Chemistry of Microbes

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LECTURES IN MICROBIOLOGY. Chemistry of Microbes. LESSON 2. Sofronio Agustin Professor. Topics. Fundamental Building Blocks Macromolecules The Cell. Fundamental Building Blocks. Atoms Elements Molecules and compounds. Atoms. Subatomic Particles Proton = positive charge - PowerPoint PPT Presentation


  • Chemistry of MicrobesLESSON 2LECTURES IN MICROBIOLOGYSofronio AgustinProfessor

  • Topics

    Fundamental Building BlocksMacromoleculesThe Cell

  • Fundamental Building BlocksAtomsElementsMolecules and compounds

  • AtomsSubatomic ParticlesProton = positive chargeNeutron = neutralElectron = negative chargeAtomic number = no. of protons Atomic mass = no. of protons and neutrons

  • Models of Atomic StructureAtomic Structure

  • IsotopesAtoms with same number of protons but differ in number of neutrons are called isotopes.Example: 12C, 13C, and 14C are isotopes of carbon.Radioisotopes emit radiation in the form of alpha or beta or gamma rays or photons.

  • Major Elements of Life

  • Molecules and CompoundsMolecule = combination of two or more elements (e.g.H2)Compound = combination of two or more different elements (e.g. H2O) Molecules are held together by chemical bonds

  • Chemical BondsCovalentIonicHydrogen

  • Chemical BondsChemical bonds involve atoms sharing, donating or accepting electrons

  • Covalent BondingExamples of covalent bonding

  • Polar Covalent BondPolarity occurs when atoms electrons unequally due to differences in electronegativities. This is seen in water (H2O).

    More electronegative atoms tend to pull electrons toward them creating a polar molecule.

  • Ionic BondingSodium chloride (table salt) is an example of ionic bonding, that is, electron transfer among atoms or redox reaction.

  • IonizationMolecules 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.

  • Hydrogen BondHydrogen bonding is formed between the partially positive (hydrogen) end of a polar molecule and the negative end of another (e.g. O2 or N2).

    Example : Water molecules

  • pHpH measurement of the H+ ion concentration in a solution.General rule: Acidic = excess H+ ions in solutionBasic = excess OH- ions in solutionNeutral = equal amounts of H+ and OH- ions

  • The pH ScaleThe pH of an environment (exterior or interior of a cell) is important for living systems.

  • MoleculesMolecules important to life consist of inorganic and organic substances.

    Inorganic either C or H maybe present (e,g, CO2, H2)Organic- C and H (hydrocarbons) are present (e.g. CH3)

  • 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.

  • MacromoleculesCarbohydratesLipidsProteinsNucleic acids

  • CarbohydratesSimple SugarsDisaccharides


  • Classes of CarbohydratesMajor sugars (monosaccharides) in the cell are glucose, galactose and fructose. Several sugars bonded together are called polysaccharides.

  • Glycosidic BondSugars are bonded by special kind of covalent linkage called glycosidic bonds.

    Water is released (dehydration) after the bond is formed.

  • PolysaccharidesPeptidoglycan in bacteria is an example of a polysaccharide.

  • LipidsFatsPhospholipidsSteroids

  • FatsSynthesis and structure of a triglyceride (fat), a storage molecule.

  • PhospholipidsPhospholipids 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.

  • Cholesterol: An Alcoholic SteroidCholesterols are associated with cell membranes of some cells such as those of eukaryotes.

  • ProteinsProteins 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.

  • 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.

  • The 20 Naturally Occurring Amino Acids

  • .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

  • Levels of Structures of ProteinProteins 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.

  • Nucleic acidsDeoxyribonucleic acid (DNA)Ribonucleic acid (RNA)DNA contains genetic information and transfers it to RNARNA translates the DNA information into proteins

  • Nucleic Acid PolymersNucleic acids are polymers of repeating units called nucleotides.

  • The Sugars and Nitrogenous BasesThe pentose sugars and nitrogen bases determine whether a molecule will be DNA or RNA.

  • . 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

  • DNA : The Molecule of InheritanceDNA 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.

  • The CellFundamental characteristics shared by all living organisms:ReproductionMetabolismMotility (Response to molecules)Protection and Storage (Cell wall or membrane) Nutrient transport