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Glycogen (black granules) in spermatozoa of a flatworm; transmission electron microscopy, scale: 0.3 μm. Glycogen is a multibranched polysaccharide of glucose that serves as a form of energy storage in animals, [2] fungi, and bacteria. [3] It is the main storage form of glucose in the human body.
Small amounts of glycogen are found in the kidneys 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. [17] Glycogen is composed of a branched chain of glucose residues. It is primarily stored in the liver and muscles. [21]
The peptidoglycan layer is substantially thicker in gram-positive bacteria (20 to 80 nanometers) than in gram-negative bacteria (7 to 8 nanometers). [4] Depending on pH growth conditions, the peptidoglycan forms around 40 to 90% of the cell wall 's dry weight of gram-positive bacteria but only around 10% of gram-negative strains.
EPSs are mostly composed of polysaccharides (exopolysaccharides) and proteins, but include other macromolecules such as DNA, lipids and humic substances. EPSs are the construction material of bacterial settlements and either remain attached to the cell's outer surface, or are secreted into its growth medium.
Chitin-glucan complex (CGC) is a copolymer (polysaccharide) that makes up fungal cell walls, consisting of covalently-bonded chitin and branched 1,3/1,6-ß-D-glucan. CGCs are alkaline-insoluble. Different species of fungi have different structural compositions of chitin and β-glucan making up the CGCs in their cell walls. [1]
The capsule is found most commonly among gram-negative bacteria: Escherichia coli (in some strains) Neisseria meningitidis [9] [10] [11] Klebsiella pneumoniae [12] [13] [14] Haemophilus influenzae [15] Pseudomonas aeruginosa [16] Salmonella [17] Acinetobacter baumannii [18] [19] However, some gram-positive bacteria may also have a capsule:
Cellulose is an example of a (1→4)-β-D-glucan composed of glucose units. Beta-glucans, β-glucans comprise a group of β-D-glucose polysaccharides naturally occurring in the cell walls of cereals, bacteria, and fungi, with significantly differing physicochemical properties dependent on source.
Aspergillus species are highly aerobic and are found in almost all oxygen-rich environments, where they commonly grow as molds on the surface of a substrate, as a result of the high oxygen tension. Commonly, fungi grow on carbon-rich substrates like monosaccharides (such as glucose) and polysaccharides (such as amylose).