biology

Cell Membrane Transport

Hands-On Labs, Inc. Version 42-0034-00-01

Lab RepoRt assistant This document is not meant to be a substitute for a formal laboratory report. The Lab Report Assistant is simply a summary of the experiment’s questions, diagrams if needed, and data tables that should be addressed in a formal lab report. The intent is to facilitate students’ writing of lab reports by providing this information in an editable file which can be sent to an instructor.

Exercise 1: Diffusion through an Artificial Membrane

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Data Table 1: Changes During Dialysis
Color	Before Dialysis	After Dialysis
Solution in cup 1
Solution in dialysis tubing

Data Table 2: Benedict’s Reagent Results
Color of Solution	Before Heating	After Heating
IKI solution in cup 1
Solution in dialysis bag in cup 2
Distilled water

( E x p e ri m e n t ) ( C e l l M e M b r an e T r an s p o r T )

( 75 ) ( © H a nds-On L a bs, I n c . ) ( w w w . L a b P a q . c o m )

Questions

A. What is the purpose of this exercise? What is being tested?

B. What color change did you observe in the dialysis tubing? What does that change indicate? C. Was there a color change in the water surrounding the tubing? If so, explain.

D. What color change did you observe in the water containing the IKI after heating? What does that change indicate?

E. What does the Benedict’s reagent detect? F. What does the IKI solution detect?

G. In what way is a cell membrane similar to the model cell made of dialysis tubing?

H. Is the transport mechanism in the model cell passive or active? Why?

Exercise 2: Diffusion at different temperatures

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Data Table 3: Diffusion of KMnO4 at Various Temperatures and Times
Temperature inside cup	Color of Water
	0 min	5 min

Questions

A. How does temperature affect the rate of diffusion?

B. State a general hypothesis to cover how temperature affects rate of diffusion

Exercise 3: Tonicity and Diffusion

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Data Table 4: Potato Dimensions.
Potato	Before Osmosis (L × W) cm	After Osmosis (L × W) cm	Tonicity Hypertonic, Isotonic, or Hypotonic
Distilled water
10% Sodium Chloride

Questions

A. What is the condition of each potato strip after soaking in the test tubes for an hour? Which one is limp and which one is crisp?

B. How would you explain the difference in the conditions of the potato strips using the concept of tonicity?

C. What was the tonicity of the fresh water solution with respect to the potato cells? D. What was the tonicity of the salt water solution with respect to the potato cells?

E. How do the changes in the conditions of the potato strips relate to the wilting of plants?

F. How does keeping vegetables cool slow them from wilting?