Biology, asked by irshad54, 1 year ago

what is glucolysis explain it's steps?

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Answered by shivam5566677pef3pn
1
hey mate here is your answer

Glycolysis is the metabolic process that serves as the foundation for both aerobic andanaerobic cellular respiration. In glycolysis, glucose is converted into pyruvate.


1. Hexokinase

Glucose enters the cell and is phosphorylated by the enzyme hexokinase, which transfers a phosphate group from ATP to sugar. The charge of the phosphate group traps the sugar in the cell because the plasma membrane is impermeable to ions. Phosphorylation also makes glucose more chemically reactive. In this diagram, the transfer of a phosphate group or pair of electrons from one reactant o another is indicated by coupled arrows. Part of the energy investment phase

2. Phosphoglucoisomerase

Glucose-6-phosphate is rearranged to convert it too its isomer, fructose-6-phosphate. Energy investment phase

3. Phosphofructokinase

This enzyme transfers a phosphate group from ATP to the sugar, investing another molecule of ATP in glycolysis. So far, 2 ATP have been used. With phosphate groups o its opposite ends, the sugar is now ready to be split in half. This is a key step for regulation of glycoysis; phosphofructokinase is allostericaly regulated by ATP and its products. Energy investment phase

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4. Aldolase

This is the reaction from which glycolysis gets its name. The enzyme cleaves the sugar molecule into two different three carbon sugars: dihydroxyacetone phosphate and glyceraldehyde 3 phosphate. These two sugars are isomers of each other. Energy investment phase

5. Isomerase

Isomerase catalyzes the reversible conversion between the two three carbon sugars. This reaction never reaches equilibrium in the cell because the enxt enxyme in glycolysis uses only glyceraldehyde-3-phosphate as its substrate (and not dihydroxyaceton phosphate). This pulls the equilibrium in the direction of glyceraldehyde-3-phosphate, which is removed as fast as it forms. Thus, the net result of steps 4 and 5 is cleavage of a six-carbon sugar into two molecules of glyceraldehyde-3-phosphate each will progress through the remaining steps of glycolysis. energy investment phase

6. Triose phosphate dehydrogenase

This enzyme catalyzes two sequential reactions whil it holds glyceraldehyde-3-phosphate in its active site. First, the sugar is oxidized by the transfer of electrons and H+ to NAD+, forming NADH ( a redox reaction). THis reaction is very exergonic, and the enzyme uses the released energy to attach a phosphate group to the oxidized substrate, making aproduct of very high potential energy. The source of the phosphates is the pool of inorganic phosphate ions that are always present in the cytosol. Notice that the coefficient 2 precedes all molecules in the energy payoff phase; these steps occur after glucose is split into two three-carbon sugars (step 4) Energy Payoff phase

Phosphoglycerokinase

Glycolysis produces some ATP by substrate-level phosphorylation. The phosphate group added in the previous step is transferred to ADP in an exergonic reaction. For each glucose molecule that began glycolysis, step 7 produces 2 ATP, since every product after the sugar splitting step (step 4) is doubled. Recall that 2 ATP were invested to get sugar ready for splitting; this ATP debt has now been repaid. Glucose has been converted to two molecules of 3-phosphoglycerate, which is not a sugar. The carbonyl group that characterizes a sugar has been oxidized to a carboxyl group ( -COO-), the hallmark of an organic acid. The sugar was oxidation has been used to make ATP. Energy Payoff phase

8. Phosphoglyceromutase

Next, this enzyme relocates the remaining phosphate group. This step prepares the substrate for the next reaction.

9. Enolase

This enzyme causes a double bond to form in the substrate by extracting a water molecule, yielding phosphoenolypyruvate (PEP). The electrons of the substrate are rearranged in such a way that the remaining phosphate bond becomes very unstable, preparing the substrate for the next reaction.

10. Pyruvate kinase

The last reaction of glycolysis produces more ATP by transferring the phosphate group from PEP to ADP, a second example of substrate level phosphorylation. Since this step occurs twice for each glucose molecule, 2 ATP are produced. Overall, glycolysis has used 2 ATP in the energy investment phase (steps 1 and 3) and produced 4 ATP in the energy payoff phase (steps 7 and 10), for a net gain of 2 ATP. Glcolysis has repaid the ATP investment with 100% interest. Additional energy was stored by step 6 in NADH, which can be used to make ATP by oxidative phosphorylation if oxygen is present. Glucose has been broken down and oxidized to the molecules of pyruvate, the end product of the glycolytic pathway. If oxygen is present, the chemical energy in pyruvate can be extracted by the citric acid cylce.

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