This creates hydrostatic pressure - turgor. As mentioned above, the water there pushes the cytoplasm outward against the cell wall. You can imagine that the solution and the cell have equal concentrations, so there is no net movement of water molecules into or out of the cell.The central vacuole of a plant has a crucial role. The cell swells!įinally, an isotonic solution is one that causes no change in the cell. In this case, you can imagine that the solution is less concentrated than the cell’s cytoplasm, causing water from the solution to flow into the cell. If a solution is hypotonic to a cell, then the cell will swell when placed in the hypotonic solution. If a cell shrinks when placed in a solution, then the solution is hypertonic to the cell. This will cause water from the cytoplasm to leave the cell, causing the cell to shrink. Though it certainly is more complex than this, for our purposes in this class, we can assume that a hypertonic solution is more concentrated with solutes than the cytoplasm. Ultimately, the tonicity of a solution can be determined by examining the effect a solution has on a cell within the solution.īy definition, a hypertonic solution is one that causes a cell to shrink. The tonicity of a solution involves comparing the concentration of a cell’s cytoplasm to the concentration of its environment. Osmosis is the movement of water across a semipermeable membrane (such as the cell membrane). After 10 minutes, observe the color changes in the two bags and the external solutions. Let diffusion occur between the bags and the solutions in the beakers.Place this bag containing the starch solution into beaker #2. Again seal the bag tightly and rinse as above. Add 10 ml of starch solution to the other dialysis tube.Thoroughly rinse the bag containing phenolphthalein, then place it in into the beaker containing the NaOH.Seal the other end of the bag by carefully folding and tying as before. Add 10 ml of water and three drops of phenolphthalein to one of your dialysis tube bags.It is critical that your tubing is tightly sealed, to prevent leaks. Tie the folded portion of the tube securely with string. Now prepare your 2 dialysis tubing “bags.” Seal one end of each dialysis tube by carefully folding the end “hotdog style” 2 times, then “hamburger style” 1 time.Fill beaker #2 with 300 ml of tap water, then add iodine drops drop by drop until the solution is bright yellow.Do not spill the NaOH-it is very caustic! Fill beaker #1 with 300 ml of tap water, then add 10 drops of 1 M NaOH.Using a wax pencil, label one beaker #1.The rate of diffusion is influenced by both temperature (how fast the particles move) and size (how big they are). As these atoms/molecules bounce off each other, the result is the movement of these particles from an area of high concentration to an area of low concentration. The movement of particles due to this energy is called Brownian motion. (In fact, you can quantify the kinetic energy of the atoms/molecules in a substance by measuring its temperature.) The moving atoms bounce off each other, like bumper cars in a carnival ride. It is this kinetic energy that makes each atom or molecule vibrate and move around. All atoms and molecules possess kinetic energy, which is the energy of movement. How does the cell carry out these seemingly paradoxical roles? To understand this process you need to understand the makeup of the cell membrane and an important phenomenon known as diffusion.ĭiffusion is the movement of a substance from an area of high concentration to an area of low concentration due to random molecular motion. The cell membrane plays the dual roles of protecting the living cell by acting as a barrier to the outside world, yet at the same time it must allow the passage of food and waste products into and out of the cell for metabolism to proceed.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |