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Cell
- 1.Basic units of life
- 2. Robert Brown, Matthais Schleiden, Theodor Schwan
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Cell Theory
- All organisms are composed of cells.
- Cells are basic units of structure and function in organisms.
- Cells come only from preexisting cells because cells are self reproducing.
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Prokaryotic Cell
- Structurally less complicated.
- Lack membrane bound nucleus and organelles.
- Used to manufacture- industrial chems, foodstuff and drugs.
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Structure of Prokaryotes
Quiet small- 1.1-1.5 nm.
- Three basic shapes : bacillus-rod shaped(chains/pairs), coccus-spherical shaped(chains/pairs/clusters),if they are twisted or spirals-spirella(rigid) & spirochetes-flexible.
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Cell Envelope
- Includes: Plasma membrane, cell wall, glycocalyx.
- Plasma Membrane: Phospholipid bilayer with embedded proteins
- Cell wall : When present maintains shape of the cell, even if the cytoplasm should take up abundant water
- Glycocalyx :Layer of polysaccharides that lies outside cell wall in some bacteria. When not easily washed off- capsule. Aids against drying out- resist host immune system - attach to ay surface.
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Plasma membrane (pro)
- Regulates entrance and exit of substances into and out of cell- in order to maintain normal composition.
- Can form internal pouches-Mesosomes-increase internal surface area for attachment of enzymes that are carrying on metabolic activities.
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Cytoplasm (pro)
- Semi fluid solution- composed of water and inorganic and organic molecules encased in plasma membrane
- DNA found in single, coiled chromosome- located in nucleoid.
- Extra chromosomal pieces of cellular DNA- plasmids-Self-duplicating ring of accessory DNA in the cytoplasm of bacteria.
- Ribosomes :Self-duplicating ring of accessory DNA in the cytoplasm of bacteria. Bacterial ribosomes still contain RNA and protein in two subunits.
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Cyanobacteria
- Bacteria capable of photosynthesis.
- Organisms- live in water, ditches, buildings, bark of trees.
- Cytoplasm contains extensive internal membranes-thalakoids- chlorophyll and other pigments absorb solar energy for carbohydrate production.
- Called Blue-green algae.
- Release oxygen as byproduct of photosynthesis.
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Appendeges
Flagella, fimbriae, conjugation pilli- made of protein.
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Flagella
- Propel themselves in water.
- Consists- filament, hook, basal body.
- Basal Body- series of rings anchored in cell wall and membrane.
- Hook- rotates 360 within the basal body, this propels bacteria.
- Sometimes occur only at the two ends of a cell, and sometimes dispersed randomly over a surface
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Fimbriae
- Small, bristle-like fibers that sprout from cell surface.
- Not involved in locomotion.
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Conjugation pilli
Rigid, tubular structures - pass DNA from cell to cell.
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