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BSC-1010L Chemistry of Life-2

BSC-1010L Chemistry of Life-2 - LAB 4 THE CHEMISTRY OF LIFE...

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LAB 4: THE CHEMISTRY OF LIFE Introduction Organic molecules are molecules that contain carbon and hydrogen . All living things contain these organic molecules: carbohydrates , lipids , proteins , and nucleic acids . These molecules are often called macromolecules because they may be very large, containing thousands of carbon and hydrogen atoms and because they are typically composed of many smaller molecules bonded together. Hydrophilic and Hydrophobic Pola r and ionic molecules have positive and negative charges and are therefore attracted to water molecules because water molecules are also polar. They are said to be hydrophilic because they interact with (dissolve in) water by forming hydrogen bonds. Nonpolar molecules are hydrophobic (means "water fearing"). They do not dissolve in water. Nonpolar molecules are hydrophobic. Polar and ionic molecules are hydrophilic. Portions of large molecules may be hydrophobic and other portions of the same molecule may be hydrophilic. Macromolecules and Monomers Many of the common large biological molecules (macromolecules) are synthesized from simpler building blocks (monomers). Each of the types of molecules listed in the table are discussed below. Example of a Macromolecule Monomer polysaccharide (complex carbohydrate) monosaccharide (simple carbohydrate, sugar) fat (a lipid) glycerol, fatty acids protein amino acids (20 different ones) nucleic acids DNA or RNA DNA or RNA nucleotides CARBOHYDRATES The general formula for carbohydrates is (CH 2 O) n . Monosaccharides Monosaccharides are simple sugars, having 3 to 7 carbon atoms. They can be bonded together to form polysaccharides . The names of most sugars end with the letters ose . EXAMPLE Glucose , fructose, and galactose are monosaccharides; their structural formula is C 6 H 12 O 6 . Glucose and other kinds of sugars may be linear molecules as shown below but in aqueous solution they become a ring form 1
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. Simple sugars store energy for cells. Details concerning energy storage and release by glucose are in the chapter on cellular respiration. Cells also use simple sugars to construct other kinds of organic molecules. Disaccharides Disaccharides are composed of 2 monosaccharides joined together by a condensation reaction (removal of water when two monomers are joined) Examples: Sucrose (table sugar) is composed of glucose and fructose. Like glucose, sucrose stores energy. Plants synthesize sucrose to transport to nonphotosynthetic parts of the plant. Lactose is found in milk. It is formed when glucose bonds to galactose. The digestion of carbohydrates typically involves hydrolysis reactions in which complex carbohydrates (polysaccharides) are broken down to maltose (a disaccharide). Maltose is then further broken down to produce two glucose molecules, again by hydrolysis. Hydrolysis is the opposite of condensation to break the bonds we add the water taken away during condensation back. Polysaccharides
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BSC-1010L Chemistry of Life-2 - LAB 4 THE CHEMISTRY OF LIFE...

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