Investigating Investigating DiffusionDiffusion: 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. 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)?

Hypothesis

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

Experimental Design

Experimental Group MV: 10 mL glucose or

starch solution Dialysis tube Cup String tap water

Benedict’s Solution Benedict’s Solution Hot plateHot plateOrOr IodineIodine

Control Group ECC: 10 mL water Dialysis tube Cup String tap water

Benedict’s Solution Benedict’s Solution Hot plateHot plateOrOr IodineIodine

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 TestGlucose + 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 Blue

Glucose (monomer) Yellow 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.

Data TableCondition Carbohydrate

Test: Color Observed

Interpretation:Diffusion did

occur (Yes or No)

MV: Glucose (monomer)

Orange Yes

ECC: Starch (polymer)

Yellow No