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

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Fundamental Building BlocksFundamental Building Blocks

Atoms

Elements

Molecules and compounds

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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

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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.

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Major Elements of Life Major Elements of Life

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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

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Chemical BondsChemical Bonds

Covalent

Ionic

Hydrogen

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Chemical BondsChemical Bonds

Chemical bonds involve atoms sharing, donating or accepting electrons

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Covalent BondingCovalent Bonding

Examples of covalent bonding

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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.

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Ionic BondingIonic Bonding

Sodium chloride

(table salt) is an

example of ionic

bonding, that is,

electron transfer

among atoms or

redox reaction.

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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.

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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

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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

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The pH ScaleThe pH Scale

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

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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)

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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.

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MacromoleculesMacromolecules

Carbohydrates Lipids Proteins Nucleic acids

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CarbohydratesCarbohydrates

Simple Sugars

Disaccharides

Polysaccharides

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Classes of CarbohydratesClasses 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 BondGlycosidic 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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PolysaccharidesPolysaccharides

Peptidoglycan in bacteria is an example of a polysaccharide.

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LipidsLipids

Fats

Phospholipids

Steroids

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FatsFats

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

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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.

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Cholesterol: An Alcoholic SteroidCholesterol: An Alcoholic Steroid

Cholesterols are associated with cell membranes of some cells such as those of eukaryotes.

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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.

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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.

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The 20 Naturally Occurring Amino Acids 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 Peptide Bond

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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.

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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

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Nucleic Acid PolymersNucleic Acid Polymers

Nucleic acids are polymers of repeating units called nucleotides.

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The Sugars and Nitrogenous BasesThe 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 MoleculeThe DNA Molecule

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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.

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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