Chapter 2: The Chemistry of Microbiology – Basic Fundamentals of Chemistry

Chapter 2: The Chemistry of Microbiology – Basic Fundamentals of Chemistry

Introduction

This chapter introduces the essential chemical principles underlying microbiology. Understanding the structure of matter, chemical bonds, and the properties of biological macromolecules is fundamental for studying microbial life and its processes.

Basic Chemical Concepts

Elements and Atoms

• Element: A pure substance consisting of only one type of atom. Examples: Hydrogen (H), Oxygen (O), Carbon (C).

• Atom: The smallest unit of an element that retains its chemical properties.

• Matter: Anything that occupies space and has mass.

Subatomic Particles

• Protons: Positively charged particles found in the nucleus.

• Neutrons: Neutral particles found in the nucleus.

• Electrons: Negatively charged particles orbiting the nucleus in electron shells.

Atomic Number and Mass

• Atomic Number: Number of protons in an atom; defines the element.

• Atomic Mass: Sum of protons and neutrons in the nucleus.

Isotopes and Radioactivity

• Isotopes: Atoms of the same element with different numbers of neutrons.

• Radioactive Decay: The process by which unstable isotopes lose energy by emitting radiation.

Electron Configuration

• Electron Shells: Energy levels where electrons are found. The first shell holds up to 2 electrons; the second up to 8, etc.

• Valence Electrons: Electrons in the outermost shell; determine chemical reactivity.

• Electronegativity: The ability of an atom to attract electrons in a chemical bond.

Example: An atom with 6 electrons (e.g., carbon) has 2 electrons in the inner shell and 4 in the valence shell.

Common Elements in Living Organisms

• C, H, O, N, P, S: Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorus, and Sulfur are the most common elements in biological molecules.

Chemical Bonds

Types of Chemical Bonds

• Covalent Bonds: Atoms share electrons. Can be polar (unequal sharing) or non-polar (equal sharing).

• Ionic Bonds: Formed when electrons are transferred from one atom to another, creating charged ions.

• Hydrogen Bonds: Weak attractions between a hydrogen atom (covalently bonded to O or N) and another electronegative atom.

Charged Atoms: Atoms that gain or lose electrons become ions. Cations are positively charged; anions are negatively charged.

Bond Strength

• Covalent Bonds: Strongest

• Ionic Bonds: Moderate (weaker in aqueous solutions)

• Hydrogen Bonds: Weakest

Chemical Reactions

Types of Chemical Reactions

• Synthesis Reactions (Anabolism): Building larger molecules from smaller ones. Usually require energy input (endothermic).

• Decomposition Reactions (Catabolism): Breaking down molecules into smaller units. Usually release energy (exothermic).

• Exchange (Transfer) Reactions: Atoms are exchanged between molecules.

Parts of a Chemical Reaction

• Reactants: Substances that start a reaction.

• Products: Substances formed by the reaction.

• Enzymes: Biological catalysts that speed up reactions.

• Indicators: Substances that show the progress or completion of a reaction (e.g., color change).

Energy in Reactions

• Endothermic: Absorb energy.

• Exothermic: Release energy.

Inorganic vs. Organic Molecules

• Inorganic Molecules: Usually do not contain C-H bonds (e.g., water, salts, acids, bases).

• Organic Molecules: Contain C-H bonds (e.g., carbohydrates, proteins, lipids, nucleic acids).

Water, Acids, Bases, and Salts

• Water: Universal solvent, polar molecule, forms hydrogen bonds.

• Acids: Release H+ ions in solution; pH < 7.

• Bases: Accept H+ ions or release OH-; pH > 7.

• Salts: Compounds formed from the reaction of acids and bases; dissociate into ions in water.

• pH Scale: Measures hydrogen ion concentration; ranges from 0 (acidic) to 14 (basic), with 7 as neutral.

Substance	pH Value
Stomach Acid	1-2
Pure Water	7
Household Ammonia	11-12

Macromolecules and Biological Molecules

Macromolecules and Macronutrients

• Macromolecules: Large, complex molecules essential for life (carbohydrates, lipids, proteins, nucleic acids).

• Macronutrients: Nutrients required in large amounts (C, H, O, N, P, S).

Monomers and Polymers

• Monomer: Small, repeating unit that forms polymers.

• Polymer: Large molecule made of monomers.

• Dehydration Synthesis: Forms polymers by removing water; endothermic.

• Hydrolysis: Breaks polymers into monomers by adding water; exothermic.

Four Classes of Biological Molecules

1. Carbohydrates

• Monosaccharides: Simple sugars (e.g., glucose).

• Disaccharides: Two monosaccharides joined (e.g., sucrose).

• Polysaccharides: Many monosaccharides (e.g., starch, cellulose).

• Function: Energy storage, structural support.

2. Lipids

• Hydrophobic: Repel water.

• Hydrophilic: Attract water.

• Simple Lipids: Fats and oils; composed of glycerol and fatty acids.

• Phospholipids: Major component of cell membranes; have hydrophilic heads and hydrophobic tails.

• Steroids: Four fused carbon rings (e.g., cholesterol).

• Waxes: Long-chain fatty acids bonded to alcohols.

• Saturated: No double bonds in fatty acids; solid at room temperature.

• Unsaturated: One or more double bonds; liquid at room temperature.

3. Proteins

• Amino Acids: Monomers of proteins; 20 standard types.

• Peptide Bond: Covalent bond linking amino acids.

• Protein Structure: Primary (sequence), secondary (alpha-helix, beta-sheet), tertiary (3D folding), quaternary (multiple polypeptides).

• Enzymes: Proteins that catalyze biochemical reactions.

• Function: Structure, transport, catalysis, regulation.

4. Nucleic Acids

• Nucleotides: Monomers of nucleic acids; consist of a sugar, phosphate, and nitrogenous base.

• DNA: Deoxyribonucleic acid; stores genetic information.

• RNA: Ribonucleic acid; involved in protein synthesis.

• ATP: Adenosine triphosphate; main energy currency of the cell.

Functional Groups and R-Groups

• Functional Group: Specific group of atoms within molecules responsible for characteristic reactions (e.g., hydroxyl, carboxyl, amino).

• R-Group: Side chain in amino acids that determines their properties.

Summary Table: Comparison of Biological Macromolecules

Macromolecule	Elements	Monomer	Bond Type	Function
Carbohydrates	C, H, O	Monosaccharide	Glycosidic	Energy, structure
Lipids	C, H, O (sometimes P)	Fatty acids, glycerol	Ester	Membranes, energy storage
Proteins	C, H, O, N, (S)	Amino acid	Peptide	Catalysis, structure, transport
Nucleic Acids	C, H, O, N, P	Nucleotide	Phosphodiester	Genetic information

Additional info:

• Buffers: Substances that help maintain a stable pH in biological systems.

• Metabolism: The sum of all chemical reactions in a cell, including anabolism (building up) and catabolism (breaking down).