Structure of Di Saccharides and Polysaccharides

 Structure of Di-Saccharides and Polysaccharides

Disaccharides are formed by the condensation of two monosaccharide molecules. These monosaccharides join together by the loss of a water molecule between one hydroxyl groups on each monosaccharide. Such a linkage, which joins the monosaccharide units together, is called glycoside linkage. If two α-glucose molecules are joined together, the disaccharide maltose is formed


Similarly, sucrose (the common sugar) consists of one molecule of glucose and one molecule of fructose joined together. Lactose (or milk sugar) is found in milk and contains one molecule of glucose and one molecule of galactose. If a large number of monosaccharide units are joined together, we get polysaccharides. These are the most common carbohydrates found in nature. They have mainly one of the following two functions- either as food materials or as structural materials. Starch is the main food storage polysaccharide of plants. It is a polymer of α-glucose and consists of two types of chains- known as amylose and amylopectin. Amylose is a water soluble fraction of starch and is a linear polymer of α-D-glucose. On the other hand amylopectin is a water insoluble fraction and consists of branched chain of α-D-glucose.

The carbohydrates are stored in animal body as glycogen which is also a polymer of α -glucose and its structure is similar to amylopectin.


Cellulose is another natural polysaccharide which is the main component of wood and other plant materials. It consists of long chain of ß-D-glucose molecules.

Comments

Post a Comment

Popular posts from this blog

Tautomerism

Image
  Tautomerism The nitrogenous bases in nucleosides and nucleotides, with the exception of adenine and adenosine, undergo enol-keto tautomerism. Studies have shown that the predominant species in solution is the keto form. Examples are uracil and guanine. Biological Functions of Nucleic Acids DNA is the chemical basis of heredity and may be regarded as the reserve of genetic information. DNA is exclusively responsible for maintaining the identity of different species of organisms over millions of years. A DNA molecule is capable of self duplication during cell division and identical DNA strands are transferred to daughter cells. Another important function of nucleic acids is the protein synthesis in the cell. Actually, the proteins are synthesised by various RNA molecules in the cell but the message for the synthesis of a particular protein is present in DNA.
Read more

More ‘Friendly’ Selectable Markers: the Positive Selection Method - Plant Transgenics

  More ‘Friendly’ Selectable Markers: the Positive Selection Method In contrast to the traditional selection where the transgenic cells acquire the ability to survive on selective media while the non-transgenic cells are killed (negative selection), the positive selection method, first developed by Joersbo and Okkels (1996) favors regeneration and growth of the transgenic cells while the non-transgenic cells are starved but not killed. The positive selection method exploits the fact that cytokinin must be added to plant explants in order to obtain optimal shoot regeneration rates. By adding cytokinin as an inactive glucuronide derivate, cells which have acquired the  GUS  gene by transformation are able to convert the cytokinin glucuronide to active cytokinin while untransformed cells are arrested in development. In this system,  GUS  serves the dual purpose of being both a selectable and screenable marker gene. Another interesting system of positive selection uses the xylose isomerase
Read more

Computer Applications and Biostatistics

  Computer Applications and Biostatistics        Computer application in biology is a complex blend of two distinct scientific disciplines – computer technology and life science. The field of biology is invariably depended on statistics too giving rise to biostatistics. The amalgam of computer applications and biostatistics in combination with several scientific fields gave birth to an interdisciplinary field called bioinformatics, which reaches the biological predictions in an  in silico  way in combination with statistics. Advancement of computer technology has led a path for biological researches giant leap. Progress in the basic functionalities of a computer like store, process, retrieve and reuse, has led to well a synchronized interplay of biology, computing technology and statistics. Biological data is extensive and heterogeneous ranging from text based genome sequences, geometric and spatial information to patterns, large images and simulation. Such a magnitude of information h
Read more