Editing Polysaccharide (section)

===Glycogen===
{{main|Glycogen}}

Glycogen serves as the secondary long-term energy storage in [[animal]] and [[fungi|fungal]] cells, with the primary energy stores being held in [[adipose tissue]]. Glycogen is made primarily by the [[liver]] and the [[muscle]]s, but can also be made by [[glycogenesis]] within the [[brain]] and [[stomach]].<ref>{{cite book | title = Anatomy and Physiology | vauthors = Saladin KS | publisher = McGraw-Hill | date = 2007 }}</ref>

Glycogen is analogous to [[starch]], a glucose polymer in [[plant]]s, and is sometimes referred to as ''animal starch'',<ref>{{cite encyclopedia | url=http://www.merriam-webster.com/medical/animal%20starch | title=Animal starch | dictionary=Merriam Webster | access-date=May 11, 2014}}</ref> having a similar structure to [[amylopectin]] but more extensively branched and compact than starch. Glycogen is a polymer of α(1→4) glycosidic bonds linked with α(1→6)-linked branches. Glycogen is found in the form of granules in the [[cytosol]]/cytoplasm in many [[cell (biology)|cell]] types and plays an important role in the [[glucose cycle]]. Glycogen forms an [[energy]] reserve that can be quickly mobilized to meet a sudden need for glucose, but one that is less compact and more immediately available as an energy reserve than  [[triglycerides]] (lipids).{{Citation needed|date=February 2021}}

In the liver [[hepatocyte]]s, glycogen can compose up to 8 percent (100–120&nbsp;grams in an adult) of the fresh weight soon after a meal.<ref name="Campbell 2006">{{cite book | vauthors = Campbell NA, Williamson B, Heyden RJ | title = Biology: Exploring Life | publisher = Pearson Prentice Hall | year = 2006 | location = Boston, Massachusetts | url = http://www.phschool.com/el_marketing.html | isbn = 978-0-13-250882-7 }}</ref> Only the glycogen stored in the liver can be made accessible to other organs. In the [[muscle]]s, glycogen is found in a low [[concentration]] of one to two percent of the muscle mass. The amount of glycogen stored in the body—especially within the [[muscles]], [[liver]], and [[red blood cells]]<ref>{{cite journal | vauthors = Moses SW, Bashan N, Gutman A | title = Glycogen metabolism in the normal red blood cell | journal = Blood | volume = 40 | issue = 6 | pages = 836–43 | date = December 1972 | pmid = 5083874 | doi = 10.1182/blood.V40.6.836.836 | url = http://www.bloodjournal.org/cgi/pmidlookup?view=long&pmid=5083874 | doi-access = free }}</ref><ref name="INGERMANN & VIRGIN, 1987">{{cite journal| vauthors = Ingermann RL, Virgin GL |title=Glycogen Content and Release of Glucose from Red blood cells of the Sipunculan Worm Themiste Dyscrita|url=http://jeb.biologists.org/cgi/reprint/129/1/141.pdf|journal=Journal of Experimental Biology|access-date=July 21, 2017|date=January 20, 1987|volume=129|issue=1 |pages=141–149|doi=10.1242/jeb.129.1.141|bibcode=1987JExpB.129..141I }}</ref><ref>{{cite journal | vauthors = Miwa I, Suzuki S | title = An improved quantitative assay of glycogen in erythrocytes | journal = Annals of Clinical Biochemistry | volume = 39 | issue = Pt 6 | pages = 612–3 | date = November 2002 | pmid = 12564847 | doi = 10.1258/000456302760413432 }}</ref>—varies with physical activity, [[basal metabolic rate]], and eating habits such as [[intermittent fasting]]. Small amounts of glycogen are found in the [[kidney]]s and even smaller amounts in certain [[glial]] cells in the [[brain]] and [[white blood cells]]. The [[uterus]] also stores glycogen during pregnancy to nourish the embryo.<ref name="Campbell 2006"/>

Glycogen is composed of a branched chain of glucose residues. It is primarily stored in the liver and muscles.<ref>{{Cite journal |last1=Ørtenblad |first1=N. |last2=Nielsen |first2=J. |date=2015 |title=Muscle glycogen and cell function – Location, location, location |url=https://onlinelibrary.wiley.com/doi/10.1111/sms.12599 |journal=Scandinavian Journal of Medicine & Science in Sports |language=en |volume=25 |issue=S4 |pages=34–40 |doi=10.1111/sms.12599 |issn=0905-7188}}</ref>
* It is an energy reserve for animals.
* It is the chief form of carbohydrate stored in animal organisms.
* It is insoluble in water. It turns brown-red when mixed with iodine.
* It also yields glucose on [[hydrolysis]].

<gallery mode="packed" heights="200px">
File:Glycogen structure.svg|Schematic 2-D cross-sectional view of glycogen. A core protein of [[glycogenin]] is surrounded by branches of [[glucose]] units. The entire globular granule may contain approximately 30,000 glucose units.<ref>{{cite book | url = https://books.google.com/books?id=SRptlOx7yj4C | page = 12 | title = Exercise physiology: energy, nutrition, and human performance | vauthors = McArdle WD, Katch FI, Katch VL | edition = 6th | publisher = Lippincott Williams & Wilkins | date = 2006 | isbn = 978-0-7817-4990-9 }}</ref>
File:Glycogen spacefilling model.jpg|A view of the [[atom]]ic structure of a single branched strand of [[glucose]] units in a glycogen [[molecule]].
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