Cellulose
From Proteopedia
(Difference between revisions)
| Line 6: | Line 6: | ||
Glucose, the building block of cellulose and starch, can form six-membered rings with two distinct anomers, alpha or beta. These forms differ in the stereochemistry of the anomeric carbon C1 (<jmol><jmolLink><script> select 823.C1; selectionHalos ON; delay 0.5;selectionHalos OFF;</script><text>☼</text></jmolLink> </jmol>). Cellobiose (reload <scene name='82/824000/Cellobiose/1'>initial scene</scene>) is a breakdown product of cellulose which shows the beta 1,4 linkage also present in cellulose. In contrast, starch can be broken down to maltose, a stereoisomer of cellobiose showing an alpha 1,4 linkage. Thus, it is the type of glycosidic linkage that distinguishes cellulose from starch at the molecular level. | Glucose, the building block of cellulose and starch, can form six-membered rings with two distinct anomers, alpha or beta. These forms differ in the stereochemistry of the anomeric carbon C1 (<jmol><jmolLink><script> select 823.C1; selectionHalos ON; delay 0.5;selectionHalos OFF;</script><text>☼</text></jmolLink> </jmol>). Cellobiose (reload <scene name='82/824000/Cellobiose/1'>initial scene</scene>) is a breakdown product of cellulose which shows the beta 1,4 linkage also present in cellulose. In contrast, starch can be broken down to maltose, a stereoisomer of cellobiose showing an alpha 1,4 linkage. Thus, it is the type of glycosidic linkage that distinguishes cellulose from starch at the molecular level. | ||
| - | Longer chains of beta 1,4 linked glucoses are found in cellulose. When cellulose is synthesized, these chains are made individually (like seen during <scene name='82/824000/Cellulose/2'>biosynthesis</scene>). Again, the linkages are all of the beta 1,4 type (<jmol><jmolLink><script> select *.C1; selectionHalos ON; delay 0.5;selectionHalos OFF;</script><text>☼</text></jmolLink> </jmol | + | Longer chains of beta 1,4 linked glucoses are found in cellulose. When cellulose is synthesized, these chains are made individually (like seen during <scene name='82/824000/Cellulose/2'>biosynthesis</scene>). Again, the linkages are all of the beta 1,4 type (<jmol><jmolLink><script> select *.C1; selectionHalos ON; delay 0.5;selectionHalos OFF;</script><text>☼</text></jmolLink> </jmol>). In this structure, the polymer chain is elongated inside the cell and secreted through the membrane, surrounded by the <scene name='82/824000/Cellulose/3'>enzyme</scene> throughout. |
| - | Once secreted, individual cellulose chains aggregate to from semi-crystalline cellulose microfibrils. There are multiple forms of cellulose (I alpha and beta, II, III) which differ in the orientation and the detailed interactions between linear polymers. A model of a cellulose type I beta | + | Once secreted, individual cellulose chains aggregate to from semi-crystalline cellulose microfibrils. There are multiple forms of cellulose (I alpha and beta, II, III) which differ in the orientation and the detailed interactions between linear polymers. A <scene name='82/824000/Contacts/1'>model of a cellulose type I beta microfibril</scene> shows how inter-chain hydrogen bonding and hydrophobic interactions lead to a highly ordered structure. The model was made using cellulose builder (http://cces-sw.iqm.unicamp.br/cces/admin/cellulose, <ref>PMID:10932243</ref>) and is based on a fiber-diffraction study by Nishiyama et al <ref>DOI:10.1021/ja0257319</ref>. |
Revision as of 09:52, 24 August 2019
Cellulose is the most abundant biopolymer on earth. It occurs in plant cell walls and in bacteria. Common materials containing high amounts of cellulose are wood, paper, and cotton. Cellulose is a water-insoluble polysaccharide that humans can not digest. It is a linear polymer of beta-1,4 linked glucose building blocks, with chains arranged in microfibrils held together by hydrogen bonds and hydrophobic interactions. Cellulose is related to but distinct from starch, a water-soluble carbohydrate digestible by humans containing alpha-1,4 linked glucose building blocks.
Structure
| |||||||||||
References
- ↑ Richardson JS. Early ribbon drawings of proteins. Nat Struct Biol. 2000 Aug;7(8):624-5. doi: 10.1038/77912. PMID:10932243 doi:http://dx.doi.org/10.1038/77912
- ↑ Nishiyama Y, Langan P, Chanzy H. Crystal structure and hydrogen-bonding system in cellulose Ibeta from synchrotron X-ray and neutron fiber diffraction. J Am Chem Soc. 2002 Aug 7;124(31):9074-82. doi: 10.1021/ja0257319. PMID:12149011 doi:http://dx.doi.org/10.1021/ja0257319
