Membrane Permeability r1.04

The Snapshot button is used to capture the screen. The Journal is where snapshots are stored and viewed. The Share button is used to export or print your journal to turn in your work. Introduction Journals and Snapshots Membrane Permeability Each page of this lab that contains the symbol should be inserted into your journal. After completing a lab page with the snapshot symbol, tap (in the upper right hand corner) to insert the page into your journal. Note: You may want to take a snapshot of the first page of this lab as a cover page for your journal.

Lab Challenges What types of substances are able to pass through a semi-permeable membrane? Membrane Permeability

Background The contents of a cell are separated from the outside environment by a membrane. The cell membrane, also called plasma membrane, consists mostly of phospholipids and proteins. Phospholipids have 2 distinct regions: a hydrophilic head and a hydrophobic tail. They form a bilayer by arranging themselves tail to tail, so only their hydrophilic heads are exposed to the aqueous environment inside and outside the cell. Membrane Permeability

Self Check 1.Phospholipids arrange themselves in a bilayer because they have ____________________. a)hydrophobic tails and hydrophilic heads b)hydrophilic tails and hydrophobic tails c)opposite charges d)bipolar DNA Membrane Permeability This image is a reminder to tap to take a snapshot of the page after you have entered your response. Self Check

...Background In some cases, the cell membrane acts as a passive barrier and substances can move in and out of the cell based on concentration gradient. Water, carbon dioxide, oxygen, cholesterol and other small polar molecules are able to diffuse passively across the membrane. In other cases the membrane can be very selective about what is able to enter and leave. Substances that cannot diffuse through the membrane must pass through a protein channel. Some protein channels act as an open gateway that specific substances can pass through. Other protein channels require energy input and act as pumps to move substances against the concentration gradient. Membrane Permeability

Self Check 2.Substances that cannot diffuse directly through the phospholipid bilayer but go through a(n) ____________. a)ion gate b)water pore c)carbohydrate chain d)protein channel Membrane Permeability Self Check

Safety Use all standard laboratory safety procedures. Wear safety glasses and lab coats or aprons. Dispose of chemicals and solutions as instructed. Membrane Permeability

Materials and Equipment Collect all of these materials before beginning the lab. pH sensor Beaker, 250 mL Large Base and Support Rod Utility clamp (2) Lugol's Iodine 0.1 M Hydrochloric Acid 0.1 M Sodium Hydroxide Starch Solution Dialysis Tubing, 15cm length (2) Magnetic stirrer and stir bar Wash Bottle Distilled Water Binder clip String Membrane Permeability

The steps to the left are part of the procedure for this lab activity. They are not in the right order. Determine the correct sequence of the steps, then take a snapshot of this page. Sequencing Challenge A. Record data and then determine the change in pH for each data run. B. Lower the dialysis tubing into the water. C. Prepare the dialysis bags. D. Add distilled water to the beaker and turn on the magnetic stirrer. Membrane Permeability

Setup: Dialysis Bags (HCl and Starch) 1.Tie one end of one piece of dialysis tubing with string to create a bag. Rub the tubing between your fingers to open the top of the bag. 2.Pour 15 mL of 0.1 M HCl (hydrochloric acid), and 5 mL of the starch solution into the bag. Note: Wash your hands. The oils on your skin can clog the pores of the tubing. Caution: HCl is corrosive and can ruin clothing, and cause skin and eye irritation. Notify your teacher of any skin/eye contact. 3.Fold over the open end of the bag and use a binder clip, or string, to secure it shut. Membrane Permeability

Setup: Dialysis Bags (NaOH) 4.Tie one end of a second piece of dialysis tubing with string to create a bag. Rub the tubing between your fingers to open the top of the bag. 5.Pour 15 mL of 0.1 M NaOH (sodium hydroxide). Caution: NaOH is corrosive and can ruin clothing, and cause skin and eye irritation. Notify your teacher of any skin/eye contact. 6.Fold over the open end of the bag and use a binder clip, or string, to secure it shut. 7.Rinse both bags under a gentle stream of water and place aside on a labeled paper towel. Membrane Permeability

Setup: Hydrogen Ions 1.Connect a pH sensor to the SPARK Science Learning System. 2.Place a spin bar into a 250 mL beaker and place the beaker on the magnetic stirrer. 3.Use a base, support rod and clamp to position the pH probe low in the beaker, but not touching the stir bar. 4.Use a second clamp to suspend the dialysis bag containing the HCL and starch above the beaker. 5.Add 100mL of water and 25 drops of Lugol's iodine to the beaker. Adjust the pH probe so it is in the water. Membrane Permeability

Q1: What will happen to the pH in the beaker when the HCl bag is lowered into it? Draw your prediction on the graph provided*. *To Draw a Prediction: 1.Tap to open the tool palette. 2.Tap then use your finger to draw your prediction. 3.Tap when finished. 4.If you make a mistake, tap to clear your prediction. Membrane Permeability

Q4: Will the iodine molecules move into the bag? How will you know if they do? Q3: Will the starch molecules move out of the bag? How will you know if they do? Q2: Will the hydrogen ions move out of the bag? How will you know if they do? Membrane Permeability

Collect Data: HCl 1.Turn on the magnetic stirrer. 2.Tap to start collecting data. 3.Wait 60 seconds and lower the dialysis bag into the water. 4.After 300 seconds, tap to stop data collection. Membrane Permeability

5.Enter any color change observations in the data table.* *To Enter Data into a Table: 1.Tap to open the tool palette. 2.Tap then tap a cell in the data table to highlight it in yellow. 3.Tap to open the Keyboard screen. Membrane Permeability

Setup: Hydroxide Ions 1.Dispose of the HCl bag and clean out the 250 mL beaker. 2.Place a spin bar into the beaker and place the beaker on the magnetic stirrer. 3.Use a base, support rod and a clamp to position the pH probe low inside the beaker, but not touching the stir bar. 4.Use a second clamp to suspend the dialysis bag containing the NaOH above the beaker. 5.Adjust the pH probe so it is in the water. Membrane Permeability

Q5: What will happen to the pH in the beaker when the NaOH bag is lowered into it? Draw your prediction in the graph*. *To Draw a Prediction: 1.Tap to open the tool palette. 2.Tap then use your finger to draw your prediction. 3.Tap when finished. 4.If you make a mistake, tap to clear your prediction. Membrane Permeability

Collect Data: NaOH 1.Turn on the magnetic stirrer. 2.Tap to start collecting data. 3.Wait 60 seconds and lower the dialysis bag into the water. 4.After 300 seconds, tap to stop data collection. Membrane Permeability

Data Analysis Membrane Permeability 1.Determine initial pH, final pH and the change in pH for each run.* Note: Enter these values on the next page. * To Find the X- and Y- Values of a Data Point: 1.Tap to open the tools palette. 2.Tap and then tap a data point. 3.Tap or to select nearby data points.

Data Analysis 2.Record initial pH, final pH, and the change in pH for each run in the table. *To Enter Data into a Table: 1.Tap to open the tool palette. 2.Tap then tap a cell in the data table to highlight it in yellow. 3.Tap to open the Keyboard screen. Membrane Permeability

Analysis 1.Describe what happened to the pH in the beaker during the soaking of the HCl bag. What does this indicate about the permeability of H+ ions to the membrane? Membrane Permeability

2.Describe what happened to the pH in the beaker during the soaking of the NaOH bag. What does this indicate about the permeability of OH- ions to the membrane? Membrane Permeability Analysis

3.Describe what happened between the starch and iodine. Was iodine abe to move into the bag? Was starch able to move out of the bag? Explain your answer and support it with data. Membrane Permeability Analysis

4.This lab is demonstrating diffusion and semi-permeable membranes. Define these concepts. Membrane Permeability Analysis

Synthesis 1.How could the diffusion rate be increased? Membrane Permeability

2.How could you use a series of molecules to determine the size of the pores in the membrane? Membrane Permeability Synthesis

3.How does this membrane model differ from a real cell membrane? What structures are present in a real cell membrane that regulate what can enter and exit the cell? Membrane Permeability Synthesis

4.Does this model illustrate active or passive transport? Explain your answer. Membrane Permeability Synthesis

Multiple Choice 1.Despite differences in cell types, all cells have a _________________. a)cell wall b)cell membrane c)golgi apparatus d)endoplasmic reticulum Membrane Permeability

Multiple Choice 2.The membrane of a cell will allow water, oxygen, carbon dioxide, and glucose to pass through. However, other substances are blocked from entering. This type of membrane is called: a)semi-permeable b)perforated c)permeable d)non-permeable Membrane Permeability

Multiple Choice 3.Cell membranes are constructed mostly of a)protein channels. b)carbohydrate channels. c)lipid bilayers. d)hydrophobic regions Membrane Permeability

= starch = glucose Multiple Choice 4.Look at the diagram to the right and choose the correct statement. The membrane is permeable to glucose, but not permeable to starch a)Glucose will move from right to left. b)Starch will move from right to left. c)Salt will move from right to left d)No molecules will move in any direction. Membrane Permeability

You have completed the lab. Congratulations! Please remember to follow your teacher's instructions for cleaning-up and submitting your lab. Membrane Permeability

Images are taken from PASCO documentation, public domain clip art, or Wikimedia Foundation Commons References Membrane Permeability