Mesosomes are formed by invagination of plasma membranes. Respiratory enzymes occur over it. Mesosomes is equivalent to mitochondria and is called chondrioid. They help in respiration. Mesosomes are present in bacteria (prokaryotic organisms), yeast, Acetabularia and Chara are eukaryotic organism. They have mitochondria (power house of cell) for intra-cellular respiration.