Intracellular digestion is divided into heterophagic digestion and autophagic digestion.5 These two types take place in the lysosome and they both have very specific functions.6 Heterophagic intracellular digestion has an important job which is to break down all molecules that are brought into a cell by endocytosis.7 The degraded molecules need to be delivered to the cytoplasm; however, this will not be possible if the molecules are not hydrolyzed in the lysosome.8 Autophagic intracellular digestion is processed in the cell, which means it digests the internal molecules.9
Generally, autophagy includes three small branches, which are macroautophagy, microautophagy, and chaperone-mediated autophagy.10
Most organisms that use intracellular digestion belong to Kingdom Protista, such as amoeba and paramecium.
Amoeba
Amoeba uses pseudopodia to capture food for nutrition in a process called phagocytosis.
Paramecium
Paramecium uses cilia in the oral groove to bring food into the mouth pore which goes to the gullet. At the end of the gullet, a food vacuole forms. Undigested food is carried to the anal pore.
Euglena
Euglena is photosynthetic but also engulfs and digests microorganisms.
Anderson, O. Roger (1 January 1970). "Intracellular Digestion". The American Biology Teacher. 32 (8): 461–467. doi:10.2307/4443206. /wiki/Digital_object_identifier ↩
Roberts, M. B. V. Biology: A Functional Approach. Nelson Thornes. ISBN 9780174480198. /wiki/ISBN_(identifier) ↩
Jamieson, G. A.; Robinson, D. M. Mammalian Cell Membranes: Volume 2: The Diversity of Membranes. Elsevier. ISBN 9781483162782. /wiki/ISBN_(identifier) ↩
Glick, Danielle; Barth, Sandra; Macleod, Kay F. (2016-11-21). "Autophagy: cellular and molecular mechanisms". The Journal of Pathology. 221 (1): 3–12. doi:10.1002/path.2697. ISSN 0022-3417. PMC 2990190. PMID 20225336. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2990190 ↩