Describe the phase until the formation of two molecules of pyruvic acid from glucose takes place.

(N/A) Definition: Glycolysis is the metabolic pathway that describes the phase until the formation of two molecules of pyruvic acid from one molecule of glucose.
Origin: The term glycolysis originates from the Greek words 'glycos' (sugar) and 'lysis' (splitting).
The scheme of glycolysis was proposed by Gustav Embden,Otto Meyerhof,and $J$. Parnas,and is often referred to as the $EMP$ pathway.
In anaerobic organisms,only glycolysis occurs. Glycolysis takes place in the cytoplasm of the cell,where glucose undergoes partial oxidation to form two molecules of pyruvic acid.
In plants,glucose is derived from sucrose,which is the end product of photosynthesis,or from storage carbohydrates. Both glucose and fructose enter the glycolytic pathway readily.
Glucose and fructose are phosphorylated to form Glucose-$6$-phosphate by the enzyme hexokinase.
Glucose $+$ $ATP$ $\xrightarrow{\text{Hexokinase}}$ Glucose-$6$-Phosphate
This phosphorylated glucose isomerizes to produce Fructose-$6$-phosphate.
Glucose-$6$-Phosphate $\rightleftharpoons$ Fructose-$6$-Phosphate
Subsequent steps for glucose and fructose metabolism are identical.
Glycolysis involves a chain of ten enzyme-controlled reactions to produce pyruvate from glucose.
Fructose-$6$-phosphate is converted into Fructose-$1,6$-bisphosphate in the presence of $ATP$.
$ATP$ is utilized at two steps: first,in the conversion of glucose to Glucose-$6$-phosphate,and second,in the conversion of Fructose-$6$-phosphate to Fructose-$1,6$-bisphosphate.
Fructose-$1,6$-bisphosphate is then split into Dihydroxyacetone phosphate $(DHAP)$ and $3$-phosphoglyceraldehyde $(PGAL)$.
Fructose-$1,6$-bisphosphate $\rightleftharpoons$ $DHAP$ $(3C)$ $+$ $PGAL$ $(3C)$
In one step,$NAD^+$ is reduced to $NADH + H^+$ when $3$-phosphoglyceraldehyde is converted to $1,3$-bisphosphoglycerate $(BPGA)$.
$3$-phosphoglyceraldehyde $+$ $NAD^+$ $+$ $Pi$ $\longrightarrow$ $1,3$-bisphosphoglycerate $+$ $NADH + H^+$
Two redox-equivalents are removed from $PGAL$ and transferred to $NAD^+$. $PGAL$ is oxidized and combined with inorganic phosphate to form $BPGA$.
The conversion of $BPGA$ to $3$-phosphoglyceric acid $(PGA)$ is an energy-yielding process,where energy is trapped by the formation of $ATP$.
Another $ATP$ is synthesized during the conversion of Phosphoenolpyruvate $(PEP)$ to pyruvic acid.
Pyruvic acid is the key product of glycolysis. Its metabolic fate depends on cellular needs,typically following one of three pathways: $(1)$ Lactic acid fermentation,$(2)$ Alcoholic fermentation,or $(3)$ Aerobic respiration.