Carbohydrate invertebrates

An inventory of known biomacromolecules is provided in Table 22.3. Many of these play essential metabolic roles in enabling growth and reproduction, such as the carbohydrates, lipids, proteins, and polynucleotides. Others are components of cell walls and exoskeletons. Some organisms, such as bacteria, plankton, plants, and lower invertebrates, synthesize biomolecules, called secondary metabolites, that are used to control ecological relationships, including predator/prey, host/symbiont, mating/spawning, and competition for food or space. 

Ferritin iron cores, or polynuclear iron complexes in lipid vesicles or in matrices of protein and complex carbohydrates, appear to be the precursors of minerals such as hematite and magnetite that form in certain bacteria (31), marine Invertebrates (22), insects, and birds. The conversion from ferrltin-llke iron cores requires partial changes in the oxidation state of and/or ordering of the iron atoms, and may depend on some of the natural variations in ferritin core structure. 

The carbohydrate components of hard-pieces of invertebrates have been reviewed recently416. Sulfated polysaccharides have been identified as Ca-binding sites of septal nacre from Nautilus pompilius430 This indicates that the site is a sulfated polysaccharide (s), and may be a sulfated, calcium-binding glycoprotein similar to the one isolated from Mercenaria mercenaria414 ... 

In plants, certain invertebrates, and some microorganisms (including E. coli and yeast) acetate can serve both as an energy-rich fuel and as a source of phosphoenolpyruvate for carbohydrate synthesis. In these organisms, enzymes of the glyoxylate cycle catalyze the net conversion of acetate to succinate or other four-carbon intermediates of the citric acid cycle ... 

Metabolites of the phylum Porifera account for almost 50% of the natural products reported from marine invertebrates. Of the 2609 poriferan metabolites, 98% are derived from amino acid, acetogenin, or isoprenoid pathways. Isoprenoids account for 50% of all sponge metabolites, while amino acid and polyketide pathways account for 26% and 22%, respectively. A significant number of sponge metabolites appear to be derived from mixed biosynthetic pathways. Most structures reported containing carbohydrate moieties were glycosides. 

As with natural antifoulants, there are few (if any) fully documented examples of natural, ecologically relevant inducers of settlement that is, characterized cues which induce settlement, have been quantified in situ, are active at in situ concentrations against the relevant target organism, and can be related to patterns in the demography of that organism. However, there are a wealth of examples, particularly for invertebrates, in which various pieces of this puzzle are known, and that information is summarized here. The information that is available points to the widespread use of primary metabolites, particularly water-soluble (polar) peptides and carbohydrates, as natural cues. 

Definitive chemical analyses of the nature of compounds produced by biofilm bacteria that induce settlement and metamorphosis of invertebrates are generally lacking. Peptides, supposedly arising from biofilm bacteria and having the capacity to induce settlement of oyster larvae, were described by Zimmer-Faust and Tamburri18 (discussed above in Section III.C). Studies of larval settlement in the spirorbid polychaete Janua brasiliensis have indicated that its alga-specific settlement is, in fact, mediated by carbohydrate moieties of the exopolymers of biofilm bacteria.173... 

The above complex means by which fats are mobilized contrast strikingly with the way carbohydrates are mobilized in large part due to the different chemical properties of glucose versus FFAs. As in the case of FFAs, carbohydrates often need to be mobilized from a central depot (in this case, the liver) to sites of utilization at working tissues and the transported metabolite in animals is almost always glucose (there are some invertebrates which use trehalose or galactose). Glucose is a very water... 

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