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prokaryotes
unicellular organisms that lack a nucleus
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*How do the two groups of prokaryotes differ?
*Archaebacteria lack the peptidoglycan of eubacteria and also have different membrane lipids. Also, the DNA sequences of key archaebacterial genes are more like those of eukaryotes than those of eubacteria.
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*What factors can be used to identify prokaryotes?
*Prokaryotes are identified by characteristics such as shape, the chemical nature of their cell walls, the way they move, and the way they obtain energy.
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bacilli
- rock-shaped prokaryotes
- (singular: bacillus)
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cocci
- spherical prokaryotes
- (singular: coccus)
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spirilla
- spiral and corkscrew-shaped prokaryotes
- (singular: spirillum)
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chemoheterotrophs
organism that must take in organic molecules for both energy and carbon
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photoheterotrophs
organism that is photsynthetic but needs organic compounds as a carbon source
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photoautotrophs
organisms that use energy from sunlight to convert carbon dioxide and water to carbon compounds
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chemoautotrophs
organism that makes organic carbon molecules from carbon dioxide using energy from chemical reactions
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obligate aerobes
organisms that require a constant supply of oxygen in order to live
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obligate anaerobes
they must live in the absence of oxygen
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facultative anaerobes
third group of bacteria that can survive with or without oxygen
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binary fission
type of asexual reproduction in which an organsims replicates its DNA and divides in half, producing two identical daughter cells
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conjugation
form of sexual reproduction in which paramecia and some prokaryotes exchange genetic information through a connecting hollow bridge
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endospore
type of spore formed when a bacterium produces a thick internal wall that encloses its DNA and a portion of its cytoplasm
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*What is the importance of bacteria?
*Bacteria are vital to maintaining the living world. Some are producers that capture energy by photosynthesis. Others are decomposers that break down the nutrients in dead matterand the atmosphere. Still other bacteria have human uses.
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nitrogen fixation
process of converting nitrogen gas into a form plants can use
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viruses
particles of nucleic acid, protein, and in some cases, lipids
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*What are the parts of a virus?
*A typical virus is composed of a core of DNA or RNA surrounded by a protein coat.
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capsid
the virus's protein coat that includes proteins that allow a virus to enter a host cell
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bacteriophages
viruses that infect bacteria
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*How do viruses cause infection?
*In a lyctic infection, a virus enters a cell, makes copies of itself, and causes the cell to burts.
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lyctic infection
process in which a virus enters a cell, makes a copy of itself, and causes the cell to burts
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lysogenic infections
host cell makes copies of the virus indefinitely
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*How do viruses cause infection?
*In a lysogenic infection, a virus integrates its DNA into the DNA of the host cell and the viral genetic information replicates along with the host cell's DNA.
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prophage
the viral DNA that is embedded in the host's DNA
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retroviruses
viruses that contain RNA as their genetic information
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pathogens
disease-causing agents
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*How do bacteria cause disease?
*Bacteria produce desease in one of two ways. Some bacteria damage the cells and tissues of the infected organism directly by breaking down the cells for food. Other bacteria release toxins (poisons) that travel throughout the body, interferring with the normal activity of the host.
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vaccine
preparation of weakened or killed pathogens that prompts te body to produce immunity to the disease
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antibiotics
compounds that block the growth and reproduction of bacteria
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*How can bacterial growth be controlled?
*There are various methods used to control bacterial growth, including sterilization, disinfectants, and food processing.
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