Overview
This lecture covers the basic structure and functions of prokaryotic cells, focusing on their main components and their roles in cellular life.
Prokaryotic Cell Basics
- Prokaryotic cells are the simplest and smallest living organisms.
- They have existed on Earth for around 3.5 billion years.
- Prokaryotes include two major groups: bacteria and archaea.
- Prokaryotes inhabit diverse environments such as soil, water, and the human body.
Structural Components of Prokaryotic Cells
- Many bacteria have a sticky capsule made of carbohydrates that helps cells attach to surfaces.
- All prokaryotes have a cell wall providing structural support and protection.
- The cell wall is typically composed of peptidoglycan, a polymer of sugars and amino acids.
- The plasma membrane, made of lipids and proteins, surrounds the cell and is selectively permeable.
Internal Features
- The cytoplasm is a gel-like substance inside the cell where cellular processes occur.
- The nucleoid is a circular piece of DNA containing genetic information, not enclosed by a membrane.
- Some prokaryotes also have plasmids, small circular DNA pieces that can be transferred between cells.
- Ribosomes in the cytoplasm are responsible for protein synthesis.
Surface Structures and Motility
- Some prokaryotes have flagella, long whip-like structures for movement in liquids.
- Pili (fimbriae) are short, hair-like structures that help cells attach to surfaces or other cells, aiding in colonization and biofilm formation.
Functions of Prokaryotic Cells
- Prokaryotic cells perform all life functions including growth, reproduction, and responding to environmental stimuli.
Key Terms & Definitions
- Prokaryote — a simple, small cell type lacking a nucleus, includes bacteria and archaea.
- Capsule — an outer carbohydrate layer aiding in attachment.
- Cell wall — rigid structure providing support; made of peptidoglycan in bacteria.
- Plasma membrane — selectively permeable barrier controlling molecule movement.
- Cytoplasm — gel-like internal substance where cell processes occur.
- Nucleoid — region containing the cell's circular DNA, not membrane-bound.
- Plasmid — small, circular DNA molecule that can be transferred between cells.
- Ribosome — cellular structure for protein synthesis.
- Flagellum — tail-like structure for movement.
- Pilus (fimbria) — hair-like projection aiding in attachment to surfaces.
Action Items / Next Steps
- Review the structure and function of each prokaryotic cell component for next class.