Question

give reason that Internal respiration liberates energy.

Answer 1

Cellular respiration is the process by which food molecules react with oxygen and are broken down to carbon dioxide and water with a net gain of captured energy in the form of ATP molecules. Therefore, it is the conversion of chemical energy of ORGANIC molecules to metabolically usable energy within living cells. Most of the process occurs within MITOCHONDRIA in Eukaryotic cells. All organisms utilize the processes of cellular respiration to provide energy for cellular maintenance and for the production of starting materials for the biosynthesis of needed compounds.

Cellular respiration occurs  through out the day in all organisms. Respiration is sometimes called BIOLOGICAL OXIDATION and thus may be compared to burning. Although both are OXIDATION reactions, the manner in which the energy is released differs in the two processes. In both, the energy released is obtained from chemical bonds. (CO2)  may be a WASTE PRODUCT in both.  In burning there is an uncontrolled, rapid release of energy with accompanying  high temperatures but in CELLULAR RESPIRATION energy is released in discrete amounts due to  enzymatic control  of the process.

 Cellular respiration is a series of ENZYMATIC REACTIONS, and biological combustion cannot take place any faster than the controlling enzymes will permit. In cellular respiration most of the energy is used to create NEW CHEMICAL BONDS and only a relatively small amount of heat energy is liberated (2nd Law of Thermodynamics).

Biological oxidation is not necessarily the direct action of oxygen on a substance. It may mean the removal of some electrons resulting in the formation of HYDROGEN IONS (H+) which are passed along an assembly line of CARRIER MOLECULES. When the hydrogen ions and the electrons reach oxygen, they combine with it to form water.The energy released by oxidations is not transformed into heat but into a form that can be used by the cells. Transformation consists of making energy-rich compounds of ADENOSINE TRIPHOSPHATE or ATP. Most of the energy required by the cell is provided in this way and most of it is found in the mitochondria. Some of the energy of ATP is used in the mitochondria but most of the ATP is immediately transferred to the cytoplasm to power the other activities of the cell.