Investigating Diffusion: Student Lab Design Cell Membrane: Structure & Function

Word Wall Monomer & Polymer Glucose & Starch Diffusion (Passive Transport) Non-permeable Semi-Permeable Permeable Lipid Bi-layer

Lab Report Handout Please have your Diffusion Lab Word document ready to begin the Experimental Design process for this lab.

Background Information: Animal and plant cells enclose the inside contents of the cell. Membranes are made of two sheets of fat molecules called a phospholipid bilayer. This bilayer is flexible and lets some, but not all, molecules pass through.

Background Information: Carbohydrate Diffusion Glucose and starch are common carbohydrates found in and outside of the average cell. These molecules pass to and from the bloodstream. They diffuse across the membrane based on the rules of passive transport. Glucose Starch

Background Information: Dialysis Tubing The dialysis tubing can be filled up (inflated) by various fluids. The ends will be closed with string in order to prevent leakage of fluid.

“Dialysis Tubing” will be used as the model of the cell membrane “Dialysis Tubing” will be used as the model of the cell membrane. This membrane is similar to a plastic (cellophane) material. This tubing has properties that are similar to real membranes; it’s semi-permeable.

Question What effect does the type of carbohydrate (starch or glucose) have on its diffusion through the membrane? In other words, will glucose and/or starch diffuse through the dialysis tube (bag)? P3 End 10/29/14

Hypothesis Create a hypothesis that predicts whether glucose and/or starch can diffuse (pass through) the dialysis tubing and why (prediction reason).

Experimental Design Experimental Group Control Group tap water MV: 10 mL glucose or starch solution Dialysis tube Cup String tap water Benedict’s Solution Hot plate Or Iodine Control Group ECC: 10 mL water Dialysis tube Cup String tap water Benedict’s Solution Hot plate Or Iodine

Miscellaneous Identify the following items in your lab handout: MV ECC RV CVs (minimum of 3)

Supplies Glucose Solution (for Benedict’s Test) Benedict’s Solution Starch Solution Iodine Solution 10 cm Dialysis Tubing (2) lengths of string (2) Cups Hot Plate (for Benedict’s Test) Water

Group Task Complete the design for this experiment that can show whether glucose or starch can pass through dialysis tubing (a semi-permeable membrane). Complete the following Steps: Follow Procedures and set up experiment Return to your seats when done Data Table (in Data & Observations)

IMPLEMENTING DESIGN

RESULTS DAY

Background Information: Chemical Indicators: Glucose Test Glucose + Benedict’s Solution with heated added (~3 min) = blue. It will gradually turn green and finally become a (burnt) orange color.

Background Information: Iodine Test Starch can be detected by the use of iodine (IKI). Starch + iodine = blue-purple-black color

Carbohydrate Tests: Summary Condition Color with Iodine Test Color with Benedict’s Test + heat Water Yellow Blue Starch (polymer) Purple/Black Glucose (monomer) Orange

Final Day’s Details Throw away the dialysis bags into the trash Please leave the IKI and Benedict’s Solution on the front counter. Discard any liquid waste from the glucose/starch tests into the waste beaker on the front counter.

Diffusion did occur (Yes or No) Data Table Condition Carbohydrate Test: Color Observed Interpretation: Diffusion did occur (Yes or No) MV: Glucose (monomer) Orange Yes ECC: Starch (polymer) Yellow No