Crabs, exoskeleton

Except for crab exoskeletons, gold recovery from the medium by various species of living molluscs, crustaceans, and fishes is negligible. The maximum concentration of stable gold measured in tissues of living marine organisms was 38.0 xg/kg FW. 

Glucose molecules can link together into chains, with each ring tethered to the next by a bridging oxygen atom. In one form, this is cellulose, the stiff material that gives the stalks of plants and the trunks of trees their structural strength. Chitin, a variation on cellulose, is an even stiffen material that forms the exoskeletons of crustaceans such as crabs and lobsters. 

Christiansen, M.E. and J.D. Costlow, Jr. 1982. Ultrastructural study of the exoskeleton of the estuarine crab Rithropanopeus harrisii effect of the insect growth regulator dimilin (diflubenzuron) on the formation of the larval cuticle. Mar. Biol. 66 217-226. 

Plutonium-237, dose unknown were 145 in whole crab, 960 in gills, and 240 in exoskeleton 50% elimination in 45 days After 8 days, BCF values were 75 in whole 8... 

Daphnid, Daphnia pulex, daily exposure to crab, 340 in gills, and 70 in exoskeleton 50% elimination in 55 days Increased growth rate 1... 

Chitin is a polysaccharide similar to cellulose except that the OH at C-2 is replaced by an acetamido group (CH3CONH). Chitin is the main component of the hard external covering (exoskeleton) of crustaceans such as lobsters, crabs, and shrimp. Like cellulose, the processing of chitin into polymeric products is limited by its insolubility and decomposition without melting. The availability in huge quantities has encouraged many attempts to find commercial applications of chitin, but very few have been found to be economically feasible. 

The exoskeleton of the crab and other crustaceans is primarily composed of a substance called chitin. This is a giant molecule made up of fundamental units of N-acetyglucosamine strung together like links in a chain. Chitin is abundantly available, thanks to a crab and lobster industry dedicated to making it easier for us to consume their products by removing the... 

Chitin is a linear homopolysaccharide composed of Af-acetylglucosamine residues in /3 linkage (Fig. 7-18). The only chemical difference from cellulose is the replacement of the hydroxyl group at C-2 with an acety-lated amino group. Chitin forms extended fibers similar to those of cellulose, and like cellulose cannot be digested by vertebrates. Chitin is the principal component of the hard exoskeletons of nearly a million species of arthropods—insects, lobsters, and crabs, for example— and is probably the second most abundant polysaccharide, next to cellulose, in nature. 

The exoskeletons (protective shells) of insects and some marine organisms, such as crabs and shrimp, are made of chitin, a hard, resilient polysaccharide made of the monosaccharide A acetylglucosamine, as shown in Figure 13.5b. Wood varnish once contained chitin from the exoskeletons of insects. In powdered form, chitin is now finding use as a dietary fiber supplement. 

Chitin is a polysaccharide constituted of N -acctylglucosamine, which forms a hard, semitransparent biomaterial found throughout the natural world. Chitin is the main component of the exoskeletons of crabs, lobsters and shrimps. Chitin is also found also in insects (e.g. ants, beetles and butterflies), and cephalopods (e.g. squids and octopuses) and even in fungi. Nevertheless, the industrial source of chitin is mainly crustaceans. 

The exoskeletons of shellfish such as crabs and lobsters as well as many insects contain a high concentration of chitin, which is very similar to cellulose (b 1,4-glycoside linkages), except that instead of an OH group at carbon-2, chitin has a substituted amine group (an amide) ... 

The Crustacea is the second largest group within the Arthropods. This diverse group includes lobsters, crabs, shrimp, sow bugs, barnacles, and many other forms. Over 38,000 species of Crustacea are known and there are probably many more yet to be discovered. Most Crustacea have a hard chitinous exoskeleton, three body segments, two pairs of antennae, and gills for breathing. Most... 

Chitin is one of the main components in the cell walls of fungi and the exoskeletons of insects and other arthropods (you know, crabs and stuff). It is strong and relatively rigid and helps protect an insect against harm and pressure. The rigidity of a biological structure made from chitin depends on its thickness. Often, insect coats contain thick, stiff layers of chitin, while the areas around the legs and face contain very thin, pliable layers. 

Chitin is isolated from the exoskeletons of crustaceans (e.g., crabs, lobsters, crayfish, shrimp, krill, barnacles), molluscs or invertebrate animals (e.g., squid, octopus, cuttlefish, nautilus, chitons, clams, oysters, scallops. 

Chitin is another highly available polysaccharide biopolymer it is derived from the exoskeleton of arthropods (specifically crab and shrimp shells) and formed from repeats of (l,4)-linked V-acetyl-p-D-glucosamine. In its natural form, the chains of... 

Carbohydrate I A chemical compound made up of a chain or ring of carbon atoms to which hydrogen and oxygen atoms are attached in a defined ratio (2 1) includes simple sugars like glucose and complex sugars like chitin (the exoskeleton of crabs). 

This nitrogen-containing polysaccharide makes up the shells of lobsters, crabs, and the exoskeletons of insects. Draw a portion of a chitin polymer consisting of four monomers. 

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