Georgia Highlands College

Laboratory 4

Cell Structure and Function

“Virtual Lab” Instructions

Please follow these instructions to work through this week’s lab at home and via the internet.  You are responsible for all of the material presented in the lab manual. Page numbers reflected are from the 14th edition of Mader's Inquiry into Life.

 

 

Read Introduction on page 41.

4.1 Prokaryotic Versus Eukaryotic Cells

                Read information on page 42.  Be sure to understand the differences between the two types of cells and make observations of a prokaryotic cell using figure 4.1 on page 42.

4.2 Animal Cell and Plant Cell Structure

                Read information on page 43, thoroughly reviewing table 4.1.  Note unique structures at the bottom of page 43 in your lab manual and complete Animal and Plant cell structure/function charts and diagrams on pages 44-45.  Use your text book as needed to identify organelles. 

                Make observation of plant cell structure using figure 4.4 on page 46.

4.3 Diffusion

                Read information of diffusion on p. 47.  Use figure 4.5 to help visualize the process of diffusion.

                Watch the following video on diffusion. 

                Diffusion Video

                Using the following information, calculate the speed of diffusion through a semisolid, liquid and air.  (Be sure to convert the time to “hours”).  Record data in table 4.2 on page 48 and answer the conclusion questions.

Diffusion through a semisolid- dye moved 10 mm in 60 minutes.

Diffusion through a liquid- potassium permanganate moved 30 mm in 10 minutes.

Diffusion through air- perfume moved 15 feet in 1 minute.  (1 foot=305 mm)

               

                Diffusion Across the Plasma Membrane (p. 48)- Read introduction, pay attention to the bold terms.

Read through the experimental exercise on p. 48-49.  And Watch the following video to observe how the water and iodine diffuse across the “plasma membrane” and reacts with the starch.

http://www.youtube.com/watch?v=2Th0PuORsWY

If you were to actually conduct this experiment in the laboratory, a Benedict’s Test (test for sugars) would be positive.  This would indicate that glucose diffused OUT  of the dialysis bag.  As you observed in the video, the starch did NOT diffuse out of the bag, or it would have reacted with the iodine in the beaker, in this set up.  Remember, starch is a polysaccharide; therefore, it is TOO LARGE to pass through the bag.

 

4.4 Osmosis

                Read the introductions for osmosis (p. 49), tonicity (p.50-51) and Elodea (plant cells) on p. 52.  Pay particular attention to what isotonic, hypertonic and hypotonic solutions and all bold terms!

                Watch the following video to reinforce your understanding of osmosis and tonicity.

                http://www.youtube.com/watch?v=qucTUoHAeuY&feature=related

                Watch this video to demonstrate tonicity in respect to animal cells (red blood cells) Note: Crenation and Hemolysis)

                http://www.youtube.com/watch?v=crpeX8nBgJE&feature=related

Here are a couple of videos to demonstrate turgor pressure and plasmolysis in plant cells (Elodea)

http://www.youtube.com/watch?v=VK-_YHakvho&feature=PlayList&p=E189ADC6E5940F0F&index=1 (plasmolysis in elodea)

http://www.youtube.com/watch?v=PFtzs_cUddI (elodea with large central vacuole in a hypotonic solution results in turgor pressure.  Keep in mind these are 3D cells so there are four sides to the cell.  The chloroplasts that you see towards the middle are actually on the top surface.  The large central vacuole is pushing everything out to the four sides of the cell, exerting pressure on the strong cell wall of the plant cell. When you bite into fresh celery or an apple, the “crunch” that you hear is the release of this turgor pressure!)

4.5 pH and cells – OMIT.

Answer Laboratory Review Questions 1-13 on page 56.  Turn these questions in during next weeks lab!

               



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