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Chemistry of Microbes LECTURES IN MICROBIOLOGY LECTURES IN MICROBIOLOGY LESSON 2 Sofronio Agustin Professor Sofronio Agustin Professor
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2 Topics Fundamental Building Blocks Macromolecules The Cell
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3 Fundamental Building Blocks Atoms Elements Molecules and compounds
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4 Atoms Subatomic Particles Proton = positive charge Neutron = neutral Electron = negative charge Atomic number = no. of protons Atomic mass = no. of protons and neutrons
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5 Models of Atomic Structure Atomic Structure
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6 Isotopes Atoms with same number of protons but differ in number of neutrons are called isotopes. Example: 12 C, 13 C, and 14 C are isotopes of carbon. Radioisotopes emit radiation in the form of alpha or beta or gamma rays or photons.
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7 Major Elements of Life
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8 Molecules and Compounds Molecule = combination of two or more elements (e.g.H 2 ) Compound = combination of two or more different elements (e.g. H 2 O) Molecules are held together by chemical bonds
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9 Chemical Bonds Covalent Ionic Hydrogen
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10 Chemical Bonds Chemical bonds involve atoms sharing, donating or accepting electrons
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11 Covalent Bonding Examples of covalent bonding
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12 Polar Covalent Bond Polarity occurs when atoms electrons unequally due to differences in electronegativities. This is seen in water (H 2 O). More electronegative atoms tend to pull electrons toward them creating a polar molecule.
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13 Ionic Bonding Sodium chloride (table salt) is an example of ionic bonding, that is, electron transfer among atoms or redox reaction.
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14 Ionization Molecules formed by ionic bonding breakup (ionization) when dissolved in water (solvent), producing separate positive (cation) and negative (anion) ions. These ions conduct electricity and thus called electrolytes.
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15 Hydrogen Bond Hydrogen bonding is formed between the partially positive (hydrogen) end of a polar molecule and the negative end of another (e.g. O 2 or N 2 ). Example : Water molecules
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16 pH pH – measurement of the H + ion concentration in a solution. General rule: Acidic = excess H + ions in solution Basic = excess OH - ions in solution Neutral = equal amounts of H + and OH - ions
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17 The pH Scale The pH of an environment (exterior or interior of a cell) is important for living systems.
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18 Molecules Molecules important to life consist of inorganic and organic substances. Inorganic – either C or H maybe present (e,g, CO 2, H 2 ) Organic- C and H (hydrocarbons) are present (e.g. CH 3 )
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19 Organic Molecules Carbon, a tetravalent atom, is an ideal element for life because it serves as the skeleton for macromolecules. Functional groups (R) attached to these carbons confer unique properties to these macromolecules.
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20 Macromolecules Carbohydrates Lipids Proteins Nucleic acids
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21 Carbohydrates Simple Sugars Disaccharides Polysaccharides
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22 Classes of Carbohydrates Major sugars (monosaccharides) in the cell are glucose, galactose and fructose. Several sugars bonded together are called polysaccharides.
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23 Glycosidic Bond Sugars are bonded by special kind of covalent linkage called glycosidic bonds. Water is released (dehydration) after the bond is formed.
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24 Polysaccharides Peptidoglycan in bacteria is an example of a polysaccharide.
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25 Lipids Fats Phospholipids Steroids
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26 Fats Synthesis and structure of a triglyceride (fat), a storage molecule.
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27 Phospholipids Phospholipids serve as a major structural component of cell membranes. It is an amphiphatic molecule. Its phosphate “head” is hydrophilic and its fatty acid “tail” is hydrophobic.
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28 Cholesterol: An Alcoholic Steroid Cholesterols are associated with cell membranes of some cells such as those of eukaryotes.
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29 Proteins Proteins are the predominant organic molecules in cells. Proteins consist of a series of amino acids (e.g. peptides, polypeptides) Peptide bonds link amino acids together. Examples: hormones, enzymes, antibodies, etc.
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30 Amino Acids An amino acid has a central carbon, to which carboxylic, amino and R groups are attached. Amino acid types vary according to the reactive (R) groups present.
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31 The 20 Naturally Occurring Amino Acids
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32. A peptide bond (covalent) forms between the amino group on one amino acid and the carboxyl group on another amino acid with the accompanying loss of water. Peptide Bond
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33 Levels of Structures of Protein Proteins take on a variety of shapes due to extensive folding of the molecule. This enable them to perform specific functions and interactions with other molecules.
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34 Nucleic acids Deoxyribonucleic acid (DNA) Ribonucleic acid (RNA) DNA contains genetic information and transfers it to RNA RNA translates the DNA information into proteins
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35 Nucleic Acid Polymers Nucleic acids are polymers of repeating units called nucleotides.
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36 The Sugars and Nitrogenous Bases The pentose sugars and nitrogen bases determine whether a molecule will be DNA or RNA.
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37. The DNA configuration is a double helix similar to “a spiral staircase” Sugar and phosphate backbones are held together by hydrogen bonds formed between nitrogenous bases. The DNA Molecule
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38 DNA : The Molecule of Inheritance DNA serves as a template for the synthesis of new DNA strands as well as mRNA, tRNA and rRNA. DNA replication is an important step in cell reproduction.
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39 The Cell Fundamental characteristics shared by all living organisms: Reproduction Metabolism Motility (Response to molecules) Protection and Storage (Cell wall or membrane) Nutrient transport
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