Overview
This lecture covers the basic structure and functions of prokaryotic cells, focusing on their unique features, components, and roles in various environments.
Types and Environments of Prokaryotes
- Prokaryotic cells include two main groups: bacteria and archaea.
- They are the oldest living organisms, existing for about 3.5 billion years.
- Prokaryotes inhabit diverse environments such as soil, water, and the human body.
Structural Components of Prokaryotic Cells
- Many prokaryotes have a sticky carbohydrate outer layer called the capsule for surface attachment.
- A cell wall surrounds the cell, providing structural support and protection; it usually contains peptidoglycan.
- The plasma membrane consists of lipids and proteins and is selectively permeable, regulating molecular entry and exit.
- The cytoplasm is a gel-like substance hosting cellular components and metabolic processes.
Appendages and Motility
- Some prokaryotes possess flagella, long structures enabling movement in liquid environments.
- Pili (fimbriae) are short, hair-like appendages that aid in attachment to surfaces or other cells, helping in colonization and biofilm formation.
Genetic Material and Protein Synthesis
- The nucleoid is a region containing the cell’s circular DNA, without a surrounding nuclear membrane.
- Plasmids, small circular DNA pieces, may be present and can be transferred between cells.
- Ribosomes in the cytoplasm synthesize proteins essential for cell function.
Capabilities of Prokaryotic Cells
- Despite their simplicity, prokaryotic cells perform all life functions, including growth, reproduction, and response to environmental stimuli.
Key Terms & Definitions
- Prokaryote — organism without a nucleus or membrane-bound organelles.
- Capsule — sticky carbohydrate layer aiding surface attachment.
- Cell wall — rigid outer layer providing structure and protection, often made of peptidoglycan.
- Plasma membrane — selectively permeable barrier of lipids and proteins.
- Cytoplasm — gel-like substance containing cell structures and facilitating reactions.
- Flagellum — whip-like tail aiding in cell movement.
- Pili (fimbriae) — short, hair-like structures for attachment.
- Nucleoid — region containing prokaryotic DNA.
- Plasmid — small, transferable circular DNA molecule.
- Ribosome — molecular machine for protein synthesis.
Action Items / Next Steps
- Review the structures and functions of prokaryotic cell components.
- Prepare a diagram labeling features of a typical prokaryotic cell.