Grand Canyon University
BIO-100L Biology Concepts
September 16, 2011
Use the information below to complete the Osmosis Experiment. Materials
1 fresh baking potato
Four small containers (i.e., drinking cups or clear glasses) A metric ruler
Methods and Procedure
1) Place 1 cup (236 ml) of water in each of the 4 containers. In 2 of the containers, add 1 tablespoon (14.8 ml) of table salt and mix well until dissolved. Label which containers have salt. Cut a fresh baking potato into 5 mm slices. Cut four rectangles 2.5 cm x 1 cm from the slices as close to the same size as possible. Measure the length and width of each rectangle in metric units and place one in each of the containers, keeping track of which measured slice went in which container. There will be two slices (duplicates) for fresh water and two for salt water. After 1 hour, remove and measure the length and width of each piece of potato and return it to the appropriate container. Note any physical changes. After 24 hours, remove and measure the length and width of each piece of potato. Note any physical changes in the potatoes and describe their appearance. Written Lab Report
1) Address the following questions:
A) Define osmosis. Osmosis is the movement of solvent molecules through a selectively permeable membrane into a region of higher solute concentration, aiming to equalize the solute concentrations on the two sides. It may also be used to describe a physical process in which any solvent moves, without input of energy, across a semi permeable membrane (permeable to the solvent, but not the solute) separating two solutions of different concentrations. Although osmosis does not create energy, it does release kinetic energy  and can be made to do work,  but is a passive process, like diffusion. (en.wikipedia) (2011-09-16) Osmosis is the passage of water from a region of high water concentration through a semi-permeable membrane to a region of low water concentration. (Purchon) (n.d.) 1. Semi-permeable membranes are very thin layers of material (cell membranes are semi-permeable) which allow some things to pass through them but prevent other things from passing through.
Cell membranes will allow small molecules like Oxygen, water, Carbon Dioxide, Ammonia, Glucose, amino-acids, etc. to pass through. Cell membranes will not allow larger molecules like Sucrose, Starch, protein, etc. to pass through. 2. A region of high concentration of water is either a very dilute solution of something like sucrose or pure water. In each case there is a lot of water: there is a high concentration of water.
Some teachers use the definition which starts "Osmosis is the passage of water from a dilute solution to a......" this means exactly the same as the definition I have given. 3. A region of low concentration of water is a concentrated solution of something like sucrose. In this case there is much less water.(Purchon)(n.d.) * b) State a prediction for each experiment (both salt and fresh water). *
* To find out what the solute concentration of a potato is, I will find out the effect of Osmosis on a potato. If there is more water outside the potato than inside of the potato, the potato will increase in size. If there is less water outside of the potato than inside the potato, the potato will decrease in size. (Purchon) (n.d.) * How will the potato change when adding salt to the water? * Water that has different concentrations will have an affects on the potato when it is placed into the water. Potato cells have water in them, giving them the ability of Osmosis *
* Hypertonic- The concentration of water is higher inside the cell than outside the cell, more water will be flowing out of the cell than into the cell. * Hypotonic- The concentration of water is higher outside the cell than inside of the...