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38 Cards in this Set
- Front
- Back
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Viruses
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Plant, animal, and human diseases
*Can only reproduce by using metabolic machinery of a host cell even though they have a DNA and RNA genome, are host specific--rely on host's enzymes, ribosomes, transfer RNA, and ATP for its own reproduction |
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Virus Shape
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All viruses have an outer capsid composed of subunits and an inner core of nucleic acid, either DNA or RNA--capsid may be surrounded by an outer membranous envelope, may also contain enzymes used to produce viral DNA or RNA
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Virus categorization
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1)Their type of nucleic acid, incuding whether it is single stranded or double stranded
2)Their size and shape 3)The presence or absence of an ouiter envelope |
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Comparison of Viruses and Prokaryotes
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Viruses: don't have a cell wall, don't metabolize, don't respond to stimuli, they do multiply (always inside a living cell), and they do evolve
2)Prokaryotes: do have a cell wall, do metabolize, do respond to stimuli, do multply (usually independently), do evolve |
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Different types of viruses
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Bacteriophages (simply called phages), only work on bacteria
Two types of life cycles: lytic cycle, lysogenic cycle |
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Lytic Cycle
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Viral reproduction occurs, host cell undergoes lysis (breaking open of the cell to release viral particles
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Five Stages of Lytic Cycle
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1)Attachment-portions of the capsid combine with a receptor on the rigid bacterial cell wall in a lock and key manner
2)Penetration-viral enzyme digest away part of the cell wall, viral DNA is injected into the bacterial cell 3)Biosynthesis-begins after the virus brings about inactivation of host genes not necessary to viral replication, virus takes over the machinery of the cell in order to carry out viral DNA replication and production of multiple copies of the capsid protei subunits 4)Maturation-viral DNA and capsids assemble to produce several hundred viral particles, lysozyme (an enzyme coded for by a viral gene) is produced, disrupts the cell wall 5)Release-new viruses are released, bacterial cell dies as a result |
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Lysogenic Cycle
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From the Greek words lyo- loose, break up and genitus-producing___the infected bacterium does not immedialtely produce phage but will sometime in the future, in the meantime the phage is latent, not actively replicating, next integration occurs meaning that viral DNA becomes incorporated into bacterial DNA with no destruction of host DNA
While latent viral DNA is called prophage, it is replicated along with the host DNA and all subsequent cells (lysogenic cells) carry a copy of the prophage Certain environmental factors eg. ultraviolet rays can induce the biosynthesis, maturation, and release of the lytic stage |
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Animal viruses
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Examples: rabies (only infects mammals)
Reproduction: Similar to bacteriophages The viral genome covered by the capsid and envelope from host plasma membrane attach and fuse with the host cell After getting inside the virus is uncoated meanig that the capsid and evelope are removes, leaving the viral genome-either DNA or RNA ist free of covering and biosynthesis, maturation, and release can now take place Viral release occurs by budding-the virus picks up its envelope of lipids proteins and carbohydrates from the plasma membrane Envelope markers like the glycoproteins that allow the virus to enter a host are coded for by viral genes |
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Retroviruses
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RNA animal viruses that have a DNA stage, and example of a retrovirus is HIV
Contain special enzymes called reverse transcriptase which carries out RNA to cDNA transcription (DNA is called cDNA because i is the copy of the viral genome A double-stranded DNA is meshed with the host genome, where is remains and is replicated when the host's DNA is replicated, after this happens new viruses are produced by biosyntheses, maturation, and release, the cell is not destroyed the new viruses are created by budding |
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Emerging viruses
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Newly formed viruses in humans__AIDS, West Nile Virus, HPS-hantavirus pulmonary syndrome, SARS-severe acute respritory syndrome, Ebola hemorrhagic fever, and bird flu
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Viriods
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Naked strands of RNA not covered by a capsule which cause diseases in plants
Direct the cell to produce more viroids |
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Prions
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Proteinaceous infectious particles--basically rogue protein
Prion protein is found in healthy brains has an unknown function Disease happens when a normal prion protein changes shape and the polypeptide chain has a different configuration resulting in a fatal neurodeginerative disorder Rogue prions can interact with normal prion proteins and change the normal proteins shape An example of a prion caused disease is mad cow disease |
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Prokarotes
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Include bacteria and archaea-fully functioning cells
Bacteria are abundant in air, water, and soil and on most objects Combined number of procaryotes are higher than any other living organism on Earth |
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Prokaryotes detailed
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Prokaryotes means before a nucleus, lack a eukaryotic cell, and thus the membranous organelles of eukaryotic cells-various metabolic pathwaus are located on the inside of the plasma membrane
There were prokaryotic as long ago as 3.5 billion years ago and they were alone for 1.3 billion years ago Extremely diverse in structure and metabolic capabilities Can live in most environments because of the difference in the way they aquire energy |
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Prokaryotes Structure
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Bacteria-have an outer cell wall theat is strengthened by peptidoglycan-a complex molecle containing a unique amino disaccharide and peptide fragments, prevents them fom bursting or collapsing de to osmotic changes, may be surrounded by a layer of polysaccharides called glycocalyx-when well -organized, is called a capsule, loosely organized is called a slime layer, in parasitic forms theses coverings protect the cell fom host defenses
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Flagella
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Help move some prokaryotes
Had a filament made of three strands of the protein flagellin wound in a helix Filimant is inserted into a hook that is anchored by a basal body Flagellum rotates 360 degrees causes the the cell to spin and move forward |
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Fimbriae
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Short bristlelike fibers extending from the surface, used by prokaryotes to adhere to surfaces
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Nucleoid
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In proakaryotes instead of a nucleus, consist of single layer of consisting largley of a curcular straind of DNA, very dense in structure
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Plasmids
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Accessory rings of DNA found in many prokaryotes, can be extracted and used as vectors to carry foregn DNA into host bacteria during genetic engineering processes
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Protein synthesis in prokaryotic cells
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Carried out by thousands of ribosomes
Diagram Prokaryotic Cell Cell Envelope Glycocalyx Cell Wall Plasma Membrane Cytoplasm Nucleiod Ribosomes Thykaloids (cynobacteria) Appendages Flagella Sex pilus Fimbriae |
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Reproduction in prokaryotic cells
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Reproduce asexually through binary fission
-A single circular chromosome replicates, and then two copies separate as the cell enlarges, newly formed plasma membrane and cell wall separate the cell wall into two cells --Mitosis which requires the formation of a spindle apparatus, does not occur in prokaryotes |
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Prokaryotes regeneration
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12 minutes, this mutations are generated and passed on to offspring more quickly than in eukaryotes, prokaryotes are also haploid so mutation are immediately affected by natural selection, which determines any possible adaptive features
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Genetic recombination in prokaryotes
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In eukaryotes results from sexual reproduction
In bacteria three ways of genetic recombination have been observed 1)Conjugation- occurs between bacteria when the donor cell passes DNA to the recipient cell by way of the sex pilus, which temporarily joins the two cells, takes place only between bacteria in the same of closely related species 2)Transformation-occurs when bacterium picks up (from the surroindings) free pieces of DNA sextred by living or dead prokaryotes 3)Transduction-bacteriophages carry portions of bacterial DNA from one cell to another -plasmids, which sometimes carry genes for resistance to antobiotics, can be trensferred between infectious bacteria by any of these three ways |
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Endospores
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Created by bacteria during less than favorable conditions, a portion of the cytoplasm and a copu of the chromosone dehydrate and are then encased by a heavy protective spore coat, sometimes the rest of the bacteria deteriorates and the endospore is released, can survive in the harshist of environment--desert heat and dehydration, bouling temperatures, polar ice, extreme ultraviolet radiation, can also survive for long periods of time, not a means of reproduction, just of surviving and moving to other areas of the world
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Prokaryotic Nutrition
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Some are obligate anaerobes-unable to grow in the presence of free oxygen, some are facultative anaerobes-able to grow in either the presence of the absence of gasous oxygen, most are aerobic and require oxygen to carry ou cellular respiration
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Autotrophic Prokaryotes
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Bacteria called photoautotrophs are photosynthetic, use solar energy to reduce carbon dioxide to organic compounds, there are two kinds
1)bacteria that evolved first and do not give off oxygen *photosystem 1 only *unique type of chlorophyll called baceriochlorophyll 2)bacteria that evolved later and do five off oxygen *photosystmes 1 and 2 *type of chlorophyll a found in plants examples of these--green sulfer bacteria and some purple carry on the first type of photosynthesis, do not give off oxygen because they do not use water as an electron donor, can use things like hydrogen sulfide--these bacteria usually live in anaerobic conditions such as the muddy bottom of a march and they cannot photosynthesize in the presence of oxygen |
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Bacteria
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Doamin Bacteria, more common type prokaryote
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Bacteria
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Prokaryotic cells with prokaryotic cell structure
non-nucleated cells, cell wall made of peptidoglycan, usually differentiate bacteria by using the Gram stain procedure |
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Gram-positive
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Retain a dye-iodine complex and apper purple under a light microscope
Have a thick layer of peptidoglycan in thier cell walls Include: Kingdom Deinococi--Deinococcus Kingdom Firmicutes--Streptococcus, Listeria, Staphylococcus Kingsom Actinobacteria--Mycobacteria, Nocardia |
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Gram-negative
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Does not retain dye-iodine complex and appear pink
Have a thik layer of peptidoglycan Include: Kingdom Cyanobacteria--Prochloron, Oscillatoria, Anabaena Kingdom Proteobacteria--Rhodospirillum, Rhizobium, etc. Kingdom Spirochetes--Borrelia, Leptospira Kingdom BActeriadetes--Bacteriodes, Porphyromonas |
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Bacteria and Archaea
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Can be classified by 3 basic shapes
1)Spirillum---spiral-shaped or helical-shaped 2)Bacilli---rod-shaped 3)Cocci---Round or spherical (may be augmented by particular arrangement or shapes of cells) Other forms of classification include, presence of endospores, metabolism, growth, nutritional characteristics, and other physiological features |
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Domain Bacteria
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Prokaryotic, Unicellular organisms that lack a membrane-bounded nucleus, Reproduce asexually, Metabolically diverse, many being heterotrophic by absorption, others being autotrophic by chemosynthesis or by photosynthesis, Motile forms move by flagella consisting of a single filament
Others included and not mentioned before: Kingdom Aquificae--Aquifex Kingdom Chloroflixi--Chlorobium, Herpetosiphon Kingdom Planctomycetes--Planktomyces |
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Domain Archaea
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Prokaryotic
Unicellular organisms tat lack a membrane-bounded nucleus Reproduce asexually Metabollically diverse, many being autotrophic by chemosyntheses and afew by photosynthesis, some being heterotrophic by absorption Distinguish from bacteria by their unique rRNA base sequence and their distinctive plasma membrane and cell wall chemistry Include: Kingdom Euryarchaeota--Halobacterium, Methanobacterium, Picrophilus, Thermococcus Kingdom Crenarchaeota--Pyrodictium, Pyrolobus, Pyrobaculum Kingdom Korarchaeota |
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Cyanobacteria
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-Gram-negative
-Photosynthesize in the same manner as plants, first to introduce oxygen to atmosphere -Known as blue bacteria, but can contain pigments that mask their true color so they appear red, yellow, brown, or black -Cells are large -Can be unicellular, colonial, or filamentous -Lack any visible means of locomotion (some glide when in contact with solid surface, and other sway back and forth-oscillate) -Some have heterocyst-thick walled cells without a nuclei, where nitrogen fixation occurs, thus nutritional requirements are minimal -Can serve as food for heterotrophs -Common in fresh and marine waters, soil, on moist surfaces, also found in harsh habitats such as hot springs -Symbiotic with many organisms-liverworts, ferns, corals -Form lichens with fungi--can grow on rocks, provides organic nutrients for fungus, while fungus protects and furniches inorganic nutrients to cyanobacterium *Lichens help form rock into soil--thought that cyanobacteria were the first colonizers of land on earth |
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Archaea
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Prokaryotes with biochemical characteristics that make them different from both bacteria and eukaryotes
-rRNA has a different base sequence from the rRNA of bacteria -Thought to be more closely related to eukaryotes than to bacteria--share some of the same ribosomal proteins not found in bacteria, iitiate transcription the same way, have similar types of tRNA |
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Structure of Archaea
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-Plasma membranes contain lipids that allow them to function at high temps.
-Evolved diverse cell wall types, also help them to survive in extreme conditions -Cell walls do not contain peptidoglycan, largly composed of polysaccharides in some, and pure protein in others. some have no cell wal Metabolically-- Methanogenesis, the ability to form methane, in some archaea called methanogens -Most archaea are chemoautotrophs--oxidize inorganic compounds to obtain the necessary energy to reduce oxygen to an organic compound, a few are photosynthetic -Sometimes mutualistic or commensalistic, but none are parasitic |
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Types of Archaea
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-Methanogens, make methane, found in anaerobic environments--swamps, marshes, intestinal tracts of animals, used hydrogen gas to reduce carbon diozide to methane and couple the energy to release ATP production
-Halophile-require high salt concentration for growth, found in The Great Salt Lake, the Dead Sea, solar salt ponds, and hypersaline soils, their proteins have unique chloride pumps that use halorhodopsin to pump chloride into their cells, preventing water loss, also use pigment bacteriohodopsin to synthesize ATP in light -Thermoacidophiles-found in extremely hot environments, hot springs, geysers, submarine thermal vents, around volcanoes, reduce sulfides, survive best around temps above 80 degrees celcius,and as high as 105 degrees celcius, metabolism of sulfides results in acidic sulfates |
