(N/A) $\rightarrow$ Metabolic pathways lead to a more complex structure from a simpler structure (e.g.,acetic acid is converted into cholesterol) or simpler substances from a complex structure (e.g.,glucose is converted into lactic acid in our skeletal muscle).
$\rightarrow$ The first type of reactions are called anabolic pathways. The latter constitute catabolic pathways.
$\rightarrow$ Anabolic pathways consume energy; for example,the formation of protein from amino acids requires energy input. Catabolic pathways lead to the release of energy; for example,when glucose is converted to lactic acid in our skeletal muscle,energy is liberated.
$\rightarrow$ The metabolic pathway from glucose to lactic acid occurs in $10$ metabolic steps and is called glycolysis.
$\rightarrow$ Living organisms trap this energy liberated during degradation and store it in the form of chemical bonds.
$\rightarrow$ As and when required,this bond energy is utilized for biosynthetic,osmotic,and mechanical work performed by organisms.
$\rightarrow$ The most important form of energy currency in living systems is the bond energy in the form of $ATP$ (Adenosine Triphosphate).