Ap Bio Osmosis & Diffusion Lab

Topics: Osmosis, Semipermeable membrane, Cell Pages: 9 (2778 words) Published: November 6, 2012
Stacy Hernandez
Period 1
Mrs. Riley
AP Biology
Osmosis and Diffusion Lab
I. Introduction:
Diffusion is vital to many life functions of a cell, it allow the transportation of vitally important nutrients and compounds without the expenditure of excess metabolic energy. To explain diffusion, it is as if a bottle of perfume is opened at one end of the room, then in a short amount of time a person at the other end of the room can detect the scent of the perfume; this is the process of diffusion. Diffusion is a movement from a higher concentration to a lower concentration. A special kind of diffusion is known as osmosis, osmosis is fundamental in many industrial processes such a water purification, desalination, and waste material treatment. Osmosis is when water is separated by a selectively permeable membrane, with different solute concentrations on either side of the membrane. In osmosis water is moved from regions of low concentration to regions of high solute concentration. Osmosis occurs in both plant and animal cells, across a cell’s plasma membrane. Osmosis also has a major impact on living cells. There are usually more or fewer dissolved particles in one of two compared solutions separated by a membrane, such as cell and the media in which it exists, in environment’s with solute concentrations that match their cytoplasm. When the two solutions on either sides of the membrane are equal and no net movement is detected, the solutions are isotonic. This means that the solutions have the same concentration of solutes. If two solutions differ in the concentration of solutes that each has, the one with more solute is hypertonic. The solution that has less solute is hypotonic. Water potential determines the direction and rate of osmosis. Water potential consists of pressure potential, which is the exertion of pressure on a solution, and osmotic potential, which is the relative concentration of solutes within the two solutions. II. Hypothesis:

Diffusion and osmosis occur between different molar solutions until the solutions are isotonic, effecting the pressure of the plant cells. III. Materials and Procedure:
Per group: In this experiment my group used the following materials: * Four glucose indicator strips
* One graduated cylinder
* 1 plastic cup, 250 ml dialysis tubing, 7ft.
* Six plastic cups, 250 ml
* Glucose starch solution, 15 ml
* IKI (potassium iodide) solution, 1 ml
* Sucrose solution, 0.2 M, 175 ml
* Sucrose solution, 0.4 M, 175 ml
* Sucrose solution, 0.6 M, 175 ml
* Sucrose solution, 0.8 M, 175 ml
* Distilled water
* Paper towels
* Potato
* Plastic wrap
* Microscope slide
* Coverslip
* Compound microscope
* Scalpel
* Forceps
Shared materials:
* Balance
* Compound microscope
* NaCl solution
* Onion epidermis
Part A, Diffusion: We began part A of the experiment by first pouring 15 ml of the prepared glucose/ starch solution into a graduated cylinder. Then we obtained a piece of dialysis tubing that has been soaking in water, and we tied a knot in one end of the tubing. Then we opened the tubing by rubbing the untied end between our fingers, and poured 15 ml of the glucose/ starch solution into the tubing. Then recorded the color of the solution in the bag and noted it in Table 1 in the Analysis section. After, we then determined if glucose was present in the tubing by dipping one of the glucose indicator strips into the solution and then recorded the data in Table 1. Afterward we then carefully tied a knot at the open end of the bag, but left enough space in the bag for expansion. Then we filled a plastic cup approximately 2/3 full with distilled water and added 1ml of potassium iodide to the cup, then recorded the color of the solution in Table 1. After that we determined if glucose was present by dipping another glucose strip into the solution in the beaker and...
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