first test[1] - Chapter 2 -Of the 92 elements that occur...

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Chapter 2 -Of the 92 elements that occur naturally on the earth, only six were selected in the course of evolution to form complex, highly organized material of living organisms. These siz are carbon, hydrogen, nitrogen, oexygen, phosphorus, and sulfur – make up 99 percent of the weight of all living matter. -Of the thousands of different organic molecules found in cells, just four different types make up most of the dry weight of living organisms. They are Carbohydrates (consisting of sugars and chains of sugars), lipids (most of which contain fatty acids), proteins (composed of amino acids), and nucleic acids (DNA and RNA, which are made up of complex molecules known as nucleotides). All of these molecules consist mainly of carbon and hydrogen and most of them contain oxygen as well. Carbohydrates Carbohydrates are the most abundant organic molecules in nature and are the primary energy-storage molecule in most living organisms. The walls of young plants cells, for example, are made up of the universally important carbohydrate cellulose embedded in a matrix of other carbohydrates and proteins. --the simplest carbohydrates are small molecules know as sugars; larger carbohydrates are composed of sugars joined together. There are three principal kinds of carbohydrates, classified according to the number of sugar subunits they contain. Monosaccharides (“single, or simple, sugars”), such ass ribose, and glucose, and fructose, consist of only one sugare molecule. Monosaccharides are the simplest carb. The are proportioned by one carbon atom to two hydrogen atoms to one oxygen atom. Summed up by the formula (CH2O)n, where n can be as small as 3, as in C3H6O3, or as large as 7, as in C7H12O7. These proportions gave rise to the term carbohydrate, meaning “carbon with water added”. Each monosaccharide chain as a carbon backbone. Attached to each carbon, except one, is –OH. The last carbon is double bonded to an oxygen atom(C=O). Both carbon bonds (-OH and C=O) are hydrophilic, thus monosaccharides as well as many other carbs readily dissolve in water. Fig 2-2 shows how carbs can be either chain form or ring form (when dissolved in water they are normally found in ring form). Disaccharides (“two sugars”) contain two sugar subunits linked covalently. Familiar examples are sucrose (table sugar), and lactose (milk sugar). Although glucose in the common transport for sugar for many animals, sugars are often transported in plants and other organisms as a disaccharides. Sucrose , a disaccharide composed of glucose and fructose, is the from in which sugar is transported in most plants from the photosynthetic cells (primarily in the leaves), where it is produced, to other parts of the plant body. In the synthesis of a disaccharide from two monosaccharide molecules, a molecule of water is removed and j a new bond is formed between the two monosacchardies. This type of chemical reaction, which occurs when sucrose is formed from glucose and fructose, is know as
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This note was uploaded on 04/07/2008 for the course BIO 2000 taught by Professor Zacm during the Spring '08 term at Appalachian State.

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first test[1] - Chapter 2 -Of the 92 elements that occur...

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