This is an incorrect view. Both plants and animals carry on respiration as a major source of energy for vital functions. Only plants, however, are also capable of carrying out photosynthesis. The components of photosynthesis are sequestered within the chloroplast, whereas the major steps of respiration occur within the mitochondrion. Thus, both processes may be occurring simultaneously in any plant cell, since the compartmentalization of these functions precludes their interfering with each other. Many of the sequences in the pathways of respiration are found as part of the photosynthetic process; this suggests a close evolutionary association of the two processes. The balance between respiration and photosynthesis will determine whether there is a net uptake of O2 or CO2 from a particular plant region.
