BackCell Structure and Function: Microbial Cell Types and Characteristics
Study Guide - Smart Notes
Tailored notes based on your materials, expanded with key definitions, examples, and context.
Chapter 3: Cell Structure and Function
Processes of Life
All living organisms share certain fundamental processes that define life. These processes are essential for the survival, growth, and reproduction of cells, including microbes.
Growth: An increase in size of an organism or cell.
Reproduction: The process by which organisms produce new individuals or cells.
Responsiveness: The ability to sense and respond to environmental stimuli.
Metabolism: Controlled chemical reactions that occur within an organism to maintain life.
Characteristics of Life and Their Distribution in Microbes
Microbes, including bacteria, archaea, eukaryotes, and viruses, exhibit varying degrees of these life characteristics. The table below summarizes the distribution of these traits among different microbial groups.
Characteristic | Bacteria, Archaea, Eukaryotes | Viruses |
|---|---|---|
Growth (increase in size) | Occurs in all | Growth does not occur |
Reproduction (increase in number) | Occurs in all | Host cell replicates the virus |
Responsiveness (react to environmental stimuli) | Occurs in all | Reaction to host cell seen in some viruses |
Metabolism (controlled chemical reactions) | Occurs in all | Viruses use host cell's metabolism |
Cellular structure (membrane-bound structure capable of all above functions) | Present in all | Viruses lack cytoplasmic membrane or cellular structure |
Example: Bacteria can grow and divide independently, while viruses must infect a host cell to reproduce and do not grow in size.
Types of Cells: Prokaryotic vs. Eukaryotic
Prokaryotic Cells: An Overview
Prokaryotic cells are structurally simpler than eukaryotic cells and are found in the domains Bacteria and Archaea.
Lack a nucleus: Their genetic material is not enclosed within a membrane-bound nucleus.
Simultaneous DNA reading and protein synthesis: Transcription and translation can occur at the same time.
Lack internal membrane-bound organelles: No mitochondria, endoplasmic reticulum, or Golgi apparatus.
Small size: Typically 1.0 μm in diameter or smaller.
Examples: Escherichia coli (bacterium), Halobacterium (archaeon).
Eukaryotic Cells: An Overview
Eukaryotic cells are more complex and are found in organisms such as algae, protozoa, fungi, animals, and plants.
Have a nucleus: Genetic material is enclosed within a nuclear envelope.
Contain internal membrane-bound organelles: Includes mitochondria, endoplasmic reticulum, Golgi apparatus, etc.
Larger size: Typically 10–100 μm in diameter.
More complex structure: Specialized compartments allow for division of labor within the cell.
Examples: Saccharomyces cerevisiae (yeast), Paramecium (protozoan), plant and animal cells.
Additional info: The distinction between prokaryotic and eukaryotic cells is fundamental in microbiology, as it underpins differences in genetics, metabolism, and susceptibility to antibiotics.
