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Unformatted text preview: 2-15Movement of Substances-dependant on the chemical potential energy of the substanceA. Energy= the ability to do work (work: the displacement of a substance against a force)B. Types of movement:1. Spontaneous-movements from a sight of higher to one of lower potential energy for the substance (dropping a pen, waterfall)2. Non-spontaneous-movements are from a site of lower to one of higher potential energy *requires an input of energyC. Chemical Potential Energy determined by:1. Amount-more molecules = higher potential energy 2. Temperature- higher temperature = higher potential energy (measure of molecular motion, 0K no molecular motion)3. Pressure-more pressure = higher potential energy4. Gravity- higher up, greater chemical potentialD. Water Movementdependant on the chemical potential energy of water () at 2 points (a gradient)waterfall example: higher and lower , same amount, same pressure, same temperature, gravity different (big difference)water alwaysmoves spontaneously in plants is basically determined by:oamount (purity) higher solute, lower purity, lower oa solution has a lower than waterowall pressure, if inside a parenchyma cellmovement in and out of a cell-changes in the amount of water and wall pressure determine changes in the of the cell waterInto a cell (parenchyma) plants cells do, animal cells dontowill not occur foreverowhen out= inno net movement oincrease indue to increase in amount of H2Oowater goes from higher to lower 2-17When water is moving out of the cell:1. Water potential is higher inside the cell than outside(e.g., water evaporating from mesophyll cell surfaces).2. Water moves out of the cell, reducing the water pressure on the wall, so the wall pressure goes down, as well.3. The lowering of the pressure and the loss of water from the cell lowers its water potential, which will continue until the water potentials on both sides of the cell membrane become equal.Water moving in the xylem from roots to leaves1. During the day, water moves into a plant in response to a lowering of the water potential in the plant below that of the soil water, which is usually rather high.a. This development occurs in the morning on most days.2. Stomata are opened by guard cells in response to light shining on the leaf.3. Since the water potential of the water vapor in the air outside of the leaf is less thanthat of the water in the leaf air, water moves out of the leaf air via stomata.a. The water potential of water vapor is dependent onthe RELATIVE HIMIDITY of the air (amount of water in the air relative to what it could hold at a given temp.). 100% R.H. = air saturated with waterb. R.H. of the leaf airis usually maintained at close to 100%. The atmospheric R.H....
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This note was uploaded on 11/14/2010 for the course BIOL 1401 taught by Professor Holaday during the Spring '08 term at Texas Tech.
- Spring '08