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Cell Biology P3 (Origins of Cells (Endosymbiotic Theory:
Larger cell…
Cell Biology P3
Origins of Cells
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Cells are formed by division of pre-existing cells; before cells there were only non-living materials
Pasteur’s Experiments:
Use of swan-necked flasks
Samples of broth in flasks with long necks then melted glass of necks and bent it into various shapes
Boiled the broth in some flasks to kill microorganisms and left others un-boiled (as controls)
Fungi + other organisms appeared in un-boiled flasks
Broth in flasks were in contact with air, apparently needed for spontaneous generation
So he snapped necks of some flasks to leave shorter neck
Ogranisms found in these flasks
Conclusion: Swan necks prevented organisms from getting air and no organisms appeared spontaneously
Endosymbiotic Theory:
Larger cell takes in smaller cell by endocytosis in a vesicle, so smaller cell performs useful function for the larger cell
Smaller cell divides as frequent as larger cell does
Occurred in origin of eukaryotes
Mitochondrion:
Cell respiring anaerobically took in bacterium respiring aerobically
Bacterium made ATP for itself and host cell, making it more efficient for host cell
Aerobic bacterium evolved into mitochondrion and large cell evolved into heterotrophic eukaryotes (animals)
Chloroplast:
Heterotrophic cell took in photosynthetic bacterium
Bacterium supplied larger cell with organic compounds, so now autotroph
Bacterium evolved into chloroplast and host cell evolved into photosynthetic eukaryotes (plants)
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Osmosis
Passive movement of water molecules from a region of low solute conc. to a region of high solute conc. across a partially permeable membrane
Estimating Osmolarity: The number of moles of solute particles per unit volume of solution
Plants absorb water from surrounding if surrounding solution is hypotonic (lower conc), or lose water if surrounding is hypertonic (high conc)
Avoiding Osmosis in Donor Organs:
Donor organs must be bathed in isotonic saline which is same osmolarity as human cytoplasm (avoid gain/loss of water by osmosis and tissues/organs swelling/shrinking up)
Donor organs surrounded by isotonic slush when being transported with low temp (keep them healthy)
Active Transport
Movement of substances from region of low conc. to region of high conc. against its conc. gradient through a partially permeable membrane using energy from ATP
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