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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.
Cellulose is a polymer made with repeated glucose units bonded together by beta-linkages. Humans and many animals lack an enzyme to break the beta-linkages, so they do not digest cellulose. Certain animals, such as termites can digest cellulose, because bacteria possessing the enzyme are present in their gut. Cellulose is insoluble in water.
Cross-sectional view of the structures that can be formed by phospholipids in an aqueous solution. A biological membrane, biomembrane or cell membrane is a selectively permeable membrane that separates the interior of a cell from the external environment or creates intracellular compartments by serving as a boundary between one part of the cell and another.
Illustration of a eukaryotic cell membrane Comparison of a eukaryotic vs. a prokaryotic cell membrane. The cell membrane (also known as the plasma membrane or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of a cell from the outside environment (the extracellular space).
However, their ability to extract energy from cellulose digestion is less efficient than in ruminants. [2] Herbivores digest cellulose by microbial fermentation. Monogastric herbivores which can digest cellulose nearly as well as ruminants are called hindgut fermenters, while ruminants are called foregut fermenters. [3]
The main component of mucus is a glycoprotein called mucin and the type secreted varies according to the region involved. Mucin is viscous, clear, and clinging. Underlying the mucous membrane in the mouth is a thin layer of smooth muscle tissue and the loose connection to the membrane gives it its great elasticity. [5]
After synthesis, hemicelluloses are transported to the plasma membrane via Golgi vesicles. Each kind of hemicellulose is biosynthesized by specialized enzymes. [9] [10] Mannan chain backbones are synthesized by cellulose synthase-like protein family A (CSLA) and possibly enzymes in cellulose synthase-like protein family D (CSLD).
Biological membranes include cell membranes (outer coverings of cells or organelles that allow passage of certain constituents); [2] nuclear membranes, which cover a cell nucleus; and tissue membranes, such as mucosae and serosae. Synthetic membranes are made by humans for use in laboratories and industry (such as chemical plants).