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It is a primary component of cell walls in fungi (especially filamentous and mushroom-forming fungi), the exoskeletons of arthropods such as crustaceans and insects, the radulae, cephalopod beaks and gladii of molluscs and in some nematodes and diatoms. [2] [3] It is also synthesised by at least some fish and lissamphibians. [4]
The fungal cell wall is made of a chitin-glucan complex; while glucans are also found in plants and chitin in the exoskeleton of arthropods, [36] fungi are the only organisms that combine these two structural molecules in their cell wall. Unlike those of plants and oomycetes, fungal cell walls do not contain cellulose. [37] [38]
Unlike fungi, oomycetes typically possess cell walls of cellulose and glucans rather than chitin, although some genera (such as Achlya and Saprolegnia) do have chitin in their walls. [34] The fraction of cellulose in the walls is no more than 4 to 20%, far less than the fraction of glucans. [34]
In plant cell walls, cellulose and hemicellulose is embedded in a pectin scaffold [29] that requires pectin degrading enzymes, such as polygalacturonases and pectin lyases to weaken the plant cell wall and uncover hemicellulose and cellulose to further enzymatic degradation. [30]
During tip growth, cell walls are extended by the external assembly and polymerization of cell wall components, and the internal production of new cell membrane. [3] The Spitzenkörper is an intracellular organelle associated with tip growth. It is composed of an aggregation of membrane-bound vesicles containing cell wall components.
Typical fungal cell wall structure. Zygomycetes exhibit a special structure of cell wall. Most fungi have chitin as structural polysaccharide, while zygomycetes synthesize chitosan, the deacetylated homopolymer of chitin. Chitin is built of β-1,4 bonded N-acetyl glucosamine. Fungal hyphae grow at the tip.
The process leading to frog mortality is thought to be the loss of essential ions through pores made in the epidermal cells by the chytrid during its replication. [ 29 ] Recent research has revealed that elevating salt levels slightly may be able to cure chytridiomycosis in some Australian frog species, [ 30 ] although further experimentation ...
This relationship is supported by a number of observed differences between the characteristics of oomycetes and fungi. For instance, the cell walls of oomycetes are composed of cellulose rather than chitin [12] and generally do not have septations. Also, in the vegetative state they have diploid nuclei, whereas fungi have haploid nuclei.