micro chap 1.

Basic Biology Review

  • Biology is the study of life

  • All organisms are composed of at least one cell

  • The cell is the most basic unit of life

  • All cells come from pre-existing cells

  • In a multicellular organism:

    • Specialized cells are present

    • Cells work together (integrated cellular activity)

  • A review of basic biology is on Canvas if you need to review it

  • LUCA (last universal common ancestor)

  • Supergroups of Domain Eukarya

Taxonomy and Nomenclature

  • Proper Taxonomy (Genus species)

  • Latinized names are used so that they are universal among people of all languages

  • Italicized when typed; Underlined when written

    • Listeria monocytogenes

  • Some names may be descriptive:

    • Staphylococcus aureus tells you that the cells are round and in clusters and aureus means gold

    • Colonies of this bacteria may be a bright gold

  • Some names may honor a scientist:

    • Escherichia coli honors the scientist Theodor Escherich and coli tells you its usual location in the body

Cellular and Acellular Entities

  • Cellular types:

    • Prokaryotes – Unicellular, lack nuclei and membrane-bound organelles

    • Eukaryotes – Uni or multicellular, have a nucleus and membrane-bound organelles

  • Acellular types:

    • Viruses – Parasitic particles comprised of nucleic acid and protein

    • Prions – Misfolded protein whose extracellular form does not contain nucleic acid

  • Cell components and examples (from diagrams/text):

    • Cell membrane, Nucleus, Mitochondria, Ribosomes

    • Cell membrane, Cell wall, Flagellum

    • Flagellum (note: singular/plural in diagrams)

    • Chromosome, Prokaryotic, Eukaryotic

    • Capsid, Envelope, AIDS virus, Bacteriophage, Nucleic acid, Ribosomes

  • Virus and Prion (acellular types) and their basic concepts

  • Microbiology is the study of organisms too small to be seen by the naked eye

  • Organism groups typically studied:

    • Bacteria / Archaea, Fungi, Algae (photosynthetic protists), Viruses, Protists, Helminths

Importance of Microorganisms

  • Decompose organic waste

  • Are producers in the ecosystem by photosynthesis

  • Produce industrial chemicals such as ethyl alcohol and acetone

  • Produce fermented foods such as vinegar, cheese, and bread

  • Cause disease in other organisms

Knowledge of Microorganisms and Practical Relevance

  • Allows humans to:

    • Prevent food spoilage

    • Prevent disease occurrence

  • Led to aseptic techniques to prevent contamination in medicine and in microbiology laboratories

Size, Scale, and Diffusion in Microbes

  • How small are microbes?

    • One human cell

    • One bacterium

    • One virus particle

  • A review of metric conversions is on Canvas if you need to review it

  • The importance of being small:

    • Smaller cells, like prokaryotes, have a larger Surface area-to-Volume ratio

    • Large ratio: Nutrients can easily and rapidly reach any part of the interior cell (more diffusion)

    • Small ratio: Nutrients cannot easily and rapidly reach any part of the interior cell

  • Plasma membrane of cell

  • As organisms become bigger it becomes more difficult for them to exchange materials with their surroundings

  • Quantitative note on surface area to volume for spheres (example):

    • For a sphere with radius rr, the surface area is SA=4πr2SA = 4\pi r^2 and the volume is V=43πr3V = \frac{4}{3}\pi r^3

    • Hence the surface-area-to-volume ratio is SAV=3r\frac{SA}{V} = \frac{3}{r}

Brief History of Life on Earth and the Role of Microorganisms

  • Abiotic synthesis of monomers (to make macromolecules)

Abiotic Synthesis and the Miller–Urey Experiments (Page 4)

  • The Stanley Miller–Harold Urey Experiment showed abiotic synthesis of organic monomers

    • Amino Acids (Proteins)

    • Nucleotides & Nucleic Acids

  • Evidence for the RNA World:

    • Life is defined partly by the process of inheritance, which is based on self-replicating molecules

    • One hypothesis is that the first genes were short strands of RNA that replicated themselves without the assistance of proteins, perhaps using RNAs that can act as enzymes, called ribozymes

  • Inorganic compounds

  • Abiotic synthesis of organic monomers

  • Abiotic synthesis of polymers

  • Formation of pre-cells

  • Self-replicating molecules

  • Membrane-enclosed compartment

  • Complementary chain

  • Polymer

  • Organic monomers

  • Monomers will combine into polymerize such as proteins and nucleic acids, by dripping solutions of organic monomers onto hot sand or clay or rock

  • Abiotically created molecules will aggregate within a membrane

  • Miller–Urey Experiment (1950s)

  • Life is defined partly by its perpetuation through reproduction; short strands of RNA that replicated themselves without the assistance of proteins may have been the first genes

Cyanobacteria and Oxygenation

  • Cyanobacteria is a photosynthetic prokaryote

  • It is because of cyanobacteria that our atmosphere is oxygenic

  • Vegetative cells which carry out photosynthesis

  • Cyanobacteria

  • Some cyanobacteria have heterocysts which fix nitrogen gas to organic nitrogen

The Oxygen Revolution and Timeline

  • “Oxygen revolution” timeline (billions of years ago): 4, 3, 2, 1, 0

  • Axis labels show a logarithmic scale of Atmospheric O2 (percent of present-day levels; log scale)

  • The chart indicates that:

    • Anaerobic organisms were predominant early

    • Aerobic organisms were predominant later

The Endosymbiotic Theory

  • The eukaryotic cell evolved from the engulfment of prokaryotic cells

  • Formation of the nucleus

  • Engulf aerobic bacterium → mitochondria

  • Engulf photosynthetic prokaryote → chloroplast

Notes and connections

  • LUCA and early life concepts link to the idea of a Last Universal Common Ancestor before domain diversification

  • The taxonomy section underscores why Latinized, italicized names standardize communication across languages

  • The cellular vs acellular distinction frames the scope of microbiology (live cells vs. viral/prion particles)

  • Size and diffusion principles explain why cells stay small and how surface area-to-volume affects nutrient uptake and waste removal

  • The Miller–Urey experiments and RNA-world concepts provide a framework for how life’s monomers and polymers could arise abiotically and then become self-sustaining through replication

  • Cyanobacteria’s role connects biological evolution to atmospheric chemistry and the oxygenation of Earth

  • Endosymbiotic theory explains a major innovation in eukaryotic cells and the origin of mitochondria and chloroplasts