Term
| What are the The Simplest Organisms? |
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Definition
| The fossil record indicates that prokaryotes appeared 2.5 billion years ago
Eukaryotes, on the other hand, appeared only 1.5 billion years ago
Today prokaryotes are the simplest and most abundant form of life on earth
Prokaryotes occupy a very important place in the web of life in earth |
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Term
| What is the The Structure of a Prokaryote? |
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Definition
| Prokaryotes are small, simply organized, single cells that lack a nucleus
Prokaryotes include the bacteria and archaebacteria
They come in three main shapes
Rod-shaped (bacilli)
Spherical (cocci)
Spirally coiled (spirilli) |
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Term
| What is the cell membrane encased in? |
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Definition
| The cell membrane of prokaryotes is encased in a cell wall
Bacterial cell walls are composed of peptidoglycan
Network of polysaccharides linked together by peptide cross-links |
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Term
| What do Archaebacterial cell walls lack ? |
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Definition
peptidoglycan
They are made of proteins, sugars or both. |
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Term
| What two groups can Bacteria can be divided into? |
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Definition
| Gram-positive
Have a thick peptidoglycan layer
Lack outer membrane
Gram-negative
Have a thin peptidoglycan layer
Have an outer membrane containing lipopolysaccharide
The name refers to a differential stain developed by Hans Christian Gram
Gram-positive cells retain the primary crystal violet stain
Gram-negative cells don’t and are stained by a safranin (red) counterstain |
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Term
| The structure of bacteria cell walls (diagram). |
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Definition
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Term
| What are a list of things that bactera may have? |
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Definition
| Many bacteria have capsules
A gelatinous layer found external to the cell wall
Many bacteria possess threadlike flagella
Long external appendages used for locomotion
Some bacteria also possess pili
Short external appendages used for attachment
In harsh conditions, a few bacteria can form endospores
Highly-resistant structures that may germinate into active bacteria when conditions improve |
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Term
| How does bacteria reporoduce? |
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Definition
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Term
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Definition
| Plasmids are (typically) circular double-stranded DNA molecules that are separate from the chromosomal DNA
Plasmids often contain genes that confer a selective advantage to the bacterium harboring them, e.g., the ability to make the bacterium antibiotic resistant. |
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Term
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Definition
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Term
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Definition
| Bacteria such as Neisseria gonorrhoeae use pili to adhere to the mucous membranes of the urethra and thus resist the flushing action of the urine. |
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Term
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Definition
| F (conjugation, sex) pili
F pili are long pili found in low numbers and used to attach one bacteria to a another, typically of the same species.
F pili are involve in the transfer of plasmids from one bacteria to the other, a process called conjugation. |
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Term
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Definition
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Term
| What is a bacteria conjugation? |
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Definition
| The undirectional transfer of plasmid DNA following cell-to-cell contact. |
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Term
| Comparing Prokaryotes to Eukaryotes |
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Definition
| Prokaryotes differ from eukaryotes in many respects
They have very little internal organization
They are unicellular and much smaller
They possess a single chromosome
They are far more metabolically diverse (different means of obtaining energy) |
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Term
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Definition
| Prokaryotes have evolved many more ways than eukaryotes to acquire carbon and energy
Acquisition of Carbon
Autotrophs = Use CO2 as their only carbon source
Heterotrophs = Use preformed organic compounds as carbon sources
Acquisition of Energy
Phototrophs = Use light as energy source
Chemotrophs = Use chemicals as energy source |
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Term
| Prokaryotic Metabolism (2) |
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Definition
| Based on carbon and energy sources, prokaryotes can be divided into four categories
1. Photoautotrophs
Use the energy of sunlight to build organic molecules from CO2
Cyanobacteria
2. Chemoautotrophs
Obtain energy by oxidizing inorganic substances
Nitrifiers oxidize ammonia or nitrite |
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Term
| Prokaryotic Metabolism (2) |
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Definition
| Based on carbon and energy sources, prokaryotes can be divided into four categories
3. Photoheterotrophs
Use light as energy and pre-formed organic molecules as carbon sources
Purple nonsulfur bacteria
4. Chemoheterotrophs
Use organic molecules as carbon and energy sources Decomposers and most pathogens |
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Term
| Importance of Prokaryotes |
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Definition
| Prokaryotes were largely responsible for creating the properties of the atmosphere and soil found on Earth
They are the principal decomposers
They are the only organisms capable of fixing nitrogen, thus making it available for others
They cause major diseases in plants and animals, including humans |
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Term
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Definition
Prokaryotes are instrumental in genetic engineering
Nonpolluting insect control agents
Removing environmental pollutants |
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