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September 11-ch 5 - o With adequate turgor pressure vacuole...

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September 11, 2007 Chapter 5 Passive Transport Osmosis: the special case of water diffusion o From high concentration to low concentration o Dissolved substances reduce the concentration of free water molecules in a solution Hypertonic o More dissolved solutes o Less water Hypotonic o Fewer dissolved solutes o More water Osmosis explains why fresh water protists have contractile vacuoles o Water leaks in continuously because the cytosol is hypertonic fresh water o Salts are pumped into the vacuoles, making them hypertonic to the cytosol o Water follows by osmosis and is then expelled by contraction Turgor pressure in plant cells o Vabuole filled with solutes Hypertonic to cytosol Cytosol hypertonic to extracellular fluid
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Unformatted text preview: o With adequate turgor pressure, vacuole pushes against cell walls, maintaining cell’s shape o In absence of water, cells collapse Active Transport o Cells need to move some substances against concentration gradients o Requires ATP (energy) to do so o Membrane proteins move molecules across using ATP o Endocytosis o Moving things into a cell (water, minerals, energy) o Exocytosis o Moving things out of a cell (waste, hormones, etc) Cell Size and Shape o As a cell grows, it has less membrane to engage in less cellular activity o Specialized Jucnitons o Desmosomes attach cells together o Tight junctions make cell attachments leak proof o Gap junctions (animals)...
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