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The Single Cell: Viruses, Bacteria, & Protists What do you notice as the levels go from atom to organism? Once at the organism level how do we organize? Why are levels of organization important? Structure: Viruses, Bacteria, & Protists What is a Virus? ½ to 1/100 the size of the smallest bacteria DNA or RNA Classification on basis of nucleic acid DNA viruses: - Herpes simplex virus (HSV) RNA viruses: - influenza virus Structure of a Virus? Envelope – additional layer surrounding the capsid Genetic material Capsid - a shell of protein surrounding nucleic acid Capsid Envelope Lipid bilayer Proteins determine the viruses shape: Polyhedral - papilloma virus with projections - HIV helical - tobacco mosaic virus Polyhedral head w/cylindrical tail w/ leg fibers What are Bacteria? Kingdom Archebacteria Prokaryote Extreme environment No free O2 High salt or sulfur concentration Some produce methane What are Bacteria? Kingdom Eubacteria Human pathogens Decomposers Symbiotic living Prepare food Make antibiotics Structure of Bacteria Prokaryotic cells lack a nucleus and membrane bound organelles Common shapes among prokaryotes are spheres, rods, & spirals What are Protists? Kingdom Protista All organisms that are neither animals, plants, bacteria or fungi are called 'protists' Unicellular, multicellular, colonial Eukaryotic Aquatic environments What are Protists? Plant like Protists - Algae Live in fresh or salt water Reproduction & metabolism similar to plants Animal like Protists - Protozoa Ciliate Flagellate Aquatic All are single celled Pseudopod Metabolism similar to animals Grouped according to how they move Fungus like Protists – plasmodium, slime mold, downy mildew Behavior & metabolism similar to fungus Sporazoan Reproduction: Viruses, Bacteria, & Protists Viral Reproduction Lytic Cycle The viruses attaches to a host cell and deposits its DNA The viral DNA instructs the host cell to use its own enzyme raw material & energy to only make new viruses The new viruses burst from the host cell – killing it – & are able to go infect other cells •Attachment •Entry •Replication •Assembly •Release Viral Reproduction Lysogenic Cycle The viral DNA is integrated into the host cells chromosome - provirus Every time the host cell replicates it also replicates the viral DNA Once activated, the provirus enters the lytic cycle replicates and kills the host cell •Attachment •Entry •Provirus formation •Replication •Assembly •Release Bacterial Reproduction Most prokaryotes have a single, circular, double-stranded DNA chromosome condensed in the nucleoid region of the cytoplasm Many bacteria have an additional small ring of DNA – The Plasmid – prokaryotes can survive without the plasmid the genes for essential functions are on the chromosome. Plasmids sometimes contain genes for resistance and other special issues Bacterial Reproduction ASEXUAL No cell cycle like seen in Eukaryotes No mitosis or meiosis Prokaryotes reproduce mostly asexually via binary fission, making DNA almost continuously Translation and transcription occur simultaneously Allows for rapid response to Environment – ADAPTATION Bacterial Reproduction SEXUAL Conjugation, one cell directly transfers DNA to another Resulting in a bacterium with a new genetic composition Plant Like Protist Reproduction Asexual & Sexual Fragmentation occurs when a filament breaks apart and each piece develops into another organism. Spirogyra Conjugation occurs when two filaments form conjugation tubes. The contents of one cell passes through the tube an fuses with a cell from the other filament. Fertilization occurs and a zygote is formed. (haploid) Alternation of generations Sexual (haploid) (haploid) and asexual reproduction occurs during alternating periods in the life cycle of the plant like protist. (diploid) (diploid) (diploid) Animal Like Protist Reproduction Multiply asexually by fission. The cell divides into two individuals. Paramecium undergoing fission. Fungus Like Protist Reproduction Plasmodium - Reproduces by haploid spores Slim molds are haploid their entire life & reproduce by cell division Metabolism: Viruses, Bacteria, & Protists Do viruses need energy? Do viruses need to “eat”? Do viruses produce waste? Do viruses have a metabolism? Heterotrophic Bacteria Use organic molecules as a food source Parasites – Unable to produce organic molecules Obtain nutrients from living organisms Excretes waste thru cell wall Saprophytes – Feed on dead organisms or organic waste Break down nutrients locked in body tissues of dead organisms Excretes waste thru cell wall Autotrophic Bacteria Use sunlight to make organic molecules Photosynthetic autotrophs – Contain chlorophyll Excretes waste thru cell wall Make organic molecules from inorganic ones Chemosynthetic autotrophs – Obtain energy needed to make food from Chemicals like sulfur & nitrogen Excretes waste thru cell wall Protists Plant like Able to perform photosynthesis contain chlorophyll Not all are green. Diatoms & dinoflagellates have yellow to brown chloroplasts. There are brown algae & red algae Release waste thru cell wall Animal like Heterotrophic – feed on other organisms or dead organic matter. Some are parasitic Have specialized organelles used to release waste Fungus like Heterotrophic Plasmodium Eats as it moves Mildew Feed on dead organisms Releases waste thru cell membrane Gas Exchange: Viruses, Bacteria, & Protists Why is gas exchange important? Do viruses need oxygen or carbon dioxide? Bacteria Metabolism Obligate aerobes – require oxygen Mycobacterium tuberculosis – the organism that causes the lung disease tuberculosis Obligate anaerobes – require NO oxygen Treponema pallidum – the bacterium that causes syphilis Bacteria Metabolism Prokaryotes used infolded regions of the plasma membrane to perform many metabolic functions, including cellular respiration and photosynthesis. Respiratory membranes in aerobes Heterotroph Thykaloid membranes in photosynthetic bacteria Autotroph Protists Metabolism Protists are eukaryotic cells Have many specialized organelles including mitochondria or chloroplasts used in cellular respiration Protists are aerobic – they require oxygen Paramecium Homeostasis: Viruses, Bacteria, & Protists What is HOMEOSTASIS? Why is it important? How do VIRUSES maintain homeostasis? The Host Cell does it for them!! Bacteria Homeostasis The cell wall maintains the shape of the cell, protects the cell, and prevents the cell from bursting in a hypotonic environment When life gets rough some bacteria can form resistant endospores Endospores contain a bacterium’s DNA and a small amount of cytoplasm Endospores are encased in a tough outer covering that resists drying out and extreme temperatures Protist Homeostasis Because the kingdom protista contains such a variety, several homeostatic behaviors exist If you would keep Euglenoids in the dark they start feeding on organic matter and may loose their chloroplast. Sometimes classified as animal like other times classified as plantlike Amoebas can grow to very large sizes. Some species are 5 mm long! They can survive by having many nuclei within their single cell. Star-shaped contractile vacuoles are used to balance the amount of water in the cell. Two nuclei contain the genetic information. Are viruses alive What are the characteristics of life? How do characteristics of viruses compare to that of living organisms? Are viruses alive How do No cell characteristics of organization viruses compare to that of living organisms? Homeostasis?
