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Glycolysis is the first step in cellular respiration.
Cellular respiration is a process in which ATP, or adenosine triphosphate, is produced for the cell. ATP is an energy storage molecule that cells use.
In glycolysis, the main occurrence is that one glucose molecule is transformed into two molecules of pyruvate. Glycolysis is an anaerobic process, meaning it does not require oxygen to happen. You'll notice later stages of cellular respiration occur within the mitochondria; however, glycolysis occurs in the cytoplasm.
Glucose is a six-carbon sugar. When glucose enters the process of glycolysis, two ATPs will donate their phosphate groups to this glucose molecule. This donation of a phosphate from ATP is called phosphorylation.
The purpose of this is to transfer energy. ATPs are transferring their energy to the glucose molecule so that glycolysis can be carried out.
ATP stands for adenosine triphosphate; the prefix tri means three, so it has three phosphate groups attached to it. When an ATP gets rid of one of its phosphates, it becomes ADP; this stands for adenosine diphosphate, meaning it has two phosphates.
Next, the molecule is going to break down in half so that two three-carbon molecules are remaining with this phosphate group attached. Then the phosphates are going to be donated back to ATP. After it donates its phosphate, ATP becomes ADP. When it gains its phosphate back, it becomes ATP again.
Then you’re left with two three-carbon molecules; each of these is a molecule of pyruvate. Four molecules of ATP are being produced, but since ATP was used for the process to occur, there is only a net gain of two ATP.
Source: THIS WORK IS ADAPTED FROM SOPHIA AUTHOR AMANDA SODERLIND AND NATHAN LAMPSON