, proteins, and lipids can be used as energy sources; metabolites involved in energy production can be used to synthesize carbohydrates, proteins, lipids, nucleic acids, and cellular structures.

The glycolysis pathway involves 9 singled-out steps, each catalyzed by a unique enzyme. Yous are not responsible for knowing the chemic structures or enzymes involved in the steps below. They are included to help illustrate how the molecules in the pathway are manipulated past the enzymes in order to to achieve the required products.

Stride i

To initiate glycolysis in eukaryotic cells (Figure \(\PageIndex{4}\)), a molecule of ATP is hydrolyzed to transfer a phosphate group to the number 6 carbon of glucose to produce glucose 6-phosphate. In prokaryotes, the conversion of phosphoenolpyruvate (PEP) to pyruvate provides the energy to send glucose across the cytoplasmic membrane and, in the process, adds a phosphate group to glucose producing glucose 6-phosphate.

alt — Figure \(\PageIndex{4}\): Glycolysis, Step 1. To initiate glycolysis in eukaryotic cells, shown in this figure, a molecule of ATP is hydrolyzed to transfer a phosphate group to the number 6 carbon of glucose to produce glucose 6-phosphate. In prokaryotes, the conversion of phosphoenolpyruvate (PEP) to pyruvate provides the free energy to send glucose beyond the cytoplasmic membrane and, in the process, adds a phosphate grouping to glucose producing glucose 6-phosphate.

Step 2

The glucose 6-phosphate is rearranged to an isomeric form called fructose 6-phosphate (Figure \(\PageIndex{v}\)).

alt — Figure \(\PageIndex{5}\): Glycolysis, Step 2. The glucose vi-phosphate is rearranged to an isomeric form chosen fructose 6-phosphate.

Step iii

A second molecule of ATP is hydrolyzed to transfer a phosphate grouping to the number 1 carbon of fructose half dozen-phosphate to produce fructose 1,six-biphosphate (Figure \(\PageIndex{6}\)).

alt — Figure \(\PageIndex{6}\): Glycolysis, Pace three. A second molecule of ATP is hydrolyzed to transfer a phosphate group to the number ane carbon of fructose vi-phosphate to produce fructose 1,6-biphosphate.

Step 4

The 6-carbon fructose 1,vi biphosphate is split to form ii, 3-carbon molecules: glyceraldehyde three-phosphate and dihydroxyacetone phosphate. The dihydroxyacetone phosphate is and so converted into a 2d molecule of glyceraldehyde iii-phosphate (Figure \(\PageIndex{seven}\)). 2 molecules of glyceraldehyde 3-phosphate will now become through each of the remaining steps in glycolysis producing two molecules of each product.

alt — Effigy \(\PageIndex{vii}\): Glycolysis, Footstep iv. The 6-carbon fructose 1,vi biphosphate is separate to class two, 3-carbon molecules: glyceraldehyde 3-phosphate and dihydroxyacetone phosphate. The dihydroxyacetone phosphate is then converted into a 2nd molecule of glyceraldehyde 3-phosphate. Two molecules of glyceraldehyde three-phosphate will now go through each of the remaining steps in glycolysis producing two molecules of each production.

Step 5

As each of the two molecules of glyceraldehyde 3-phosphate are oxidized, the energy released is used to add an inorganic phosphate group to course two molecules of i,iii-biphosphoglycerate, each containing a loftier-energy phosphate bond. During these oxidations, two molecules of NAD⁺
are reduced to form 2NADH + 2H⁺
(Effigy \(\PageIndex{8}\)). During aerobic respiration, the 2NADH + 2H⁺
carry protons and electrons to the electron transport chain to generate additional ATP by oxidative phosphorylation.

alt — Figure \(\PageIndex{viii}\): Glycolysis, Step 5. Equally each of the two molecules of glyceraldehyde 3-phosphate are oxidized, the energy released is used to add an inorganic phosphate group to form two molecules of 1,iii-biphosphoglycerate, each containing a loftier-energy phosphate bail. During these oxidations, two molecules of NAD⁺
are reduced to form 2 NADH + 2H⁺.

Footstep 6

As each of the 2 molecules of ane,3-biphosphoglycerate are converted to 3-phosphoglycerate, the high-energy phosphate group is added to ADP producing 2 ATP past substrate-level phosphorylation, a shown in Figure \(\PageIndex{9}\).

alt — Figure \(\PageIndex{9}\): Glycolysis, Step 6. As each of the two molecules of 1,three-biphosphoglycerate are converted to 3-phosphoglycerate, the high-energy phosphate group is added to ADP producing 2 ATP past substrate-level phosphorylation.

Step vii

The two molecules of iii-phosphoglycerate are rearranged to form two molecules of two-phosphoglycerate (Figure \(\PageIndex{10}\)).

alt — Figure \(\PageIndex{x}\): Glycolysis, Step seven. The two molecules of three-phosphoglycerate are rearranged to form two molecules of 2-phosphoglycerate.

Step 8

Water is removed from each of the ii molecules of ii-phosphoglycerate converting the phosphate bonds to a high-energy phosphate bonds as 2 molecules of phosphoenolpyruvate are produced (Figure \(\PageIndex{eleven}\)).

alt — Figure \(\PageIndex{11}\): Glycolysis, Footstep 8. H2o is removed from each of the two molecules of two-phosphoglycerate converting the phosphate bonds to a high-energy phosphate bonds equally ii molecules of phosphoenolpyruvate are produced.

Step nine

As the two molecules of phosphoenolpyruvate are converted to two molecules of pyruvate, the high-energy phosphate groups are added to ADP producing 2 ATP by substrate-level phosphorylation, a shown in Figure \(\PageIndex{12}\).

alt — Figure \(\PageIndex{12}\): Glycolysis, Step nine. Equally the ii molecules of phosphoenolpyruvate are converted to 2 molecules of pyruvate, the high-energy phosphate groups are added to ADP producing 2 ATP by substrate-level phosphorylation.

Through an intermediate step called the transition reaction, the 2 molecules of pyruvate so enter the citric acid cycle to exist further broken downward and generate more ATPs by oxidative phosphorylation.

Overview

Glycolysis is a partial breakup of a six-carbon glucose molecule into two, iii-carbon molecules of pyruvate, 2NADH +2H⁺, and two net ATP as a result of substrate-level phosphorylation. Glycolysis occurs in the cytoplasm of the prison cell.

The overall Glycolysis reaction is:

glucose (6C) + 2 NAD⁺
2 ADP +2 inorganic phosphates (P_i)

yields 2 pyruvate (3C) + 2 NADH + 2 H⁺
+ 2 internet ATP

Exterior Links

YouTube moving-picture show of Glycolysis: Overview Reaction for Cellular Respiration
YouTube movie: How Glycolysis Works

Summary

Aerobic respiration is the aerobic catabolism of nutrients to carbon dioxide, water, and energy, and involves an electron send system in which molecular oxygen is the final electron acceptor.
Aerobic respiration involves four stages: glycolysis, a transition reaction that forms acetyl coenzyme A, the citric acid (Krebs) cycle, and an electron send chain and chemiosmosis.
Glycolysis is a partial breakdown of a six-carbon glucose molecule into ii, three-carbon molecules of pyruvate, 2NADH +2H⁺, and 2 internet ATP equally a result of substrate-level phosphorylation.
The overall reaction for glycolysis is: glucose (6C) + 2 NAD⁺
2 ADP +2 inorganic phosphates (P_i) yields ii pyruvate (3C) + 2 NADH + ii H⁺
+ two net ATP.
Glycolysis does not require oxygen and can occur nether aerobic and anaerobic atmospheric condition. However, during aerobic respiration, the 2 reduced NADH molecules transfer protons and electrons to the electron transport chain to generate additional ATPs by manner of oxidative phosphorylation.
Glycolysis besides produces a number of fundamental forerunner metabolites.
Through an intermediate step called the transition reaction, the two molecules of pyruvate then enter the citric acid wheel to be further cleaved down and generate more ATPs by oxidative phosphorylation.