Diffusion ­ is the movement of any molecule in response to a concentration gradient. That is any molecule will "diffuse" from an area of high concentration to low concentration. If the molecule is too big to pass through the membrane (like sugar, protein....), then water will move into the concentrated solution to try to dilute it.
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Vinegar is only about 3% acetic acid (relatively dilute) ­ once the egg shell was gone, the egg membrane is permeable to water but not to the big proteins and fats that make up the interior. The egg increased in mass and volume in the vinegar because of osmosis ­ water moved into the egg from the vinegar solution in response to high concentration of fats and proteins. The contents of the egg are hypertonic to the vinegar. So water from the aqueous solution of vinegar moved into the egg to increase the mass and volume.
Then we put the egg in corn syrup ­ the corn syrup is HIGH concentration (hypertonic)­ must be higher concentration than the proteins in the egg. The sugar that makes the corn syrup concentrated is too big to pass through the membrane, the proteins are too big to pass through membrane. Water moved from the hypotonic egg to the corn syrup.
In third step, we took the shriveled egg from corn syrup and put it in pure water.
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You conduct an experiment to demonstrate movement of molecules through a membrane. You remove the egg shell from an egg and alternate the following solutions. Explain these results (hypertonic, hypotonic, isotonic, concentration, solute, solution, permeable, semi­permeable):
Original mass ­ 64.6 g
After vinegar ­ 81.3 g
After corn syrup ­ 45.6 g
After water ­ 90.8 g
If a solution is dilute ­ it means it has low solute concentration but high water concentration. If a solution is concentrated it has high solute concentration but low water concentration so water is moving by simple diffusion. Water will move from dilute solution to a concentrated solution in osmosis.
The egg gained mass after the shell was dissolved by acidic vinegar because the egg membrane is now permeable to water. Water moved into the more concentrated (hypertonic) interior of the egg from the dilute (hypotonic) vinegar by osmosis. And the big molecules (protein and fats) that make up interior of egg could not pass through the membrane of the egg. Osmosis often occurs when a solute cannot pass through a barrier but water can. When we soaked the egg in corn syrup, the mass decreased because the corn syrup was more concentrated (hypertonic) in solute (less water) than the interior of egg (more water). Putting the shriveled egg into pure water (more water in pure water than in the egg). The egg increased in mass because the water moved to the more concentrated interior of the egg.
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Mass
Original
64.27g
After Vinegar
88.6 g
After Corn Syrup
49.9 g
After water
90.2 g
Circumference
The first gain of mass for the egg was because the egg which is highly concentrated inside with proteins and fats was in a 3% solution of vinegar (relatively dilute ­ less concentrated). Osmosis is the movement of water from areas of dilute concentration (hypotonic) to areas of high concentration (hypertonic). The loss of mass in corn syrup was because the corn syrup was hypertonic to the interior of the egg (hypotonic), so water moved from egg to corn syrup and lost mass.
In pure water, the egg was hypertonic to the pure water so water moved into the egg. Water moves from hypotonic regions to hypertonic regions if the solute can't move. 4
Passive transport means no energy involved! It is a movement of molecules towards equilibrium ­ will always occur in response to a concentration gradient. That is, it moves from high to low concentration.
Passive transport will occur through a barrier IF that barrier is permeable to the molecule in question. That may happen for small molecules across membranes (ions, water, some small polar molecules). For larger molecules it can still happen through carriers or channels ­ facilitated diffusion. Sometimes a molecule just can't get through so osmosis may occur. For example, if you soak a swollen limb in a high concentration of epsom salts, the concentrated solution will pull water out of your swollen ankle. Osmosis is the diffusion of water.
Active transport uses energy (ATP) ­ why, why, why???? Moves molecules against the concentration gradient ­ in other words you are moving molecules from low to high concentration. Why does a cell want to do this???? Cells are building potential energy by creating a concentration gradient. Like water being stored behind a hydroelectric dam and then being released to make electricity. 5
Describe the structure of a water molecule and explain in depth how that structure determines at least 3 critical properties of water that contribute to maintenance of life on our planet.
Water is H2O and has polar covalent bonds because oxygen is more electronegative than hydrogen (everything is more electronegative than hydrogen because hydrogen only has 1 proton) ­ but oxygen (also nitrogen) are particularly electronegative which means they pull the electrons more closely their side of the bond. Hydrogen end becomes slightly + and the oxygen end is slightly ­. Water is a bent molecule so the hydrogen end can be considered on a different side than the oxygen end. For example, water can absorb a lot of heat without changing temperature. The hydrogen bonds of the water want to hold them in roughly same position. Temperature is a measure of activity/movement of molecules. Because water has somewhat stable hydrogen bonds you have to add more heat energy to get the molecules to significantly change their movement which is then temperature. In sweating, the heat to actually evaporate the water from your skin comes from your own body so it is removing heat energy from your body.
Likewise capillary action is when water clings or moves across another substance like a paper towel ­ the hydrogen bonds help the water crawl across a material. Your rain jacket is nonpolar so it will not attract the water.
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