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Unformatted text preview: Chapter 3—Biological Molecules • Aside from water, most biologically related molecules contain carbon. o Organic molecules are molecules containing carbon. o Carbon atoms are the most versatile building blocks of molecules Carbon has a valence of 4—it can bind to 2, 3, or 4 other atoms. • Another factor which leads to the versatility of organic molecules is the attachment of functional groups —small characteristic groups of atoms which are frequently bonded to the carbon skeleton of organic molecules. • Functional Groups o Characteristics of functional groups: Have specific chemical and physical properties. Are regions of organic molecules, which are frequently chemically reactive. Behave consistently from one organic molecule to another. Can determine the chemical properties of the organic molecule in which they are located. o 1) Hydroxyl Group (—OH) A functional group of a hydrogen atom bonded to an oxygen atom which is bonded to a carbon atom (of the carbon skeleton). • A polar group. • Involved in dehydration and hydrolysis reactions. o 2) Carbonyl Polar functional group. Extremely hydrophilic. Makes parts of a molecule water soluble. o 3) Carboxyl (—COOH) A functional group in which a carbon atom is double bonded to an oxygen atom (like a carbonyl) and is also single bonded to the oxygen atom of a hydroxyl group. • Since this group can donate a proton, it’s acidic. • Involved in peptide bonds between amino acids. o 4) Amino (—NH2) Functional groups in which two hydrogen atoms are bonded to a nitrogen atom which is bonded to a carbon atom (of the carbon skeleton). • Acts a weak base (similar to ammonia) because it accepts protons. • Involved in peptide bonds between amino acids. o 5) Sulfhydryl (—S-H) Forms disulfide bonds within and between proteins. Found in numerous proteins in biological systems. o 6) Phosphate (—H2PO4) A functional group which is the dissociated form of phosphoric acid (H3PO4) Acts as an acid because of the ability to donate protons. Links nucleotides together to form nucleic acids. Important in cellular energy storage and energy transfer—ATP. • Synthesizing Organic Molecules: A Modular Approach o Biological molecules are often put together in subunits , or modules, called monomers. The simple molecules combined to form more complex ones. • Monomers to polymers. o Polymers are chains of similar building blocks or monomers. o Polymerization —the bonding of many small subunits (monomers) to form long molecules (polymers). o The reaction that forms a polymer from monomers is dehydration synthesis —a reaction in which the covalent linkage of the monomers is accompanied by the “removal” of a water molecule....
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This note was uploaded on 10/30/2011 for the course BIOLOGY 1001 taught by Professor Crousillac during the Summer '10 term at LSU.
- Summer '10
- Organic Molecules