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

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

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

4. 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.

5. 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

6. 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.

7. “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.

8. 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

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

10. 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

11. Miscellaneous Identify the following items in your lab handout: MV ECCRV
CVs (minimum of 3)

12. 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

13. 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)

14. IMPLEMENTING DESIGN

15. RESULTS DAY

16. 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.

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

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

19. 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.

20. 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