Chemistry of Microbes
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Transcript of Chemistry of Microbes
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Chemistry of Microbes
LECTURES IN MICROBIOLOGY
LESSON 2
Sofronio AgustinProfessor
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Topics
Fundamental Building Blocks
Macromolecules
The Cell
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Fundamental Building Blocks
Atoms
Elements Molecules and compounds
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Atoms
Subatomic ParticlesProton = positive chargeNeutron = neutralElectron = negative charge
Atomic number = no. of protons Atomic mass = no. of protons and neutrons
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5Models of Atomic Structure
Atomic Structure
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Isotopes
Atoms 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.
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Major Elements of Life
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Molecules and Compounds
Molecule = 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
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Chemical Bonds
Covalent
Ionic Hydrogen
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Chemical Bonds
Chemical bonds involve atoms sharing, donating or accepting electrons
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Covalent Bonding
Examples of covalent bonding
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Polar Covalent Bond
Polarity 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.
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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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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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Hydrogen Bond
Hydrogen 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
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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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The pH Scale
The pH of an environment (exterior or interior of a cell) is important for living systems.
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Molecules
Molecules 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)
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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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Macromolecules
Carbohydrates Lipids Proteins Nucleic acids
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Carbohydrates
Simple Sugars
Disaccharides
Polysaccharides
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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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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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Polysaccharides
Peptidoglycan in bacteria is an example of a polysaccharide.
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Lipids
Fats Phospholipids
Steroids
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Fats
Synthesis and structure of a triglyceride (fat), a storage molecule.
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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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Cholesterol: An Alcoholic Steroid
Cholesterols are associated with cell membranes of some cells such as those of eukaryotes.
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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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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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The 20 Naturally Occurring Amino Acids
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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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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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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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Nucleic Acid Polymers
Nucleic acids are polymers of repeating units called nucleotides.
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The Sugars and Nitrogenous Bases
The pentose sugars and nitrogen bases determine whether a molecule will be DNA or RNA.
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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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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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The Cell
Fundamental characteristics shared by all living organisms: Reproduction Metabolism Motility (Response to molecules) Protection and Storage (Cell wall or
membrane) Nutrient transport