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Cellulose inside plants is one of the examples of non-protein compounds that are using this term with the same purpose. Cellulose microfibrils are laid down in the inner surface of the primary cell wall. As the cell absorbs water, its volume increases and the existing microfibrils separate and new ones are formed to help increase cell strength.
Coextensive in the primary cell wall to both cellulose microfibrils and complementary glycan networks, is pectin which is a polysaccharide that contains many negatively charged galacturonic acid units. [17] Additionally, cellulose microfibrils also contribute to the shape of the plant via controlled-cell expansion.
It sometimes consists of three distinct layers - S 1, S 2 and S 3 - where the direction of the cellulose microfibrils differs between the layers. [1] The direction of the microfibrils is called microfibril angle (MFA). In the secondary cell wall of fibres of trees a low microfibril angle is found in the S2-layer, while S1 and S3-layers show a ...
However, the primary cell wall, can be defined as composed of cellulose microfibrils aligned at all angles. Cellulose microfibrils are produced at the plasma membrane by the cellulose synthase complex, which is proposed to be made of a hexameric rosette that contains three cellulose synthase catalytic subunits for each of the six units. [25]
Some animals, particularly ruminants and termites, can digest cellulose with the help of symbiotic micro-organisms that live in their guts, such as Trichonympha. In human nutrition, cellulose is a non-digestible constituent of insoluble dietary fiber, acting as a hydrophilic bulking agent for feces and potentially aiding in defecation.
Additionally, bacterial cellulose has a more crystalline structure compared to plant cellulose and forms characteristic ribbon-like microfibrils. [1] A hallmark of microbial cellulose, these thin microfibrils are significantly smaller than those in plant cellulose, making bacterial cellulose much more porous. [9] Three way branching point mechanism
Cellulose microfibrils are made on the surface of cell membranes to reinforce cells walls, which has been researched extensively by plant biochemists and cell biologist because 1) they regulate cellular morphogenesis and 2) they serve alongside many other constituents (i.e. lignin, hemicellulose, pectin) in the cell wall as a strong structural support and cell shape. [15]
The peritrophic matrix is composed of regularly arranged chitin microfibrils, (3–13% of matrix mass), and species specific proteins (20–55%) embedded in a proteoglycan matrix. [ 4 ] [ 5 ] The peritrophic matrix also includes very small pores which allow for passage of small molecules into and out of the matrix.