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Prokaryotes: Single-celled Organisms
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What is a Prokaryote?
- There are two basic types of organisms based on cell type: Prokaryotic and Eukaryotic.
- Prokaryotic cells are divided into the domains Bacteria and Archaea.
- Eukaryotic cells make up the more familiar Domain Eukarya.
- Prokaryotic cells are divided into the domains Bacteria and Archaea.
- Prokaryotes are the smallest forms of life that can live independently.
- Most prokaryotes are tiny single cells, but some can form larger, multi-celled structures.
- The first life on earth consisted of prokaryotic cells.
- Most prokaryotes are tiny single cells, but some can form larger, multi-celled structures.
- The most familiar prokaryotes are bacteria.
- Bacteria are a very diverse group that have several shapes, depending on the species.
- The archaea are also quite diverse, but resemble the bacteria in general appearance.
- Bacteria are a very diverse group that have several shapes, depending on the species.
- Some prokaryotes, mainly in domain Archaea, can live in extreme environments.
- Extreme thermophiles live in hot places such as volcanic springs and hydrothermal vents.
- Extreme halophiles live in water of high saline content, and acidophiles thrive at very low pH.
- Methanogens are poisoned by oxygen and live in places like swamps and the gut of animals.
- Many biologists believe that if life exists elsewhere in our solar system, it will resemble thermophiles and methanogens; fossils of prokaryotes in meteorites have recently been reported.
- Prokaryotes have been utilized as sources of enzymes that work under extreme conditions.
Prokaryotic Cells: What Structures Are Present in All Cells?
- There all several essential structures that all cells must have to survive.
- The plasma membrane separates the cell from its environment and serves as a "gate keeper".
- The membrane has a lipid-protein structure.
- Phospholipids provide fluidity within the membrane and form a selectively permeable barrier.
- Hydrophobic substances and some small molecules can move through the lipid layers by diffusion.
- Membrane proteins play a crucial role in moving hydrophilic substances across the membrane; some proteins can move molecules against a concentration gradient, as you will learn later in the course.
- Membrane proteins can also function as enzymes or as signal transducers.
- The membrane has a lipid-protein structure.
- The genome within a chromosome serves as the control center for the cell.
- The chromosome of most prokaryotes is circular and packed within the nucleoid region.
- Bacterial cells may also have separate pieces of DNA called plasmids.
- The chromosome of most prokaryotes is circular and packed within the nucleoid region.
- Ribosomes are the "work bench" on which proteins are made; the resulting proteome gives cells their specific structure and function.
Prokaryotic Cells: What Are Some Additional Features of These Cells?
- Most prokaryotic cells have additional structures.
- Almost all prokaryotes have a cell wall; bacteria can be divided into two groups based on the structure of their cell wall and how it responds to Gram staining technique.
- Some prokaryotes have a capsule external to the cell wall that may bear hair-like appendages.
- About 50% of all prokaryotes are motile; most of them utilize flagella for directional movement.
- Almost all prokaryotes have a cell wall; bacteria can be divided into two groups based on the structure of their cell wall and how it responds to Gram staining technique.
- When you view the electron micrograph of a real cell, it never looks exactly like its cartoon or diagram.
