Plants structural components

The major classes of organic compounds common to living systems are lipids pro terns nucleic acids and carbohydrates Carbohydrates are very familiar to us— we call many of them sugars They make up a substantial portion of the food we eat and provide most of the energy that keeps the human engine running Carbohy drates are structural components of the walls of plant cells and the wood of trees Genetic information is stored and transferred by way of nucleic acids specialized derivatives of carbohydrates which we 11 examine m more detail m Chapter 28... 

The fire department blamed the accident on welders cutting in hazardous areas without a fire watch, highly combustible structural components (fiber-glass-resin), high-density storage of highly flammable and detonable material, spilled ammonium perchlorate about the plant, and high w ind conditions. 

The fragility analysis evaluates the conditional fraction of failure of plant structures and equipment as a function of ground motion. The seismically initiated failure of plant components is expressed in terms spectral acceleration at 5.0 Hz which is between the fundamental frequency of the... 

Carotenoids protect photosynthetic organisms against potentially harmful photooxidative processes and are essential structural components of the photosynthetic antenna and reaction center complexes. Plant carotenoids play fundamental roles as accessory pigments for photosynthesis, as protection against photooxidation, and... 

Carbohydrates Sugars, starch, cellulose Structural components of plant cells easily released energy storage in plants and animals Sugars in fruits starch and cellulose in plants glycogen in animals below 1... 

Plants were probably the first to have polyester outerwear, as the aerial parts of higher plants are covered with a cuticle whose structural component is a polyester called cutin. Even plants that live under water in the oceans, such as Zoestra marina, are covered with cutin. This lipid-derived polyester covering is unique to plants, as animals use carbohydrate or protein polymers as their outer covering. Cutin, the insoluble cuticular polymer of plants, is composed of inter-esterified hydroxy and hydroxy epoxy fatty acids derived from the common cellular fatty acids and is attached to the outer epidermal layer of cells by a pectinaceous layer (Fig. 1). The insoluble polymer is embedded in a complex mixture of soluble lipids collectively called waxes [1], Electron microscopic examination of the cuticle usually shows an amorphous appearance but in some plants the cuticle has a lamellar appearance (Fig. 2). 

The major function of cutin is to serve as the structural component of the outer barrier of plants. As the major component of the cuticle it plays a major role in the interaction of the plant with its environment. Development of the cuticle is thought to be responsible for the ability of plants to move onto land where the cuticle limits diffusion of moisture and thus prevents desiccation [141]. The plant cuticle controls the exchange of matter between leaf and atmosphere. The transport properties of the cuticle strongly influences the loss of water and solutes from the leaf interior as well as uptake of nonvolatile chemicals from the atmosphere to the leaf surface. In the absence of stomata the cuticle controls gas exchange. The cuticle as a transport-limiting barrier is important in its physiological and ecological functions. The diffusion across plant cuticle follows basic laws of passive diffusion across lipophylic membranes [142]. Isolated cuticular membranes have been used to study this permeability and the results obtained appear to be valid... 

The passage from the lst-generation of biofuels, which use agricultural products, to 2 nd-generation biofuels that use all the structural components of plants and trees, e.g., able to process (ligno)cellulose, requires the following developments ... 

In terms of function, polysaccharides fall into one of two groups structural and nutritional. For example, cellulose is a principal structural component of plants. Glycogen and starch, in contrast, are nutritional reservoirs for animals and plants, respectively. Monosaccharides may be mobilized from storage reservoirs such as glycogen and starch and then be metabolized to generate energy. 

Iron Present in most animal and plant foods Involved in >300 metabolic reactions energy metabolism Structural component of DNA and RNA... 

Carbohydrates are the most abundant organic component of plants. Structurally, carbohydrates are usually polyhydroxy aldehydes or polyhydroxy ketones (or compounds that hydrolyze to yield polyhydroxy aldehydes and ketones). Since carbohydrates contain carbonyl groups and hydroxyl groups, they exist primarily as acetals or hemiacetals. 

Carbon metabolism differs fundamentally from nitrogen metabolism In that virtually all nitrogenous compounds can be recycled within the plant, whereas most of the structural components of the plant, principally cellulose and lignin, are not reusable. There are also putative defensive compounds In this category such as leaf-external resins (32) and possibly some condensed tannins. Thus the constraints on allocation have both an Immediate and future time frame. 

Cellulose is the most abundant naturally occurring organic material. It acts as the main structural component in higher plants. The purest form of cellulose is derived from the seed hairs of the cotton plant, which contains 95% cellulose. 

In all, 40 families had more than 50% of their genera sampled, and 23 families had more than 100 samples each (Table 3.2). These were primarily families of woody plants that are important structural components of forests, are species that lend themselves to being divided into component samples, and are often of widespread taxa. Of families with 50% or more of their genera collected, only Marantaceae, Commelinaceae, and Polygalaceae are primarily herbaceous and represent only 32 of the 722 genera in these 40 families. In addition, Acanthaceae and Asteraceae were the only primarily herbaceous families from which more than 100 samples had been collected, but both are very large families that are well represented in the flora of tropical Africa. 

FIGURE 1-12 Elements essential to animal life and health. Bulk elements (shaded orange) are structural components of cells and tissues and are required in the diet in gram quantities daily. For trace elements (shaded bright yellow), the requirements are much smaller for humans, a few milligrams per day of Fe, Cu, and Zn, even less of the others. The elemental requirements for plants and microorganisms are similar to those shown here the ways in which they acquire these elements vary. 

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