Download Microbiology: A Systems Approach

LECTURES IN
MICROBIOLOGY
Chemistry of Microbes
LESSON 2
Sofronio Agustin
Professor
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 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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Atomic Structure
Models of 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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.
Peptide Bond
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.
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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 Molecule
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.
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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
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