All the phenomena of life growth, movement, irritability reproduction and others require the expenditure of energy (vīrya)[67] by the cells of organism. Living cells must have chemical energy. According to modern biology "All the living cells obtain biologically, useful energy primarily enzymic reactions in which electrons flow from one energy level to another.[68] The Jainācāryas state that vital force (paryāpti) by which organisms inhale the particles of suitable respiratory air, i.e. oxygen (ucchvāṣamarhamadya dalam) transforms it and exhales (as carbon-di-oxide) is called ucchvāṣaparyāpti.[69]
Now the question arises what is the necessity of paryāpti in respiration, when body and respiration are brought about by dehaucchvāṣnāma karmas (body respiration producing karma)? The reply is that the transformation of matters received by the soul as body is brought about by Śarīra Nāmakarma (body-producing karma), while the completion of the started aṅga (body) is brought about by paryāpti (vital force). [70] This difference of sarīranāma karma from paryāpti (performance) karma is due to the difference of Sādhya (performance). [71] Thus Ucchvāṣa-labdhi (faculty of energy of respiration i.e. prāṇa is brought about by śarīranāma karma (body producing karma) and its vyāparnam (manifestation or actually) takes place due to ucchvāṣa paryāpti (the vital force of respiration). [72]
Even there being the faculty (labdhi = energy = prāṇa) of respiration born of ucchvāṣanāmakarma, there should be ucchvāṣa paryāpti to make it manifested (i.e. bring it into actuality). [73] As for example, there being the śakti-capacity to cast the arrow, one does not become soldier, without the capacity of drawing the bow to make it a success. [74] This subtle reference to respiration and energy suggests that "for most organisms oxygen is the ultimate electron acceptor, oxygen reacts, with the electron and with hydrogen ions to form a molecule of water electrons are removed from a molecule of some food-stuff and transferred (by the action of specific enzyme) to some primary acceptor. [75]