Microbiology Exam Study Guide: Chapters 1–3 (Introduction, Chemistry of Biology, Prokaryotic Cells, Eukaryotes)

Chapter 1: Introduction to Microbiology

A Brief History of Microbiology

This section covers the foundational figures and concepts in microbiology, as well as the development of the scientific method and key postulates.

• Key Historical Figures: Louis Pasteur, Joseph Lister, Antonie van Leeuwenhoek, Robert Koch, Francisco Redi are considered pioneers in microbiology for their discoveries in germ theory, aseptic technique, and the identification of microorganisms.

• Scientific Method: A systematic approach to research involving observation, hypothesis formation, experimentation, and conclusion. It is essential for validating scientific theories.

• Koch’s Postulates: A set of criteria to establish a causative relationship between a microbe and a disease. Important for identifying pathogens.

• Biogenesis vs. Germ Theory: Biogenesis is the principle that living organisms arise from pre-existing life, while germ theory states that specific diseases are caused by specific microorganisms.

• Microorganisms: Organisms too small to be seen with the naked eye, including bacteria, viruses, fungi, protozoa, and algae.

• Pathogen vs. Opportunistic Pathogen: Pathogens cause disease in healthy hosts, while opportunistic pathogens cause disease primarily in immunocompromised individuals.

Classifying Microbes and Their Interactions

Microorganisms are classified based on their structure, function, and genetic relationships. Understanding these classifications helps in identifying and studying microbes.

• Taxonomy: The science of classifying organisms. Taxonomic ranks include domain, kingdom, phylum, class, order, family, genus, and species.

• Species Concept: Microbial species are often defined by genetic similarity and ability to interbreed (for sexually reproducing organisms).

• Prokaryotes vs. Eukaryotes: Prokaryotes (bacteria and archaea) lack a nucleus and membrane-bound organelles, while eukaryotes (fungi, protozoa, algae, plants, animals) have these structures.

• Domains and Kingdoms: The three domains are Bacteria, Archaea, and Eukarya. The five-kingdom system includes Monera, Protista, Fungi, Plantae, and Animalia.

• Pathogenicity: The ability of a microorganism to cause disease. Pathogens differ in their mechanisms of infection and virulence.

Chapter 2: Chemistry of Biology

From Atoms to Macromolecules

This section introduces the chemical basis of life, including atomic structure, elements, and the formation of biological macromolecules.

• Element: A substance that cannot be broken down into simpler substances by chemical means. The smallest unit is the atom.

• Atomic Structure: Atoms consist of protons, neutrons, and electrons. The atomic number is the number of protons.

• Periodic Table: Organizes elements by increasing atomic number and similar chemical properties.

• Molecules and Compounds: Atoms combine via chemical bonds (ionic, covalent, hydrogen) to form molecules and compounds.

• pH and Solutions: pH measures the concentration of hydrogen ions ($pH = -\log[H^+]$). Acids have pH < 7, bases have pH > 7.

Chemical Bonds and Basic Compounds

• Chemical Bond: The force holding atoms together in molecules. Types include ionic, covalent, and hydrogen bonds.

• Dehydration Synthesis: A reaction that joins two molecules by removing water.

• Hydrolysis: A reaction that breaks a bond by adding water.

• Exergonic vs. Endergonic Reactions: Exergonic reactions release energy; endergonic reactions require energy input.

Biologically Important Macromolecules

• Macromolecules: Large molecules essential for life, including carbohydrates, proteins, lipids, and nucleic acids.

• Monomers and Polymers: Monomers are building blocks; polymers are chains of monomers.

• Proteins: Made of amino acids; structure includes primary, secondary, tertiary, and quaternary levels. Hydrogen bonds stabilize secondary structure.

• Nucleic Acids: DNA and RNA are polymers of nucleotides. DNA stores genetic information; RNA is involved in protein synthesis.

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

Chapter 3: Introduction to Prokaryotic Cells

Prokaryotic Cell Basics

Prokaryotic cells are structurally simpler than eukaryotic cells and lack a nucleus. This section covers their basic features and diversity.

• Prokaryotic vs. Eukaryotic Cells: Prokaryotes lack a nucleus and membrane-bound organelles; eukaryotes possess both.

• Shapes of Bacteria: Common shapes include cocci (spherical), bacilli (rod-shaped), and spirilla (spiral).

• Bacterial Arrangements: Bacteria may form chains, clusters, or pairs depending on their division patterns.

• Reproduction: Most prokaryotes reproduce by binary fission, a form of asexual reproduction.

• Genetic Exchange: Includes conjugation (direct transfer of DNA), transformation (uptake of free DNA), and transduction (transfer by viruses).

Extracellular Structures

• Cell Wall: Provides shape and protection. Bacterial cell walls contain peptidoglycan; Gram-positive and Gram-negative bacteria differ in wall structure.

• Glycocalyx: A protective layer outside the cell wall; can be a capsule (organized) or slime layer (loose).

• Flagella: Used for motility; arrangement and structure differ between prokaryotes and eukaryotes.

• Pili and Fimbriae: Hair-like structures for attachment and genetic exchange.

Intracellular Structures

• Cytoplasm: Gel-like substance inside the cell containing enzymes, nutrients, and genetic material.

• Nucleoid: Region containing the bacterial chromosome (DNA).

• Plasmids: Small, circular DNA molecules that can carry antibiotic resistance genes.

• Inclusion Bodies: Storage sites for nutrients and other substances.

• Endospores: Highly resistant structures formed by some bacteria for survival in harsh conditions.

Classification of Eukaryotes

Overview of Eukaryotes and Endosymbiosis

• Endosymbiosis: Theory that eukaryotic organelles (mitochondria, chloroplasts) originated from symbiotic prokaryotes.

• Evidence: Mitochondria and chloroplasts have their own DNA and double membranes, supporting the endosymbiotic theory.

Classification of Eukaryotes

• Kingdoms: Eukaryotes are classified into kingdoms such as Protista, Fungi, Plantae, and Animalia.

• Fungi: Heterotrophic organisms that absorb nutrients; reproduce by spores.

• Protozoa: Unicellular eukaryotes; classified by movement (flagella, cilia, pseudopodia).

• Algae: Photosynthetic eukaryotes; can be unicellular or multicellular.

• Helminths: Parasitic worms; include flatworms and roundworms.

Extracellular and Intracellular Structures of Eukaryotic Cells

• Cell Wall and Membrane: Plants and fungi have cell walls; animals do not.

• Flagella and Cilia: Used for movement; structurally different from prokaryotic flagella.

• Organelles: Eukaryotic cells contain membrane-bound organelles such as nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, lysosomes, and chloroplasts (in plants and algae).

• Ribosomes: Sites of protein synthesis; eukaryotic ribosomes are larger (80S) than prokaryotic (70S).

Table: Comparison of Prokaryotic and Eukaryotic Cells

Feature	Prokaryotic Cells	Eukaryotic Cells
Nucleus	Absent	Present
Membrane-bound Organelles	Absent	Present
Cell Wall	Usually present (peptidoglycan)	Present in plants/fungi (cellulose/chitin), absent in animals
Ribosome Size	70S	80S
Reproduction	Binary fission	Mitosis/meiosis

Additional info:

• Review learning objectives and chapter summaries for each chapter.

• Practice answering reflection and end-of-chapter questions to reinforce understanding.