All living things require an outside source of materials and energy. All of the chemical reactions that occur within a cell to provide these materials and energy are called:

a compound is a molecule made of atoms from different elements.

a. by the combination of an unlimited number of elements

a. energy is absorbed in the reaction.

if in a given reaction the energy of products is greater than the energy of reactants it means that reaction is endothermic and during the reaction, the energy is absorbed by reactants. in an endothermic reaction, the products have more stored chemical energy than the reactants. and in this reaction the reactants are more stable than products before the compounds with less energy are always more stable.