Cell wall, algae

Agar occurs as a cell-wall constituent of the red marine algae Rho ophyceae, from which it is extracted by hot water, and marketed as a dry powder, flakes, or strips. It dissolves in hot water and sets on cooling to a jelly at a concentration as low as 0-5%. Its chief uses are as a solid medium for cultivating micro-organisms, as a thickener, emulsion stabilizer in the food industry and as a laxative. 

In general, many species of algae have cell walls resistant to digestive enzymes, dark colors, and bitter flavor. AH of these characteristics must be altered to make an acceptable food or feed product. 

Xylans as true homopolymers occur in seaweeds of the Palmariales and Nemaliales, however, their backbone consists of Xylp residues linked by -(1 3) (Type X3, Fig. la) or mixed -(1 3, 1 -> 4)-glycosidic linkages (Type Xmy Fig. lb). They are assumed mainly to have a structural function in the cell-wall architecture, but a reserve function cannot be ruled out [4]. From the microfibrils of green algae (Siphonales) such as Caulerpa and Bryop-sis sp., X3 was isolated and the structure confirmed by methylation analysis, C-NMR spectroscopy [7], as well as by mass spectrometry of enzymically released linear oligosaccharides up to a degree of polymerization (DP) of... 

Such a study has been performed on a model plant system, the Nitella flexilis cell wall [1, 2, 3]. This freshwater alga has giant intemodal cells whose easily isolated cell walls constitute a simplified model of higher plant cell walls it has no lignin and its pectin is not methylesterified. Isolated cell walls are cut in pieces and distributed in different lots over the whole exchange isotherm to reduce variability between experimental points. 

M Diatoms constitute a family of unicellular microscopic algae whose cell walls consist of two boxlike parts which contain silica. They are an important source of food for all kinds of marine organisms. 

This polysaccharide is the cell-wall material of siphoneous green algae. The unit cell is hexagonal, with a = c = 15.4 A (1.54 nm),... 

Diatoms are microscopic unicellular algae, with siliceous cell walls and the power of locomotion. 

Koivikko R, Loponen J, Honkanen T, Jormalainen V (2005) Contents of soluble, cell-wall-bound and exuded phlorotannins in the brown alga Fucus vesiculosus, with implications on their ecological functions. J Chem Ecol 31 195-212... 

In brown algae, phlorotannins are localized in specialized bodies called physodes (Ragan 1976). Shifting the experimental approach, from chemical assays of total phlorotannin concentration to microscopic methods that describe physode transport and establish the timeframes at which phlorotannins accumulate in response to abiotic or biotic stimuli, has provided new insight into the understanding of phlorotannin production and function. It is known that physodes are derived from the endoplasmic reticulum (ER) and Golgi of the cell (Schoenwaelder and Clayton 2000). It appears that physodes are transferred across the cytosol and incorporated into the cell wall, where the phlorotannins are assumed to have a structural role and thus be involved in primary metabolism (Schoenwaelder and Clayton 2000 Arnold and Targett 2003). 

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