Lab 5 – Diffusion, Osmosis and Enzymes
Objective: The objective of this lab is to introduce you to the concepts of diffusion, osmosis and enzyme activity.
Reading Assignment: Read 4.9 and 5.4; Diffusion and Osmosis and How Enzymes Work from the textbook Essentials of the Living World.
For this lab you will need to supply the following materials:
Kitchen scale (food scale, it can weigh in either ounces or grams)
Microwave
Liquid measuring cup
Teaspoon
Tablespoon (3 Tsp = 1 Tbs)
Several Drinking cups (1 needs to hold at least 2 cups of liquid)
1 Potato
Knife
Blender or Potato masher
Zip lock sandwich bag (not a freezer bag)
Pancake syrup
Salt
Sugar
Vinegar
Hydrogen Peroxide (H2O2)
Solutions to prepare
Sucrose solution – add one tablespoon of sugar to 1 cup of water
Exercise 1 – Diffusion
· In this exercise you will observe the diffusion of water through a semipermeable membrane (a plastic bag)
Step 1. Place ¼ of a cup of pancake syrup into a plastic zip lock bag and seal the bag.
Step 2. Weigh the bag using a small kitchen scale and record the weight on your worksheet.
Step 3. Fill larger cup (2 cup measuring or equivalent) with 1 cup of water. Record the time.
Step 4. Place the syrup bag in the larger cup and leave overnight (12+ hours).
Step 5. Remove the bag, dry it off and weigh it using a small kitchen scale. Record weight on your worksheet and the time you ended the experiment. (Hint: The bag should gain weight. If it loses weight you may have had a puncture. You must redo this exercise).
Step 6. Take a picture of the completed exercise and upload to the worksheet. Make sure it includes the date, your name and a photo ID.
Exercise 2 – Osmosis
· In this exercise you will determine the result of putting cells into solutions of various tonicity.
Step 1. Cut (2) potato slices: 3 inches long, 1 inch wide, 0.5 inches thick.
Step 2. Prepare two coffee cups with the following solutions:
Cup 1 = add one cup of water
Cup 2 = add one cup of water and 1 teaspoon of salt
Step 3. Add one potato slice to each cup and let stand for 1 hour.
Step 4. Remove potato slices and determine if the slice is crisp or limp. Record your observations of the slices on the data sheet.
Step 5. Take a picture of the completed exercise and upload to the worksheet. Make sure it includes the date, your name, and a photo ID.
Exercise 3 – Enzyme Activity
· In this exercise you will observe factors that affect the enzyme activity of catalase. Catalase is found in potato cells.
H2O2 (hydrogen peroxide) 2 H2O + O2 (oxygen gas) when catalase is present.
Step 1. Place the remaining amount of potato in a blender with two tablespoons of water. Blend to a paste. If you don’t have a blender use a potato masher to make the paste.
Experiment 3-1
Step 2. Transfer one tablespoon of the paste to a small cup and add 1 tablespoon of hydrogen peroxide.
Step 3. Mix together by gently rotating the cup clockwise and record your observations on the data sheet
Step 4. Take a picture of the completed exercise and upload to the worksheet. Make sure it includes the date, your name and photo/student ID.
Experiment 3-2
Step 5. Transfer one tablespoon of the paste to a small cup and add 1 tablespoon of sucrose solution.
Step 6. Mix together by gently rotating the cup clockwise and record your observations on the data sheet.
Step 7. Take a picture of the completed exercise and upload to the worksheet. Make sure it includes the date, your name and photo/student ID.
Experiment 3-3
Step 8. Transfer one tablespoon of the paste to a small cup and add 1 tablespoon of vinegar (an acid).

Step 9. Next add 1 tablespoon of hydrogen peroxide.

Step 10. Mix together by gently rotating the cup clockwise and record your observations on the data sheet.

Step 11. Take a picture of the completed exercise and upload to the worksheet. Make sure it includes the date, your name and photo/student ID.

Experiment 3-4

Step 12. Transfer one tablespoon of the paste to a small cup and add 1 tablespoon of water.

Step 13. Microwave on high for 1 minute.

Step 14. Remove from microwave (careful it’s hot) and allow 5 minutes to cool.

Step 15. Next add 1 tablespoon of hydrogen peroxide.

Step 16. Mix together by gently rotating the cup clockwise and record your observations on the data sheet.

Step 17. Take a picture of the completed exercise and upload to the worksheet. Make sure it includes the date, your name and photo/student ID.

Diffusion, Osmosis and Enzymes
Total:
\$8.99