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Chemistry of MicrobesChemistry of Microbes
LECTURES IN
MICROBIOLOGY
LECTURES IN
MICROBIOLOGY
LESSON 2LESSON 2
Sofronio Agustin
Professor
Sofronio Agustin
Professor
2
TopicsTopics
Fundamental Building Blocks
Macromolecules
The Cell
3
Fundamental Building BlocksFundamental Building Blocks
Atoms
Elements
Molecules and compounds
4
AtomsAtoms
Subatomic Particles
Proton = positive charge
Neutron = neutral
Electron = negative charge
Atomic number = no. of protons Atomic mass = no. of protons and neutrons
5Models of Atomic Structure
Atomic StructureAtomic Structure
6
IsotopesIsotopes
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.
7
Major Elements of Life Major Elements of Life
8
Molecules and CompoundsMolecules 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
9
Chemical BondsChemical Bonds
Covalent
Ionic
Hydrogen
10
Chemical BondsChemical Bonds
Chemical bonds involve atoms sharing, donating or accepting electrons
11
Covalent BondingCovalent Bonding
Examples of covalent bonding
12
Polar Covalent BondPolar 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.
13
Ionic BondingIonic Bonding
Sodium chloride
(table salt) is an
example of ionic
bonding, that is,
electron transfer
among atoms or
redox reaction.
14
IonizationIonization
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.
15
Hydrogen BondHydrogen 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
16
pHpH
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
17
The pH ScaleThe pH Scale
The pH of an environment (exterior or interior of a cell) is important for living systems.
18
MoleculesMolecules
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)
19
Organic Molecules 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.
20
MacromoleculesMacromolecules
Carbohydrates Lipids Proteins Nucleic acids
21
CarbohydratesCarbohydrates
Simple Sugars
Disaccharides
Polysaccharides
22
Classes of CarbohydratesClasses of Carbohydrates
Major sugars (monosaccharides) in the cell are glucose, galactose and fructose.
Several sugars bonded together are called polysaccharides.
23
Glycosidic BondGlycosidic Bond
Sugars are bonded by special kind of covalent linkage called glycosidic bonds.
Water is released
(dehydration) after
the bond is formed.
24
PolysaccharidesPolysaccharides
Peptidoglycan in bacteria is an example of a polysaccharide.
25
LipidsLipids
Fats
Phospholipids
Steroids
26
FatsFats
Synthesis and structure of a triglyceride (fat), a storage molecule.
27
PhospholipidsPhospholipids
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.
28
Cholesterol: An Alcoholic SteroidCholesterol: An Alcoholic Steroid
Cholesterols are associated with cell membranes of some cells such as those of eukaryotes.
29
ProteinsProteins
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.
30
Amino AcidsAmino 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.
31
The 20 Naturally Occurring Amino Acids The 20 Naturally Occurring Amino Acids
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 Peptide Bond
33
Levels of Structures of ProteinLevels 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.
34
Nucleic acidsNucleic acids
Deoxyribonucleic acid (DNA) Ribonucleic acid (RNA) DNA contains genetic information and
transfers it to RNA RNA translates the DNA information into
proteins
35
Nucleic Acid PolymersNucleic Acid Polymers
Nucleic acids are polymers of repeating units called nucleotides.
36
The Sugars and Nitrogenous BasesThe Sugars and Nitrogenous Bases
The pentose sugars and nitrogen bases determine whether a molecule will be DNA or RNA.
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 MoleculeThe DNA Molecule
38
DNA : The Molecule of InheritanceDNA : 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.
39
The CellThe 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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