Wednesday, October 2, 2019

Investigate the Osmotic Point of Equilibrium in a Potato :: GCSE Biology A2 A-Level Coursework

Investigate the Osmotic Point of Equilibrium in a Potato The following Passages are information which I have managed to find when researching the topic of Osmosis: - The cell membrane controls the movement of substances going into and out of the cells. The cell therefore controls the Chemical composition of the internal environment of the cell. It does this in two ways; Passive Process - this does not require energy Active Process - this does require energy to occur This works in principle which diffusion in which molecules and ions in a solution move from an area of high concentration to an area of low concentration resulting in the equal distribution of molecules. Cells membranes are selectively or partially permeable, this means moving the membrane allows certain molecules to pass through it moving freely down the concentration gradient but not others. Osmosis The cell membrane is partially permeable in that it allows some molecules to diffuse rapidly but slows the passing of others. The glucose molecules try to diffuse to the outside but cannot get through the membrane because the pores are too small. The water molecules diffuse trough the pores down the concentration gradient. This membrane- controlled diffusion of water molecuse is controlled by osmosis, it can works both ways so that it can pass into and out of the cell. Osmosis and Diffusion If water is withheld from a flowering plant, the flowers wilt. If bacterial cells are placed in concentrated salt water solution, they collapse and die. Human red blood cells placed in fresh water expand and burst. These are examples of the effects of osmosis, the process by which water passes through a cell membrane. Osmosis is possible because of the constant state of motion that exists at the atomic and molecular levels of matter. Specifically, in liquid solutions, molecules of solute (the dissolved substance) and solvent (the substance, usually liquid, in which the solute is dissolved) move about randomly, spreading from regions of high concentration into regions of low concentration. This process is called diffusion. If a cell membrane allowed an equal passage of solute and solvent, diffusion through the membrane would lead to a cell whose internal composition would be identical to its environment. This does not occur because the cell membrane is differentially permeable, or semipermeable-that is, it is permeable to some molecules but not to others. Water molecules (and dissolved gases such as oxygen and carbon dioxide) pass through the membrane much more readily than dissolved solid solutes, such as sugar and salt (see Cell, "The Cell Membrane"). If the environment is hypertonic (having a higher concentration of solute than the cell), water diffuses out of the cell.

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