Give an account of Glycolysis. Where does it occur? What are the end products? Trace the fate of these products in both aerobic and anaerobic respiration.

(N/A) Definition: Glycolysis is the process of partial oxidation of glucose into two molecules of pyruvic acid.
Origin: The term glycolysis originates from the Greek words 'glycos' (sugar) and 'lysis' (splitting). The scheme was proposed by Gustav Embden,Otto Meyerhof,and $J$. Parnas,hence it is known as the $EMP$ pathway.
Location: Glycolysis occurs in the cytoplasm of the cell.
Process: In plants,glucose is derived from sucrose (end product of photosynthesis) or storage carbohydrates. Glucose and fructose are phosphorylated to form glucose-$6$-phosphate by the enzyme hexokinase. This is then isomerized to fructose-$6$-phosphate,which is further converted to fructose-$1,6$-bisphosphate using $ATP$. Fructose-$1,6$-bisphosphate splits into dihydroxyacetone phosphate $(DHAP)$ and $3$-phosphoglyceraldehyde $(PGAL)$. $PGAL$ is oxidized to $1,3$-bisphosphoglycerate,producing $NADH + H^+$. Subsequent steps involve the production of $ATP$ through substrate-level phosphorylation,ultimately yielding two molecules of pyruvic acid $(3C)$.
End Products: The primary end product is pyruvic acid. Other products include $2$ molecules of $ATP$ (net gain) and $2$ molecules of $NADH + H^+$.
Fate of Pyruvic Acid:
$1$. Lactic Acid Fermentation: Occurs in some bacteria and muscle cells under anaerobic conditions,converting pyruvate to lactic acid.
$2$. Alcoholic Fermentation: Occurs in yeast under anaerobic conditions,converting pyruvate to ethanol and $CO_2$.
$3$. Aerobic Respiration: In the presence of oxygen,pyruvic acid enters the mitochondria,undergoes oxidative decarboxylation to form Acetyl-$CoA$,and enters the Krebs cycle for complete oxidation into $CO_2$ and $H_2O$.