Storage Granules- Definition, Structure, Functions and Diagram

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Storage Granules Definition

  • Storage granules are membrane-bounded vesicles containing condensed materials.
  • They are also known as zymogen granules or condensing vacuoles.
  • Storage granules are an important component of metabolism in many organisms spanning the bacterial, eukaryotes and archaeal domains.
  • These granules are the parts of the cell that store the cell’s energy reserves as well as other important metabolites.

Storage Granules

Figure: Diagram of Storage Granules. Image Source: Slide Player

Structure of Storage Granules

  • Storage granules are simple small organelles, bounded by a lipid bilayer membrane. On the inside of the membrane, it contains the stored material.
  • Different materials may be stored for different purposes by storage granules depending upon the location where they are found. For example, mast‐cell storage granules contain histamine, while those of pancreatic B cells contain insulin.
  • Generally, storage granules are polyphosphate bodies that contain a large amount of phosphorous and oxygen. They also have increased levels of iron and magnesium.
  • Primary lysosomes which are also called storage granules are newly formed organelles bounded by a single membrane and typically having a diameter of 100 nm. They contain the degradative enzymes which have not participated in any digestive process.

Functions of Storage Granules

  • Granules found in plastids or in the cytoplasm, assumed to be food reserves, often of glycogen or other carbohydrate polymers.
  • In prokaryotes, nutrients and reserves may be stored in the cytoplasm in the form of glycogen, lipids, polyphosphate, or in some cases, sulfur or nitrogen.
  • Sulfur granules are especially common in bacteria that use hydrogen sulfide as an electron source.
  • The lysosomes of plant cells are membrane-bounded storage granules containing hydrolytic digestive enzymes, e.g., large vacuoles of parenchymatous cells of corn seedlings, protein or aleurone bodies and starch granules of cereal and other seeds.

References

  1. Verma, P. S., & Agrawal, V. K. (2006). Cell Biology, Genetics, Molecular Biology, Evolution & Ecology (1 ed.). S .Chand and company Ltd.
  2. Alberts, B. (2004). Essential cell biology. New York, NY: Garland Science Pub.
  3. https://www.biology-online.org/dictionary/Storage_granule
  4. https://onlinelibrary.wiley.com/doi/pdf/10.1002/jemt.1070320209
  5. https://www.cellsalive.com/cells/bactcell.htm
  6. Toso, D. B., Henstra, A. M., Gunsalus, R. P., & Zhou, Z. H. (2011). Structural, mass and elemental analyses of storage granules in methanogenic archaeal cells. Environmental microbiology, 13(9), 2587-99.
  7. http://www.oxfordreference.com/view/10.1093/oi/authority.20110803100535190
  8. https://bio.libretexts.org/TextMaps/Microbiology/Book%3A_Microbiology_(Boundless)/4%3A_Cell_Structure_of_Bacteria%2C_Archaea%2C_and_Eukaryotes/4.6%3A_Specialized_Internal_Structures_of_Prokaryotes/4.6B%3A_Cell_Inclusions_and_Storage_Granules
  9. https://www.reference.com/science/storage-granules-important-cell-97c6939fc28e88f1

Storage Granules- Definition, Structure, Functions and Diagram

About Author

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Sagar Aryal, PhD

Dr. Sagar Aryal is a microbiologist, researcher, and science communicator from Nepal. He is also co-founder and Research Head of the Department of Natural Products at the Kathmandu Research Institute for Biological Sciences (KRIBS), where he leads research on natural product discovery and microbial biodiversity. Dr. Aryal earned his Ph.D. in Microbiology from Tribhuvan University, Kathmandu, Nepal, in 2025, supported by a DAAD Research Grant and a University Grants Commission (UGC) Nepal Ph.D. Fellowship. His research interests include Actinomycetes, Myxobacteria, microbial taxonomy, and natural products, particularly the discovery of bioactive compounds with potential pharmaceutical applications. He isolated and identified Nocardia nepalensis, a novel bacterial species from Nepal, contributing to understanding microbial diversity in the region. Dr. Aryal has published more than 16 research articles in international journals and contributed three book chapters to established academic publications. He has presented scientific research findings and developed international research collaborations through visits to more than 18 countries across Asia, Europe, North America, and Oceania. From 2023 to 2025, he served as the American Society for Microbiology (ASM) Young Ambassador to Nepal. Since December 2025, he has served as an Editorial Board Member of Scientific Reports, a Nature Portfolio journal. In recognition of his scientific contributions, Dr. Aryal received the NAST Science and Technology Youth Award 2025 from the Nepal Academy of Science and Technology. He previously received the Frs. Locke and Stiller Research Award (LSRA) for the 2017-2018 cycle from St. Xavier's College, Kathmandu, and a Nepal Academy of Science and Technology (NAST) Research Grant for 2017-2018. Alongside his scientific career, Dr. Aryal has more than 15 years of experience in blogging, content writing, and search engine optimization (SEO).