Objective(s): The main purpose is to find out if plastic bags are permeable to starch and, or, iodine. Also, to find out wither potatoes are hypotonic, hypertonic, or isotonic by testing the different amounts of sucrose solutions
Introduction: The necessary background information needed for this lab is the definition of osmosis, diffusion, active transports, passive transports, permeability, concentration, tonicity, and to now the scientific concepts of hypotonic, isotonic, and hypertonic.
Hypothesis: For part 1 my hypothesis is: That the starch will diffuse across the plastic bag and react with the iodine and will have a color change to the water to imply the reaction happened. For part 2 my hypothesis is: that the potatoes will be hypotonic in the sucrose solutions, while in water the potatoes and sweat potato will be isotonic. Also the sweat potato, will be hypotonic. Procedure: For part one the control group is the plain bowl with water, and then the independent variable is the permeability of the plastic bag, and the dependent variable is the change of color in the water. Part 1: Cell Membrane and Permeability 1. Create a starch solution in a bowl or cup by one of the following methods: • Option 1. a. Add 1/4 cup cornstarch and 1/4 water into a bowl. b. Stir to mix. c. Add 1 to 1 1/2 cups very warm water (be very careful when working with hot water) and stir well. • Option 2. a. Boil a small potato in 2 cups of water b. Mash the potato c. After the potato cools, pour water over the mashed potato and strain the fibrous part out using a coffee filter. d. Be sure to cool to room temperature to avoid adding temperature as a variable. 2. Add starch solution: . Measure out 1 cup of the starch solution and pour carefully into one sandwich bag. a. Zip lock the sandwich bags tightly to prevent leaks-leaving some air in the bag above the starch solution. b. Test for leaks to ensure that the bags are sealed tightly. c. If any of the solution leaks, try reinforcing the bag by twisting and tying with a string. 3. Rinse the outside of the sealed bag with water and blot dry with a paper towel. 4. Repeat steps 2 and 3 with plain water for the second sandwich bag. 5. Fill the two large cups or bowls half-full with water. 6. Label each cup based on the contents of the bag it will contain: "starch" and "water." 7. Add three drops of iodine into each cup of water and stir. Observe and record the initial color in your data table. 8. Carefully place each bag in the appropriate cup of water/iodine solution. 9. Record your hypothesis about what you expect to observe in each cup. Be sure to include a justification for your hypothesis. 10. After 30 minutes, observe the bags and surrounding water for any color change. • Iodine and …show more content…
We can use this explain the change of color being due to the exchange of electrons going on when the starch and iodine connected.
6. If a balance was available, describe how you could use it in this experiment and what the purpose would be.
If there was a balance than you could use it in the experiment to show that an isotonic state is available.
7. Living organisms are made of cells. Those cells must receive nutrients and gases in order to undergo the metabolic processes that maintain homeostasis. In paragraph form, explain how you think the nutrients and gases enter the cell. Distinguish between the molecules that can enter by diffusion by simply moving across the membrane and those that must expend energy to cross the cell membrane.
Nutrient and gasses can enter a cell thru a multitude of ways. One way for small non polar molecules is that they can easily pass through the phosphide bilayer, since it has selective permeability. Also water can pass through with the attraction it has with the hydrophilic head of the phosphides. Passive transport of small molecules can also be possible along with the passive transport of large molecules can happen due to carrier