Microbiology Exam Study Guide: Key Concepts and Review Questions

Study Guide - Smart Notes

Tailored notes based on your materials, expanded with key definitions, examples, and context.

Microbiology Exam Study Guide

Overview

This study guide covers foundational concepts in microbiology, including microbial classification, cell structure, microscopy, genetics, and laboratory techniques. The questions are designed to test understanding of key principles and applications relevant to a college-level microbiology course.

Classification and Types of Microorganisms

Definitions and Key Terms

Virus: A non-cellular infectious agent that requires a host cell to replicate.
Pathogen: Any microorganism capable of causing disease.
Infection: The invasion and multiplication of microorganisms in body tissues.
Microbe: A microscopic organism, which may be a bacterium, virus, fungus, or protozoan.
Bacterium: A single-celled prokaryotic microorganism.

Taxonomy and Classification

Taxonomy: The science of classifying organisms.
Binomial Nomenclature: The formal system for naming species using two names: genus and species (e.g., Escherichia coli).
Hierarchy: Domain > Kingdom > Phylum > Class > Order > Family > Genus > Species.

Cell Structure and Morphology

Prokaryotic vs. Eukaryotic Cells

Prokaryotic Cells: Lack a nucleus and membrane-bound organelles; include bacteria and archaea.
Eukaryotic Cells: Have a nucleus and membrane-bound organelles; include fungi, protozoa, algae, and animals.

Cell Morphologies

Coccus: Spherical-shaped bacteria.
Bacillus: Rod-shaped bacteria.
Spirillum: Spiral-shaped bacteria.
Vibrio: Comma-shaped bacteria.
Spirochete: Flexible, spiral-shaped bacteria.

Example: Staphylococcus aureus (coccus), Bacillus subtilis (bacillus).

Cellular Structures

Cell Membrane: Phospholipid bilayer controlling entry and exit of substances.
Cell Wall: Provides structural support; composed of peptidoglycan in bacteria.
Flagella: Structures for motility.
Pili/Fimbriae: Structures for attachment.
Capsule: Protective outer layer in some bacteria.

Microbial Motility and Structures

Protozoan Motility: Achieved via flagella, cilia, or pseudopodia.
Archaea vs. Bacteria: Differ in cell wall composition, membrane lipids, and genetic machinery.

History and Discovery in Microbiology

Antonie van Leeuwenhoek: First to observe microorganisms using a microscope.
Edward Jenner: Developed the first vaccine (smallpox).
Penicillin: Discovered by Alexander Fleming.
Recombinant DNA: Technology for combining DNA from different organisms.

Microscopy and Staining

Types of Microscopes

Light Microscope: Uses visible light to observe specimens.
Electron Microscope: Uses electron beams for higher resolution imaging.
Phase-Contrast Microscope: Enhances contrast in transparent specimens.
Fluorescence Microscope: Uses fluorescent dyes to visualize structures.

Microscope Parts and Functions

Ocular Lens (Eyepiece): Magnifies the image.
Objective Lens: Provides primary magnification.
Stage: Holds the specimen slide.
Condenser: Focuses light on the specimen.
Coarse/Fine Focus: Adjusts the focus of the image.

Staining Techniques

Gram Stain: Differentiates bacteria into Gram-positive (purple) and Gram-negative (pink) based on cell wall structure.
Acid-Fast Stain: Identifies mycobacteria.
Simple Stain: Uses a single dye to color cells.
Negative Stain: Stains the background, leaving cells unstained.

Genetics and Molecular Biology

DNA, RNA, and Protein Synthesis

DNA: Double-stranded molecule carrying genetic information.
RNA: Single-stranded molecule involved in protein synthesis.
mRNA Codons: Triplets of nucleotides coding for amino acids.
Mutation: A change in the DNA sequence.
Base Substitution: Replacement of one nucleotide with another.
Frameshift Mutation: Insertion or deletion of nucleotides altering the reading frame.

Codon	Amino Acid	Type
UUA	leucine	nonsense
GCA	alanine
AUG	lysine	asparagine
GUU	valine	UCG, serine
Additional info:	Codons are three-nucleotide sequences on mRNA that specify amino acids during translation.

Cellular Processes and Structures

Photosynthetic Pigments: Molecules that absorb light for photosynthesis (e.g., chlorophyll).
Cell Membrane: Selectively permeable barrier composed of a phospholipid bilayer.
Cell Wall: Provides shape and protection; composition varies among bacteria, archaea, and eukaryotes.
Ribosomes: Sites of protein synthesis; size differs between prokaryotes (70S) and eukaryotes (80S).

Laboratory Techniques and Applications

Culture Media: Nutrient solutions used to grow microorganisms in the lab.
Streak Plate Method: Technique to isolate pure bacterial colonies.
Gram Stain Steps: Crystal violet, iodine, alcohol decolorization, safranin counterstain.
Microscopy Techniques: Oil immersion increases resolution; phase-contrast enhances visualization of live cells.

Viruses and Prions

Virus: Acellular infectious agent with DNA or RNA genome.
Prion: Infectious protein causing neurodegenerative diseases.
Difference: Viruses contain nucleic acids; prions are only proteins.

Additional Key Concepts

Endospores: Dormant, resistant structures formed by some bacteria (e.g., Bacillus species) for survival in harsh conditions.
Antibiotics: Substances that inhibit or kill microorganisms; e.g., penicillin inhibits cell wall synthesis.
Pathogenicity: The ability of a microorganism to cause disease.

Summary Table: Prokaryotes vs. Eukaryotes

Feature	Prokaryotes	Eukaryotes
Nucleus	No	Yes
Organelles	No	Yes
Cell Wall	Peptidoglycan (bacteria)	Cellulose (plants), chitin (fungi), or absent
Ribosome Size	70S	80S
Examples	Bacteria, Archaea	Fungi, Protozoa, Algae, Animals

Sample Equations and Formulas

Magnification:

DNA to mRNA Transcription:

Mutation Rate:

Conclusion

This guide summarizes the essential topics and concepts for a microbiology exam, including microbial classification, cell structure, microscopy, genetics, and laboratory techniques. Mastery of these topics is crucial for understanding the diversity and function of microorganisms in health, disease, and the environment.