Carbohydrates living systems

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... 

Biopolymers are the naturally occurring macromolecular materials that are the components of all living systems. There are three principal categories of biopolymers, each of which is the topic of a separate article in the Eniyclopedia proteins (qv) nucleic acids (qv) and polysaccharides (see Carbohydrates Microbial polysaccharides). Biopolymers are formed through condensation of monomeric units ie, the corresponding monomers are amino acids (qv), nucleotides, and monosaccharides, for proteins, nucleic acids, and polysaccharides, respectively. The term biopolymers is also used to describe synthetic polymers prepared from the same or similar monomer units as are the natural molecules. 

Photosynthesis takes atmospheric carbon dioxide and incorporates it into organic molecules—the carbon dioxide is fixed into the carbohydrate. These molecules are then either converted into chemical energy or used as structural molecules. The first powers living systems the second is what living systems are composed of. 

Adds of non-carbohydrate origin which are produced by all living systems. 

Adds of carbohydrate origin which are constantly produced by living systems and are not considered as waste products. 

Carbohydrates play an indispensable role on the stage of life. These molecules provide for several critical functions in living systems. Among these functions are maintenance of structure, energy storage and supply, and intercellular signaling. 

Three published papers (110-112) and the chapter of a Ph.D. thesis (46) have reported VCD results in carbohydrates. The significance of these studies derives from the important biological roles that carbohydrates play in living systems. All three contributions are concerned with either sugars or their derivatives. From a structural point of view these molecules are quite interesting due to the presence of several adjacent stereogenic centers and the availability of different... 

The molecules that form the foundation of living systems are often organized into four categories. They are the primary metabolites nucleic acids, proteins, carbohydrates, and lipids. The categories can be grouped together in different ways, based on features that they have in common. For example, nucleic acids, proteins, and polysaccharides are polymeric. Nucleic acids and proteins are further related because they are templated polymers. Other classification systems are also possible.1 Interest in the development of size-expanded versions of biomolecules has grown over the past... 

Glycoside hydrolases (glycosidases) are essential and consequently widely abundant enzymes in all living systems that rely on the processing of carbohydrates. From the degradation of such polysaccharides as starch, cellulose, or chitin to the highly... 

In this section, enzymes in the EC 2.4. class are presented that catalyze valuable and interesting reactions in the field of polymer chemistry. The Enzyme Commission (EC) classification scheme organizes enzymes according to their biochemical function in living systems. Enzymes can, however, also catalyze the reverse reaction, which is very often used in biocatalytic synthesis. Therefore, newer classification systems were developed based on the three-dimensional structure and function of the enzyme, the property of the enzyme, the biotransformation the enzyme catalyzes etc. [88-93]. The Carbohydrate-Active enZYmes Database (CAZy), which is currently the best database/classification system for carbohydrate-active enzymes uses an amino-acid-sequence-based classification and would classify some of the enzymes presented in the following as hydrolases rather than transferases (e.g. branching enzyme, sucrases, and amylomaltase) [91]. Nevertheless, we present these enzymes here because they are transferases according to the EC classification. 

Carbohydrates form the major structural components of the cell walls. The most common form is cellulose which makes up over 30 per cent of the dry weight of wood. Other structural forms are hemicellulose (a mixed polymer of hexose and pentose sugars), pectins and chitin. Apart from contributing to the structure, some polymers also act as energy storage materials in living systems. Glycogen and starch form the major carbohydrate stores of animals and plants, respectively. Carbohydrate structure, like that of nucleic acids and proteins, is complex, and various levels of structure can be identified. 

This text is divided into seven parts part l, An Overview of Biochemical Structures and Reactions That Occur in Living Systems part 2, Protein Structure and Function part 3, Catalysis part 4, Metabolism of Carbohydrates part 5, Metabolism of Lipids part 6, Metabolism of Nitrogen-Containing Compounds and part 7, Storage and Utilization of Genetic Information. 

In addition, in living systems, most biochemical reactions, including ATP hydrolysis, take place during the catalysis of enzymes. The catalytic action of enzymes allows the hydrolysis of proteins, fats, oils, and carbohydrates. As an example, one may consider proteases, enzymes that aid digestion by hydrolyzing peptide bonds in proteins. They catalyze the hydrolysis of interior peptide bonds in peptide chains, as opposed to exopeptidases, another class of enzymes, that catalyze the hydrolysis of terminal peptide bonds, liberating one free amino acid at a time. 

There are four basic kinds of organic molecules that exist in large quantities in organisms or living systems carbohydrates, lipids, proteins, and nucleotides. These combine with water, which makes up between 50 and 95% of the volume of most cells. 

Carbon is present in all living cells as the element in carbohydrates, proteins, lipids, etc. Without carbon we would not exist. Carbon dioxide is exhaled by all animals and used by green plants to synthesize carbohydrates. There is a constant exchange of carbon in living systems... 

Lipids (see Fig. 1) (1) constitute one of five classes of molecules that can be considered as crucial in biological systems. Together with proteins, nucleotides (DNA), carbohydrates, and water, lipids can be thought of as one of the basic building blocks of living systems. 

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