Biology Unit 5 Cancer, Lab Activity 5-2

Transcription

1 Biology Unit 5 Cancer, Lab Activity 5-2 The Plasma membrane serves as a barrier between the internal cell environment and the external world. The plasma membrane is a dynamic structure. It allows some substances through while excluding others. All molecules move by diffusion. Diffusion is the movement of molecules from high concentration to low concentration. Osmosis is the process by which water moves across the membrane from a high concentration of water to a low concentration of water. Osmosis is a special case of diffusion. In this experiment you will explore the nature of the plasma membrane, diffusion, and osmosis. Research Question What molecules can get into and out of cells? Protocol (both of these activities are to be done as a lab group of four) ctivity 1 - Diffusion Diffusion is the random movement of molecules from an area of greater concentration to an area of lesser concentration. Diffusion is why odors spread out in a room even when the air is not moving. A Step 1 ) In this step you will use a model cell membrane to determine the relative size of several molecules. Use Wikipedia to find an article on the cell membrane in order to get a visual model and to complete illustration 1. Answer Stop questions #1-2 before continuing A diffusion. ctivity 2 Osmosis Osmosis is the movement of water across a membrane by the process of Step 2) In this step you will be determining the concentration of the interior of a cell using osmosis. Osmosis is diffusion of water across a semi permeable membrane. What this means is that we are concerned with how well water moves across a membrane. The important thing to remember is that we are concerned with water movement, not the movement of other molecules. Answer Stop questions #3-4 before continuing Lab5-2,Cancer,CellMembranesStudentLabPacket2013 Greg Ballog 2013 Page 1 of 9

2 Write a step by step protocol for Activity 1 Lab5-2,Cancer,CellMembranesStudentLabPacket2013 Greg Ballog 2013 Page 2 of 9

3 Write a step by step protocol for Activity 2 Lab5-2,Cancer,CellMembranesStudentLabPacket2013 Greg Ballog 2013 Page 3 of 9

4 Flow Chart Lab 5-2 Activity 1 Manipulated Variable: Responding Variable: Controlled Variable #1 Controlled Variable #2 Lab5-2,Cancer,CellMembranesStudentLabPacket2013 Greg Ballog 2013 Page 4 of 9

5 Flow Chart Lab 5-2 Activity 2 Manipulated Variable: Responding Variable: Controlled Variable #1 Controlled Variable #2 Lab5-2,Cancer,CellMembranesStudentLabPacket2013 Greg Ballog 2013 Page 5 of 9

6 Data Data Table 1: Osmosis and Dialysis (+) means present (-) means absent Water Iodine Glucose Starch Model Cell Initial (+ or -) Final (+ or -) Beaker Initial (+ or -) Final (+ or -) Illustration 1 - Model Cell (visual representation of Data Table 1) Show where the different molecules began the experiment and then draw arrows to show where they were at the end of the experiment. Lab5-2,Cancer,CellMembranesStudentLabPacket2013 Greg Ballog 2013 Page 6 of 9

7 Data Table 2: Potato Core: Individual Data Contents in Beaker Initial Mass Final Mass Mass Difference Percent Change in Mass* a) Distilled Water b) 0.2 M Sucrose c) 0.4 M Sucrose d) 0.6 M Sucrose e) 0.8 M Sucrose f) 1.0 M Sucrose *To calculate: Percent Change in Mass = Final Mass Initial Mass x 100 Initial Mass Distilled Water 0.2 M 0.4 M 0.6 M 0.8 M 1.0 M Data Table 3: Potato Core Results: Class Data % change in mass Total Attach LoggerPro graph of Potato Core data here Graph 1 Potato Core Mass Change Class Average Lab5-2,Cancer,CellMembranesStudentLabPacket2013 Greg Ballog 2013 Page 7 of 9

8 Stop Questions 1) What is diffusion? 2) The dialysis tubing is semi-permeable. What does semi-permeable mean? 3) What is osmosis? 4) Why should the containers with the potato cores be covered overnight? Graph Analysis What is the molarity (molar concentration) of the potato cells? To answer this you must read your data from the graph. This answer must agree with the graphed data +25 points, -50 if unanswered or incorrectly interpreted from graph. Have your teacher check and stamp your answer before turning this lab packet in. Analysis Questions 1) In the diffusion experiment (step 1) which substance(s) are: Entering the bag Leaving the bag 2) What experimental evidence supports your answer to question #1? Entering evidence Leaving evidence 3) Based on your observations in the diffusion experiment (step 1), rank the following (glucose molecules, water molecules, IKI molecules, membrane pores, starch molecules) by relative size, beginning with the smallest: Smallest 4) What results would you expect if the diffusion experiment (step 1) started with a glucose and IKI solution inside the bag and only starch and water outside? State as a hypothesis. I expect because 5) What characteristic of the model membrane allows substances to move in and out of the model cell? 6) Why does water move in or out of the potato cores? 7) Why does water eventually stop moving into the potato cores? 8) Why did we combine each group s data? Lab5-2,Cancer,CellMembranesStudentLabPacket2013 Greg Ballog 2013 Page 8 of 9

9 Conclusion Draw pictures showing what will happen when the given model cells are placed in the following environments: Beaker Cell- Internal solute concentration Beaker - External solute concentration A 7% 25% B 7% 7% C 7% 5% Make one drawing for each situation and include six arrows in each beaker to show which way water will move. Below each drawing tell whether the cell will shrink or grow A B C Illustration 2-Cell Membrane (Color and label your drawing not a cut and paste) Lab5-2,Cancer,CellMembranesStudentLabPacket2013 Greg Ballog 2013 Page 9 of 9