2.1- Prokaryotic Cell Structure Part 1

Introduction

• Presenter: Dr. Narelle Hunter

• Focus of Lecture: Structure of Prokaryotic Cells

• Recommended Reading: Chapter 6 of the textbook, with Chapters 2-5 as assumed knowledge.

Learning Outcomes

• Understand the microscopic structure of cells.

• Cells as fundamental units of life.

• Common features among diverse cell types.

Importance of Cells

• Cells are the foundation of all life.

• Study of biology revolves around cell structures and functions.

Common Features of All Cells

• Plasma Membrane: All cells are bounded by this structure.

• Cytosol: Contains a semi-fluid substance within the cell.

• Chromosomes: Carries genetic information in the form of DNA.

• Ribosomes: Complexes that make proteins based on genetic instructions.

Classification of Cells

Types of Cells

• Prokaryotic Cells: Include bacteria and archaea.

• Eukaryotic Cells: All other living organisms, including animals, plants, and fungi.

Cell Naming and Features

• Prokaryotic: "Pro" means before; "karyon" means nucleus (no true nucleus).

• Eukaryotic: "Eu" means true; cells have a true nucleus.

Size Comparison

• Prokaryotic Cells: Generally 1 to 10 micrometers, not visible to the naked eye.

• Eukaryotic Cells: Typically 10 to 100 micrometers; examples include nerve cells which can be up to 1 meter long.

Prokaryotes

• Historical Context: Dominant life forms on Earth for 3.5 to 2 billion years.

• Structure: Lack a nucleus; DNA is in the nucleoid region.

• Reproduction: Fast reproduction through binary fission (asexual reproduction).

• Examples:

  • Vibrio natrigens: Fastest growth rate <10 min doubling time.

  • E. Coli: Commonly found in intestines, with a doubling time of ~20 minutes.

Shapes of Prokaryotes

• Cocci: Spherical shape.

• Bacilli: Rod-shaped.

• Spiruli: Helical shape.

Metabolic Adaptations of Bacteria

• Obligate aerobes: Require oxygen for metabolism.

• Anaerobes: Do not require oxygen (includes obligate and facultative anaerobes).

Positive Roles of Bacteria

• Importance in human health, particularly gut health and diseases like IBS.

• Probiotics: Beneficial bacteria aiding in digestion.

Research Advances

• Study example from Japan relates gut microbiome to dementia.

• Complexity of bacterial relationships in health yet to be fully understood.

Discovery Challenges

• Approximately 30,000 bacterial species formally identified; many undiscovered.

• Typical methods are inadequate for discovering new bacterial species due to growth requirements.

• Innovation in Research:

  • Professor Slava Epstein researching new antibiotics derived from undiscovered bacteria.

  • Example experiment used mouth retainers for bacteria cultivation.

Importance of Bacterial Cell Wall

• Provides shape, protection, and prevents bursting in hypotonic environments.

• Gram Staining: Laboratory technique to analyze cell wall composition through color differences.

Conclusion

• Understanding bacteria is crucial due to their vast diversity and role in ecosystems.

• Further research is necessary to uncover more about prokaryotic cells and their applications in medicine.