Energy cannot be changed from one form into another without a loss of usable energy. When muscles convert chemical energy in ATP to mechanical energy, some is lost as heat. Energy conversions result in heat and therefore the entropy of the universe is always increasing. It takes a constant input of usable energy from the food you eat to keep you organized. Sum of all the biochemical pathways of a cell.
Exergonic reactions have a negative G and energy is released.
Occur when energy released by exergonic reaction is used to drive an endergonic reaction. ATP is a nucleotide made of base adenine, sugar ribose, and three phosphate groups. Metabolic energy is captured more easily if it is released in small increments. Each step in a series of chemical reactions is assisted by an enzyme. Enzymes are catalysts that speed chemical reactions without the enzyme being changed.