Rice and Genetic Engineering essays

Rice and Genetic Engineering essays Rice is the main food for about one-third to one-half of the world's population. A mature rice plant is usually two to six feet tall. In the beginning, one shoot appears. It is followed by one, two, or more offshoots developing. There are at least five or six hollow joints for each stalk, and a leaf for each joint. The leaf of the rice plant is long, pointed, flat, and stiff. The highest join of the rice plant is called the panicle. The rice grains develop from the panicles. (Jodon, 300) Rice is classified in the grass family Gramineae. Its genus is Oryza and species O. sativa. It is commonly cultivated for food in Asia. Some varieties of rice include red rice, glutinous rice, and wild rice. (Jodon, 303) The kernel within the grain contains most of the vitamins and minerals (298). The kernel contains thiamine, niacin, and riboflavin (299). Rice has many enemies that destroy a majority of the rice crops. The larvae of moth, stem borers, live in the stems of the rice plants. Some insects suck the plant juices or chew the leaves. Birds, such as bobolink, Java sparrow, or paddybird, would eat the seeds or grains. Disease causing factors such as fungi, roundworms, viruses, and bacteria also destroy the rice plants. Blast disease is caused by fungi which causes the panicles containing the grains to break. (Jodon, 300) There are various types of rice grown all over the world. A majority of rice grown is cultivated rice. When rice is grown with water standing on the fields, it is called lowland, wet, or irrigated rice. Rice plants grown in certain parts of Asia, South America, and Africa are called upland, hill, or dry rice because they are raised on elevated lands that cannot be flooded, but with plentiful rainfall. Wild rice is grown along lake shores of Canada and the Great Lakes. It is usually eaten by people in India. Scented rice is the most expensive because is has long grains and tastes like p...

Introduction to Monomers and Polymers in Chemistry

Introduction to Monomers and Polymers in Chemistry A monomer is a type of molecule that has the ability to chemically bond with other molecules in a long chain; a polymer is a chain of an unspecified number of monomers. Essentially, monomers are the building blocks of polymers, which are more complex type of molecules. Monomers- repeating molecular units- are connected into polymers by covalent bonds. Monomers The word monomer comes from mono- (one) and -mer (part). Monomers are small molecules which may be joined together in a repeating fashion to form more complex molecules called polymers. Monomers form polymers by forming chemical bonds or binding supramolecularly through a process called polymerization. Sometimes polymers are made from bound groups of monomer subunits (up to a few dozen monomers) called oligomers. To qualify as an oligomer, the properties of the molecule need to change significantly if one or a few subunits are added or removed. Examples of oligomers include collagen and liquid paraffin. A related term is monomeric protein, which is a protein that bonds to make a multiprotein complex. Monomers are not just building blocks of polymers, but are important molecules in their own right, which do not necessarily form polymers unless the conditions are right. Examples of Monomers Examples of monomers include vinyl chloride (which polymerizes into polyvinyl chloride or PVC), glucose (which polymerizes into starch, cellulose, laminarin, and glucans), and amino acids (which polymerize into peptides, polypeptides, and proteins). Glucose is the most abundant natural monomer, which polymerizes by forming glycosidic bonds. Polymers The word polymer comes from poly- (many) and -mer (part). A polymer may be a natural or synthetic macromolecule comprised of repeating units of a smaller molecule (monomers). While many people use the term polymer and plastic interchangeably, polymers are a much larger class of molecules which includes plastics, plus many other materials, such as cellulose, amber, and natural rubber. Lower molecular weight compounds may be distinguished by the number of monomeric subunits they contain. The terms dimer, trimer, tetramer, pentamer, hexamer, heptamer, octamer, nonamer, decamer, dodecamer, eicosamer reflects molecules containing 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, and 20 monomer units. Examples of Polymers Examples of polymers include plastics such as polyethylene, silicones such as silly putty, biopolymers such as cellulose and DNA, natural polymers such as rubber and shellac, and many other important macromolecules. Groups of Monomers and Polymers The classes of biological molecules may be grouped into the types of polymers they form and the monomers that act as subunits: Lipids - polymers called diglycerides, triglycerides; monomers are glycerol and fatty acidsProteins - polymers are known as polypeptides; monomers are amino acidsNucleic Acids - polymers are DNA and RNA; monomers are nucleotides, which are in turn consist of a nitrogenous base, pentose sugar, and phosphate groupCarbohydrates - polymers are polysaccharides and disaccharides*; monomers are monosaccharides (simple sugars) *Technically, diglycerides, and triglycerides are not true polymers because they form via dehydration synthesis of smaller molecules, not from the end-to-end linkage of monomers that characterizes true polymerization. How Polymers Form Polymerization is the process of covalently bonding the smaller monomers into the polymer. During polymerization, chemical groups are lost from the monomers so that they may join together. In the case of biopolymers of carbohydrates, this is a dehydration reaction in which water is formed. Resources and Further Reading Cowie, J.M.G. and Valeria Arrighi. Polymers: Chemistry and Physics of Modern Materials, 3rd ed. Boca Taton: CRC Press, 2007.  Sperling, Leslie H. Introduction to Physical Polymer Science, 4th ed. Hoboken, NJ: John Wiley Sons, 2006.  Ã‚  Young, Robert J., and Peter A. Lovell. Introduction to Polymers, 3rd ed. Boca Raton, LA: CRC Press, Taylor Francis Group, 2011.