5-Biological Molecules-Fall-2005

5-Biological Molecules-Fall-2005 - Intro. Biol. Course...

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Intro. Biol. Course Guide Sathasivan, 2005 Chap. 5. Biological Molecules 1 5. BIOLOGICAL MOLECULES Outline I. Condensation Synthesis and Hydrolysis II. Carbohydrates III. Lipids IV. Proteins V. Nucleic Acids II. Condensation Synthesis and Hydrolysis As we discussed biological hierarchy in the first chapter, atoms combine to form molecules that are used to build macromolecules such as DNA, RNA, proteins, carbohydrates and lipids, all of which form the building blocks of life. The four major groups of biological molecules are carbohydrates, lipids, proteins and nucleic acids. Each part of the cell is composed of several different types of biological molecules. Some of the biological molecules are small and they are used as monomers to make larger molecules. Some are very large (1000s of Daltons) and are called as macromolecules. The size limit for macromolecules is an arbitrary one. Simple sugars, amino acids, nucleotides and almost all lipids are relatively very small compared to the macromolecules such as polysaccharides, polypeptides (proteins), DNA and RNA. Atoms Molecule Macromolecule (C, H, O) (C 6 H 12 O 6 ) (Polysaccharide) Natural Made by Made by enzymes via occurrence enzymes condensation synthesis The individual units that make a large molecule are called monomers. Monomers typically contain –H and –OH groups attached to them. Two monomers are combined in a condensation reaction to make a dimer by the removal of an -H and an -OH group, which condense to form a water (H 2 O) molecule. More monomers are added in a similar reaction to synthesize polymers. HO H HO H + H HO H O 2 Condensation synthesis of a macromolecule is performed by a specific enzyme that uses specific monomers to make that polymer. The condensation synthesis process creates bonds between the monomers in carbohydrates, lipids, and proteins. Nucleic acids are polymerized by a nucleophilic attack, but the reaction is similar to condensation synthesis. Hydrolysis : It breaks down dimers, trimers or polymers into monomers by adding an -H and an -OH group derived from the splitting of a
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Intro. Biol. Course Guide Sathasivan, 2005 Chap. 5. Biological Molecules 2 water molecule (hydrolysis). This is important for catabolic processes that utilize the energy stored in different macromolecules. Hydrolysis of a macromolecule is performed by a specific enzyme, e.g., cellulose is degraded by cellulase and DNA is degraded by DNase. Almost all enzymes are proteins catalyzing a reaction. Their names usually end with the suffix “ase” except when ‘ase’ is preceded by capital ‘A’. In such a situation, the capital ‘A’ is deleted, e.g., DNAase changes to DNase. II. CARBOHYDRATES Monosaccharides These simple sugars are the monomers (single units) that make up complex carbohydrates with many units.
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5-Biological Molecules-Fall-2005 - Intro. Biol. Course...

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