LAB #3 - DIFFUSION AND OSMOSIS

Transcription

1 DIFFUSION EXPERIMENT - pg. 4-6 LAB #3 - DIFFUSION AND OSMOSIS Definition of DIFFUSION - The natural tendency of particles to move from areas of high concentration to areas of lower concentration START TIME: 1. Based on your results, indicate on the diagram which circle represents... Potassium Permanganate? Methylene Blue? Note the Molecular Weight of each material on the diagram.(see pg.7) 2. Based on the results, what is the relationship between Molecular Weight and Diffusion Rate? (Circle one): INVERSE DIRECT State the basis of your conclusion 3. Complete all of Questions 5, 6a, & 6b on pages 6 & 7 of the lab manual exercise (DO NOT DO THE MEASURING INDICATED IN QUESTION 6. SKIP QUESTIONS 6c, 7 & 8) 27Sep16 Diffusion & Osmosis Study Guide - Page 1

2 OSMOSIS EXPERIMENT - pg Osmotic Gradients - Definition of Osmosis: A special case of diffusion involving H 2 O diffusing across a selectively permeable membrane Complete THE TABLE below BEFORE COMING TO LAB to summarize the information in Figure 2 page 12 of the lab manual! Use your knowledge of water diffusion to predict whether the model cells will increase or decrease in weight after 1 hour. Hint: Will the net diffusion of water be into the model cell or into the beaker? Cell Letter % solutes inside the model cell % of solutes outside the model cell WILL the model cell increase or decrease in weight after 1 hour Rank the model cells (1,2,3) based on predicted weight change A B C Continues on the Next Page 27Sep16 Diffusion & Osmosis Study Guide - Page 2

3 OSMOSIS EXPERIMENT - pg (con t)! COLLECT THE DATA DURING LAB and COMPLETE THE TABLE ON PAGE 14! Calculate the Net Change for each Model Cell and record it in the Table below! Net Change: Final Weight - Initial Weight! Use the data to create a graph on PAGE 15.! READ PAGE 16 and ANSWER QUESTIONS (p.17)! Answer the following additional question: Using your deductive skills and the results from the Diffusion and Osmosis experiments, which experimental results illustrates a CONTINUOUS GRADIENT and which one illustrates a DISCONTINUOUS GRADIENT? What is the basis of your conclusion? NET CHANGE FOR MODEL CELLS Model Cell 1% Sucrose 25% Sucrose 50% Sucrose Net Change! Does the observed data support your Hypothesis for the ranking of the model cells (Refer to the last column of the table on the preceding page)? If not, why do you think your hypothesis and the observed data differ 27Sep16 Diffusion & Osmosis Study Guide - Page 3

4 INSTRUCTIONS FOR OBSERVATIONS IN LIVING CELLS ***DO NOT USE THE LAB MANUAL INSTRUCTIONS*** PART 1: HYPOTHESIS GENERATION EXERCISE HYPOTHESIS GENERATION - COMPLETE THE TABLE BELOW BEFORE COMING TO LAB Step 1: Use the information on page 16 & 18 to complete the following descriptions. Remember, these terms describe the inside of the cell relative to the outside. Fill in the boxes with LESS, MORE, or THE SAME AMOUNT OF A Hypotonic solution has A Hypertonic solution has An Isotonic solution has SOLUTES than the surrounding environment SOLUTES than the surrounding environment SOLUTES than the surrounding environment WATER than the surrounding environment WATER than the surrounding environment WATER than the surrounding environment ****HYPOTHESIS GENERATION CONTINUES ON THE NEXT PAGE**** 27Sep16 Diffusion & Osmosis Study Guide - Page 4

5 PART 1: HYPOTHESIS GENERATION (continued) Step 2: BEFORE COMING TO CLASS, Generate a HYPOTHESIZED EFFECT (column 2) for what will happen to a living cell (animal or plant) when placed in each of the 3 types of solutions you defined in Step 1. Use your definitions from Part 1 and your knowledge of the principles of diffusion to complete this section There are 3 possible outcomes: (1) The cell is unaffected (2) The cell shrinks or crinkles (3) The cell swells or explodes Solution HYPOTHESIZED EFFECT Complete BEFORE coming to class OBSERVED EFFECT Complete AFTER you do the experiment Was your Hypothesis supported by your Observations? Hypertonic Hypotonic Isotonic 27Sep16 Diffusion & Osmosis Study Guide - Page 5

6 PART 2 - TESTING YOUR HYPOTHESES 1. SECURE 3 COMPOUND MICROSCOPES FOR YOUR GROUP. 2. PREPARE YOUR SPECIMENS ACCORDING TO THE INSTRUCTIONS BELOW. 3. OBSERVE THE CELLS IN EACH SOLUTION 4. RECORD YOUR OBSERVATION IN COLUMN 3 (OBSERVED EFFECT) AND COLUMN 4 IN THE TABLE ON PAGE 5 OF THIS STUDY GUIDE WITH YOUR OBSERVATIONS Osmosis in Animal Cells 1. This experiment uses red blood cells from sheep as an example of an animal cell. 2. Obtain 3 slides from the bowl, wash with tap water and dry thoroughly 3. Prepare 3 wet mount slides! See Lab #2 instructions on preparing wet mounts on page Each wet mount will contain a TINY amount of red blood cells plus 1-2 drops of one of the 3 prepared osmotic solutions (hypertonic, hypotonic, and isotonic). 5. Make sure you keep track of which slide contains which osmotic solution. Osmosis in Plant Cells 1. This experiment uses leaves from a common aquarium plant, Elodea 2. Obtain 3 slides from the bowl, wash with tap water and dry thoroughly 3. Prepare 3 wet mount slides! See Lab #2 instructions on preparing wet mounts on page Each wet mount will contain a single Elodea leaf plus 1-2 drops of one of the 3 prepared osmotic solutions (hypertonic, hypotonic, and isotonic). 5. Make sure you keep track of which slide contains which osmotic solution. 27Sep16 Diffusion & Osmosis Study Guide - Page 6